MINERALS OF THE OCEAN-5 DEEP-SEA MINERALS AND MINING-2 · 2011-01-10 · Fluid inclusions data on physico-chemical parameters of the ore-forming hydrothermal systems at the Galapagos

VNIIOKEANGEOLOGIARWTH-AACHEN UNIVERSITY

BERLIN FREE UNIVERSITY

MINERALS OF THE OCEAN-5 &

DEEP-SEA MINERALS AND MINING-2

Joint international ConferenCe

AbstrActs

28 June — 01 July, 2010

VNIIOkeaNgeOlOgIa

St.PeterSburg, ruSSIa

© ВНИИОкеангеология, 2010© VNIIOkeangeologia, 2010

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programme

28 June, monday9.00 — 10.00 Registration of participants

10.00 — 10.15 Welcome announcements

Yannick Beaudoin, Elaine Baker (UNEP, Norway). Pacific marine minerals and deep sea mining assessment.

Kaiser de Souza, Manoel Barretto da Rocha Neto (Geological Survey of Brazil, Brazil). Geology and mineral resources of the South Atlantic Ocean organized in Geological Information System.

Markus Wengler (International Seabed Authority (ISBA), Kingston, Jamaica). Geographic information management for the international seabed area and its resources.

Coffee-break

Section 1. FerromanganeSe noduleS and cruStSConveners: Peter Halbach, David Cronan

David Cronan (Imperial College, London, Great Britain). Depositional environments of manganese nodules in the Cook Islands EEZ.

Hyun-Bok Lee, Ko Y., Kim J., Yang S., Park C.-K. (Korea Ocean Research & Development Institute (KORDI), Seoul, Korea). Local variations in distribution and composition of ferromanganese nodules in the Korean deep ocean study area, Northeast Equatorial Pacific.

Peter Halbach (Free University Berlin, Germany). Minor and trace metals in Co-rich crusts — concentrations versus water depth.

Lunch

Mikhail Melnikov (Yuzhmorgeologia, Gelendzhik, Russia). Biostratigraphic study of Co-rich crusts at the Magellan seamounts.

Irina Pulyaeva (Yuzhmorgeologia), James Hein (U.S. Geological Survey, USA). Chronostratigraphy of Fe-Mn crusts from the Pacific Ocean.

Tatiana Sedysheva (Yuzhmorgeologia, Gelendzhik, Russia). Destructive influence of radial grabens and peculiarities of Co-rich crusts at the Magellan Seamounts.

Coffee-break

Mikhail Torokhov (GI KSC RAS, Apatity, Russia). Manganese mineralization in host magmatic rocks of the Magellan Seamounts, the Pacific Ocean.

Olga Kolesnik (Pacific Institute of Oceanology, Vladivostok, Russia). Accessory metals in basalts and Fe-Mn crusts from the Belyaevsky Volcano (Japan Sea).

Valentina Sattarova (Pacific Oceanological Institute), Vladivostok, Russia). Rare-earth elements in Fe-Mn crusts from the basin of Honshu (Japan Sea).

Poster session

Jozef Franzen (InterOceanMetal, Slovak Republic). Calculation of the polymetallic nodules resources.

Xiangwen W. Ren, Xuefa. F. Shi, A.M. Zhu, X.S. Fang, J.H. Liu, G.P. Glasby (First Institute of Oceanogra-phy, Qingdao, China). On the depletion of Co in phosphatized Fe-Mn crusts from Magellan Seamount cluster.

Hong Нun Wu (Changsha Institute of Mining Research, Changsha,China). Establishment of the deep-sea soft sediments shearing strength-shearing displacement model.

Lidmila Granina, V.D.Mats (Limnological Institute of SD RAS, Irkutsk, Russia). Iron-manganese nodules in Lake Baikal.

Icebreaker

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29 June, tueSdaySection 2. maSSiVe SulFideS

Conveners: Nikolai Bortnikov, Georgy Cherkashov

Sven Petersen (IFM-Geomar, Kiel, Germany). Seafloor massive sulfide deposits: distribution, ore types, and economic significance.

N.S. Bortnikov, V.A. Simonov, T.V. Shilova, Y. Fouquet.

Physico-chemical parameters of the ore-forming systems at the Logatchev-1 hydrothermal field (data on fluid inclusions).

V.A. Simonov1, V.V. Maslennikov2, T.V. Shilova1, S.P. Maslennikova2 (1Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia, 2 Institute of Mineralogy UrB RAS, Miass, Russia). Fluid inclusions data on physico-chemical parameters of the ore-forming hydrothermal systems at the Galapagos Rift (Pacific Ocean).

Valery Maslennikov, Svetlana Maslennikova (Institute of Mineralogy, Miass, Russia). Study of mineral and trace element zonation in vent chimneys from the Mesozoic Pontides arc basin in comparison with modern black smokers.

Coffee-break

Sergei Andreev, Lidya Anikeeva, Varvara Kazakova, Georgy Cherkashov, Sergei Petukhov, Lidmila Romanova, Nickita Ivanov, Alexeev A., Anna Sotnikova, Elena Mitina, Tatiana Lovchikova. (VNIIOkeangeologia, St.Petersburg, Russia). The map of abundance of sulfide ore in the ocean scale 1:25 000 000.

Mikhail Samovarov, Victor Ivanov, Victor Bel’tenev, Irina Rozhdestvenskaya (PMGE, Russia). Geological structure and sulfide deposits of Semyenov sulfide district (13031’ N, the Mid-Atlantic ridge

Georgy Cherkashov, Larisa Lazareva, Tamara Stepanova (VNIIO, PMGE, Russia). Massive sulfide deposits at Semyenov cluster: mineralogy, age and evolutionLunch.

V. Kuznetsov1, Georgy Cherkashov2, Victor Bel’tenev3, Larisa Lazareva3, Fedor Maksimov1, A. Zheleznov1, N. Baranova1, I. Zherebtsov1 (1St. Petersburg State University, 2VNIIOkeangeologia, 3Polar Marine Geosur-vey Expedition, St. Petersburg, Russia). Semeynov sulfide district: radiochemical study, 230Th/U dating and chronology of sulfide deposits forma-tion.

Irina Melekestseva (Institute of Mineralogy, Miass, Russia). Isotopic composition of massive sulfides from the Semyenov sulfide district.

Sergei Sudarikov, P. Marshak., N. Mikhalchuk (VNIIOkeangeologia, SPbMI, St.Petersburg, Russia). Hydrodynamics and geochemistry of hydrothermal discharge at 13ºN, Mid Atlantic Ridge.

V.Yu. Rusakov1, V.V. Shilov2, I.A. Roshchina1, T.G. Kuzmina1, N.N. Kononkova1 (1GEOKHI, Moscow, 2PMGE, Lomonosov, Russia). Sedimentation history of metalliferous and ore-bearing sediments of the krasnov hydrothermal field (16º38’n, mar) for the last 80 kyr.

Coffee-break

Marc Peters1, Harald Strauss1, Sven Petersen2, Nicolai-Alexeji Kummer3, Christophe Thomazo1,4 (1 Westfäli-sche Wilhelms-Universität Münster, Institut für Geologie und Paläontologie, Münster, Germany2 IFM-GEOMAR, Kiel, Germany 3 TU Bergakademie Freiberg, Lehrstuhl für Hydrogeologie, Freiberg, Ger-many 4 Université Denis Diderot Paris, France). The Palinuro volcanic complex ( the Tyrrhenian Sea): as revealed by multiple sulfur isotope data.

I. Morgunova, Vera Petrova, A. Kursheva., I. Litvinenko, T. Stepanova, Georgy Cherkashov (VNIIOkeangeo-logia, St.Petersburg, Russia). Hydrocarbon markers in the bottom sediments of hydrothermal fields of hydrothermal fields Ashadze-1 and Ashadze-2 (MAR, 13°N).

Sergei I.Petukhov, Petr A.Alexsandrov, Sergei I.Andreev (VNIIOkeangeologia, St.Petersburg, Russia) Deformational model of hydrothermal sulfide ore fields for prediction of hydrothermal activity locations (for different areas of the Atlantic and Indian Oceans).

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Poster session

Irina F. Gablina1, Elena A. Popova2, Tatyana A. Sadchikova1, Victor Ye. Beltenyov3, Valery V. Shilov3 (1Geo-logical Institute RAS, 2VNIIOkeangeologiya, St.Petersburg, Russia, Polar Marine Geological Prospecting Expedition, St.Petersburg, Lomonosov, Russia). Hydrothermal mineral-geochemical zonation in sediments of the Ashadze-1 hydrothermal field (MAR, 13°N).

Ludmila Demina, Olga Bogdanova, Georgy Novikov, Sergei Galkin (Shirshov Institute of Oceanology, Mos-cow, Russia). New data on the low temperature iron deposits at the Broken Spur and Rainbow hydrothermal vent fields, Mid-Atlantic Ridge.

Yuri Laptev (Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia). Kinetics and equilibrium at mixing of fluids: experimental and computed data.

Evgeny Narkevskiy1, A. Gustaytis1 and L. Ermakova2 (1Polar Marine Geosurvey Expedition, 2VNIIOkean-geologia, Saint-Petersburg, Russia). Plume studies at the MAR (cruise 32 of the RV “Professor Logatchev”).

30 June, WedneSdaySection 3. Sea technology

Peter Heinrichs (Aker Wirth GmbH, Germany). Sub-Sea Mining.

Hannes Post (Hydromod, Germany). The potential of marine mineral resources and the related mining technology – a challenge for the Ger-man and the international Industry.

Sup Hong, Hyung-Woo Kim, Jong-Su Choi, Tae-Kyeong Yeu, Soung-Jae Park, Suk-Min Yoon and Chang-Ho Lee (KORDI, Korean Republic). Development of a self-propelled miner and shallow water.

Sven Petersen1, Michael Purcell2, Greg Packard2, Andy Sherrell3, Dorsey Wanless4, Mark Dennett2, Geoff Ek-blaw2, Robin Littlefield2, Neil McPhee2, Michael Mulrooney5, Steven Murphy2, and Marcel Rothenbeck1 (1Ifm-Geomar, Kiel, Germany; 2WHOI, Woods Hole, USA, 3Harbor Branch at Florida Atlantic Univer-sity; 4University of Florida; 5Hydroid Inc., Pocassett, USA). High-resolution side-scan mapping of large areas of the Mid-Atlantic Ridge near 3°N using a fleet of REMUS-type autonomous underwater vehicles.

Coffee break

Section 4. gaS hydrateSYannick Ch. Beaudoin (UNEP/GRID-Arendal, Norway) FROZEN HEAT: GLOBAL OUTLOOK ON METHANE GAS HYDRATES (keynote speaker).

I. GAS HydrAte ModellInG And experIMentSConvener: Tatiana Matveeva, Vladimir R. Belosludov

Vladimir A. Istomin, Valerii G. Kvon (Gazprom VNIIGAZ JSC, Moscow region, Russia), Evgenii M. Chuvilin (MSU, Moscow, Russia), Alexander N. Nesterov (IKZ, Tyumen, Russia). Metastability in gas hydrate systems.

Oleg S. Subbotin (Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk, Russia). Modeling of thermodynamic properties and phase equilibria of mixed methane – ethane gas hydrates CS-I and CS-II.

Vladimir Belosludov, Oleg Subbotin (Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk, Rus-sia), Rodion Belosludov, Hiroshi Mizuseki, Yoshiyuki Kawazoe (Institute for Materials Research, Tohoku University, Japan). Modeling composition of mixed H2-CH4 hydrates of cubic structure I and II at equilibrium with gas phase.

LunCh

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II. nAturAl GAS HydrAteS And relAted proceSSeSConvener: Tatiana Matveeva, Ya. Ch. Beaudoin

Char-Shine Liu (Institute of Oceanography, National Taiwan University). Gas hydrate investigation offshore southwestern Taiwan: an overview.

Xiwu Luan (Institute of Oceanology, Chinese Academy of Sciences (IOCAS), China). Relationship between cold seepage and gas hydrates.

Tamara I. Zemskaya, Tatiana V. Pogodaeva, Olga V Shubenkova, Svetlana M. Сhernitsina (Limnological In-stitute SB RAS, Irkutsk, Russia), Olga P. Dagurova, Savelii P. Buryukhaev, Bair B. Namsaraev (Institute of General and Experimental Biology, SB RAS, Ulan-Ude, Russia), Oleg M. Khlystov (Limnological Institute SB RAS, Irkutsk, Russia); Aleksandr V. Egorov (IO RAS, Moscow, Russia), Aleksey A. Krylov (VNIIOkean-geologia, St-Petersburg, Russia), Gennadii V. Kalmychkov (Vinogradov Institute of Geochemistry, SB RAS, Irkutsk, Russia). Geochemical and microbiological characteristics of sediments near the Malenky mud volcano (Lake Baikal, Russia), with evidence of Archaean intermediate between the marine anaerobic methanotrophs ANME-2 and ANME-3.

Pogodaeva T.V., Zemskaya T.I., Pavlova O.N., Suslova M.Yu., Khlystov O.M. (Limnological Institute SB RAS, Irkutsk, Russia). Peculiarities of biogeochemical characteristics the gas hydrate-bearing sediments of the area of Goloust-noye (lake Baikal, Russia).

Anatoly Obzhirov (POI FEB RAS, Vladivostok, Russia), Tatiana Matveeva (VNIIOkeangeologia, St-Pe-tersburg, Russia), Boris Baranov (IO RAS, Moscow, Russia). Regularities in distribution of gas hydrates in the Sea of Okhotsk.

Coffee break

R.B. Shakirov, A.V. Sorochinskaja, Anatoly I. Obzhirov (POI FEB RAS, Vladivostok, Russia), G.I. Ivanov (SEVMORGEO, St-Petersburg, Russia). Gas-geochemistry features of sediments of the East-Siberian Sea (results from 45 Cruise RV “Akademik M.A. Lavrentyev”, 2008).

Elizaveta Logvina, Tatyana.V. Matveeva, Vera I. Petrova, D.A. Korshunov, V.A. Gladysh (VNIIOkeangeolo-gia, St-Petersburg, Russia), K. Crane (NOOA, Silver Spring, USA), T. Whitledge (University of Alaska Fairbanks, USA. Pockmark-like structures at the Chukchi Sea.

Natalia Pestrikova, Anatoliy Obzhirov (POI FEB RAS, Vladivostok, Russia). Relationship between gas hydrate fields and methane flux in the Sea of Okhotsk.

Sergey Leonov (Gazprom VNIIGAZ JSC, Moscow region, Russia). The prospects of hydrate gas bearing capacity of West Siberia.

Elena Perlova (Gazprom VNIIGAZ JSC, Moscow region, Russia). Unconventional sources of gas and prospects of their development.

Tatiana Matveeva, Alexey Krylov (VNIIOkeangeologia, St-Petersburg, Russia). Gas hydrates of the Russian Arctic seas: distribution and resource potential.

D.A. Korshunov, Elena A. Logvina, Tatiana V. Matveeva (VNIIOkeangeologia, St-Petersburg, Russia). Gas seepage and possibilities for the shallow gas hydrate accumulation at the Barents and Kara seas.

Poster session

N.G. Granin, E.I. Suetnova, L.Z. Granina (Limnological Institute SB RAS, Irkutsk, Russia). Decomposition of gas hydrates in the Lake Baikal: possible causes and consequences.

A.V. Egorov, R.I. Nigmatulin, N.A. Rimskii-Korsakov, A.N. Rozhkov, A.M. Sagalevich, E.S. Chernjaev (IO RAS, Moscow, Russia). Breakup of deep-water methane bubbles in gas hydrate stability zone.

EvEnIng PArty

01 July thurSdayCuLturAL ProgrAm

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PACIFIC MARINE MINERALS AND DEEP SEA MINING ASSESSMENT Beaudoin Yannick, Baker Elaine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Section 1. FerromanganeSe noduleS and cruStSACCESSoRy METALS IN FERRoMANGANESE CRUST AND BASALTS FRoM THE BELyAEVSKy SEAMoUNT, SEA oF JAPAN Astakhova N .V ., Kolesnik O .N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

CoMPoSITIoN oF Fe-Mn CRUSTS FRoM oKHoTSK SEA Baturin G .N ., Dubinchuk V .T ., Rashidov V .A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

DEPoSITIoNAL ENVIRoNMENTS oF MANGANESE NoDULES IN THE CooK ISLANDS EEZ Cronan David S, Guy Rothwell and Ian Croudace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

SoME NoTES To CALCULATIoN oF THE PoLyMETALLIC NoDULES RESoURCES, PRoBLEMS oF THE APPLICATIoN oF THE UNITED NATIoNS INTERNATIoNAL FRAMEwoRK CLASSIFICATIoN FoR RESERVES/RESoURCES Franzen Jozef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

IRoN-MANGANESE NoDULES IN LAKE BAIKAL Granina L .Z ., Mats V .D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

MINoR AND TRACE METALS IN Co-RICH FERRoMANGANESE CRUSTS — CoNCENTRATIoN VERSUS wATER DEPTH Halbach Peter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

ESTABLISHMENT oF THE DEEP-SEA SoFT SEDIMENTS SHEARING STRENGTH-SHEARING DISPLACEMENT MoDEL Hongyun Wu, Xinming Chen, Yuqing Gao, Liuhui Ding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

LoCAL VARIATIoNS IN DISTRIBUTIoN AND CoMPoSITIoN oF FERRoMANGANESE NoDULES IN THE KoREA DEEP oCEAN STUDy (KoDoS) AREA, NoRTHEAST EqUAToRIAL PACIFIC Lee H .-B ., Ko Y ., Kim J ., Yang S ., Park C .-K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

CoNDITIoNS oF Co-RICH MANGANESE CRUSTS FoRMATIoN AT THE MAGELLAN SEAMoUNT BASING oF BIoSTRATIGRAPHIC STUDy Melnikov M .Ye ., Pletnev S .P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

CHRoNoSTRATIGRAPHy oF FE-MN CRUSTS FRoM THE PACIFIC oCEAN Pulyaeva I .A ., Hein James R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

oN THE DEPLETIoN oF Co IN PHoSPHATIZED FE-MN CRUSTS FRoM MAGELLAN SEAMoUNT CLUSTER Ren X .W ., Shi X .F ., Zhu A .M ., Fang X .S ., Liu J .H ., Glasby G .P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

RARE-EARTH ELEMENTS IN FERRo-MANGANESE CRUSTS FRoM THE EASTERN SEA oF JAPAN SEAMoUNTS Sattarova V .V ., Astakhova N .V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

DESTRUCTIVE INFLUENCE oF RADIAL GRABENS AND PECULIARITIES oF FERRoMANGANESE oRE BEDS oF GUyoTS — THE MAGELLAN SEAMoUNTS, THE PACIFIC oCEAN CASE STUDy Sedysheva T .Ye ., Melnikov M .Ye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

MN MINERALIZATIoN IN HoST MAGMATIC RoCKS oF THE MAGELLAN SEAMoUNTS, THE PACIFIC oCEAN Torokhov M .P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

METALLoGENIC PoTENTIAL oF oCEAN INTRAPLATE ENDoGENIC ACTIVITy Yubko V .М . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

contentSauthoreS are liSted in alphabetic order inSide oF the SechionS

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Section 2. maSSiVe SulFideSTHE MAP oF ABUNDANCE oF SULFIDE oRE IN THE oCEAN SCALE 1:25 000 000 Andreev S .I ., Anikeeva L .I ., Kazakova V .E ., Romanova L .I ., Cherkashov G .A ., Petukhov S .I ., Sotnikova A .S ., Mitina E .S ., Lovchikova T .L ., Ivanov N .K ., Alekseev A .M . . . . . . . . . . . . . . . . . . 48

PHySICo-CHEMICAL PARAMETERS oF THE oRE-FoRMING SySTEMS AT THE LoGATCHEV-1 HyDRoTHERMAL FIELD (DATA oN FLUID INCLUSIoNS) Bortnikov N.S., Simonov V.A., Shilova T.V., Fouquet y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

MASSIVE SULFIDE DEPoSITS AT SEMyENoV CLUSTER: MINERALoGy, AGE AND EVoLUTIoN Cherkashov G., Lazareva L., Stepanova T.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

NEw DATA oN THE Low TEMPERATURE IRoN DEPoSITS AT THE BRoKEN SPUR AND RAINBow HyDRoTHERMAL VENT FIELDS, MID ATLANTIC RIDGE Demina L .L ., Bogdanova O .Yu ., Novikov G .V ., Galkin S .V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

HyDRoTHERMAL MINERAL-GEoCHEMICAL ZoNATIoN IN THE SEDIMENTS oF THE ASHADZE-1 HyDRoTHERMAL FIELD (MAR, 13°N) Gablina I .F ., Popova E .A . , Sadchikova T .A ., Beltenyov V .Ye ., Shilov V .V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

SEMENoV HyDRoTHERMAL NoDE (13031’ N, MID-ATLANTIC RIDGE): RADIoCHEMICAL STUDy, 230Th/U DATING AND CHRoNoLoGy oF oRE FoRMATIoN Kuznetsov V ., Cherkashov G ., Bel’tenev V ., Lazareva L ., Maksimov F ., Zheleznov A ., Baranova N ., Zherebtsov I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

KINETICS AND EqUILIBRIA AT MIxING oF FLUIDS: ExPERIMENTAL AND CoMPUTED DATA Laptev Yu ., Novikova S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

MESoZoIC BLACK SMoKERS IN PoNTIDES INTRA ARC BASIN oF THE TETHyS PALAEooCEAN Maslennikov V .V ., Maslennikova S .P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

SULFUR ISoToPIC CoMPoSITIoN oF MASSIVE SULFIDES FRoM THE SEMENoV HyDRo-THERMAL CLUSTER, 13°31’ N, MAR Melekestseva I .Yu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

SoURCES AND GENESIS oF HyDRoCARBoNS IN THE BoTToM SEDIMENTS oF HyDRoTHERMAL FIELDS ASHADZE-1 AND ASHADZE-2 (MAR, 13°N) Morgunova I .P ., Petrova V .I ., Kursheva A .V ., Litvinenko I .V ., Stepanova T .V ., Cherkashev G .A . . . . . . . . . . . . . . . .74

THE RESULTS oF HyDRoPHISICAL ExPLoRATIoNS IN THE ATLANTIC oCEAN DURING THE 32TH CRUISE oN THE RV “PRoFESSoR LoGACHEV” Narkevskiy E ., Gustaytis A . and Ermakova L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

THE PALINURo VoLCANIC CoMPLEx (TyRRHENIAN SEA): INoRGANIC AND MICRoBIAL SULFUR CyCLING AS REVEALED By MULTIPLE SULFUR ISoToPE DATA Peters Marc; Strauss Harald, Petersen Sven, Kummer Nicolai-Alexeji, Thomazo Christophe . . . . . . . . . . . . . . . . . . 79

MoDERN SEAFLooR MASSIVE SULFIDE DEPoSITS: DISTRIBUTIoN, oRE TyPES, AND ECoNoMIC SIGNIFICANCE Petersen Sven . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

DEFoRMATIoN MoDEL oF HyDRoTHERMAL SULFIDE oRE FIELDS FoR PREDICTIoN oF HyDRoTHERMAL ACTIVITy LoCATIoNS (FoR DIFFERENT AREAS oF THE ATLANTIC AND INDIAN oCEANS) Petukhov S .I ., Alexsandrov P .A ., Andreev S .I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

SEDIMENTATIoN HISToRy oF METALLIFERoUS AND oRE-BEARING SEDIMENTS oF THE KRASNOV HyDRoTHERMAL FIELD (16º38’N, MAR) FoR THE LAST 80 KyR Rusakov V .Yu ., Shilov V .V ., Roshchina I .A ., Kuzmina T .G ., Kononkova N .N . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

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NEw DATA oN CoMPoSITIoN oF SULFIDE oRES IN «SEMyoNoV» oRE CLUSTER Samovarov M .L ., Ivanov V .N ., Beltenyov V .Ye ., Rozhdestvenskaya I .I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

FLUID INCLUSIoNS DATA oN THE PHySICo-CHEMICAL PARAMETERS oF THE oRE-FoRMING HyDRoTHERMAL SySTEMS AT THE GALAPAGoS RIFT (PACIFIC oCEAN) Simonov V .A ., Maslennikov V .V ., Shilova T .V ., Maslennikova S .P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

HyDRoDyNAMICS AND GEoCHEMISTRy oF HyDRoTHERMAL DISCHARGE AT 13o N, MID-ATLANTIC RIDGE Sudarikov S .M ., Marshak P .A ., Mikhalchuk N .N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

PLUToNIC CoMPLEx oF THE MIDDLE-ATLANTIC RIDGE, THE AGE AND MULTISTAGE oF ITS FoRMATIoN Shulyatin O .G ., Andreev S .I ., Beljatsky B .V ., Trukhalev A .I. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Section 3. Sea technologySUB-SEA DIAMoND MINING Heinrichs Peter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

HIGH-RESoLUTIoN SIDE-SCAN MAPPING oF LARGE AREAS oF THE MID-ATLANTIC RIDGE NEAR 3°N USING A FLEET oF REMUS-TyPE AUToNoMoUS UNDERwATER VEHICLES Petersen Sven, Michael Purcell, Greg Packard, Andy Sherrell, Dorsey Wanless, Mark Dennett, Geoff Ekblaw, Robin Littlefield, Neil McPhee, Michael Mulrooney, Steven Murphy, and Marcel Rothenbeck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

DEVELoPMENT oF A SELF-PRoPELLED MINER AND SHALLow wATER TEST Sup Hong, Hyung-Woo Kim, Jong-Su Choi, Tae-Kyeong Yeu, Soung-Jae Park, Suk-Min Yoon and Chang-Ho Lee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Section 4. gaS hydrateSFRoZEN HEAT: GLoBAL oUTLooK oN METHANE GAS HyDRATES Beaudoin yannick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

MoDELING CoMPoSITIoN oF MIxED H2-CH4 HyDRATES oF CUBIC STRUCTURE I AND II AT EqUILIBRIUM wITH GAS PHASE Belosludov V ., Subbotin O ., Belosludov R ., Hiroshi Mizuseki, Yoshiyuki Kawazoe . . . . . . . . . . . . . . . . . . . . . . . . 103

GAS HyDRATE INVESTIGATIoN oFFSHoRE SoUTHwESTERN TAIwAN: AN oVERVIEw Char-Shine Liu, Saulwood Lin, Yunshuen Wang, San-Hsiung Chung and Song-Chuen Chen . . . . . . . . . . . . . . . .104

INVESTIGATIoN oF GAS HyDRATE FoRMATIoN IN FRoZEN AND THAwING GAS SATURATED SEDIMENTS Chuvilin E ., Lupachik M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

BREAKUP oF DEEP-wATER METHANE BUBBLES AND GAS HyDRATE FoRMATIoN Egorov A .V ., R .I . Nigmatulin, N .A . Rimskii-Korsakov, A .N . Rozhkov, A .M . Sagalevich, E .S . Chernjaev1 . . . . . 109

DECoMPoSITIoN oF GAS HyDRATES IN BoTToM SEDIMENTS oF LAKE BAIKAL: PoSSIBLE CAUSES AND CoNSEqUENCES Granin N .G ., Suetnova E .I ., Granina L .Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

METASTABILITy IN GAS HyDRATE SySTEMS Istomin V .A ., Kvon V .G ., Chuvilin E .M ., Nesterov A .N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

GAS SEEPAGE AND PoSSIBILITIES FoR THE SHALLow GAS HyDRATE ACCUMULATIoN AT THE BARENTS AND KARA SEAS Korshunov D .A ., Matveeva T .V ., Logvina1 E .A ., Rekant P .V ., Shkarubo S .I . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

PoCKMARK-LIKE STRUCTURES IN THE CHUKCHI SEA Logvina E .A ., Matveeva T .V ., Petrova V .I ., Korshunov D .A ., Gladysh V .A ., Crane K ., Whitledge T . . . . . . . . . . . . 116

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GAS HyDRATES oF THE RUSSIAN ARCTIC SEAS: DISTRIBUTIoN AND RESoURCE PoTENTIAL Matveeva T ., Krylov A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

REGULARITIES IN THE DISTRIBUTIoN oF GAS HyDRATES IN THE SEA oF oKHoTSK Obzhirov A ., Baranov B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

THE UNCoNVENTIoNAL GAS SoURCES AND PRoSPECTS oF THEIR DEVELoPMENT Perlova E .V ., Leonov S .A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

THE wEST– IBERIA HyDRATES-BEARING PRoSPECTS Perlova E .V ., Leonov S .A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

RELATIoNSHIP BETwEEN GASHyDRATE FIELDS AND METHANE FLUx IN THE SEA oF oKHoTSK Pestrikova N ., Obzhirov A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

PECULIARITIES oF BIoGEoCHEMICAL CHARACTERISTICS THE GAS HyDRATE-BEARING SEDIMENTS oF THE AREA oF THE GoLoUSTNoyE (LAKE BAIKAL, RUSSIA) Pogodaeva T .V ., Zemskaya T .I ., Pavlova O .N ., Suslova M .Yu ., Khlystov O .M . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

GAS-GEoCHEMISTRy FEATURES oF SEDIMENTS oF THE EAST-SIBERIAN SEA (RESULTS FRoM 45 CRUISE RV “AKADEMIK M.A. LAVRENTyEV”, 2008) Shakirov R .B ., Sorochinskaja A .V ., Obzhirov A .I ., Ivanov G .I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

MoDELING oF THERMoDyNAMIC PRoPERTIES AND PHASE EqUILIBRIA oF MIxED METHANE – ETHANE GAS HyDRATES CS-I AND CS-II Subbotin O .S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

CHARACTERISTICS oF SHALLow GAS HyDRATE AND RELATIoNSHIP wITH CoLD SEEPAGE Xiwu Luan, Anatoly Obzhirov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

GEoCHEMICAL AND MICRoBIoLoGICAL CHARACTERISTICS oF SEDIMENTS NEAR THE MALENKy MUD VoLCANo (LAKE BAIKAL, RUSSIA), wITH EVIDENCE oF ARCHAEA INTERMEDIATE BETwEEN THE MARINE ANAERoBIC METHANoTRoPHS ANME-2 AND ANME-3 Zemskaya T .I ., Pogodaeva T .V ., Shubenkova O .V ., Сhernitsina S .M ., Dagurova O .P ., Buryukhaev S .P, Namsaraev B .B ., Khlystov O .M ., Egorov A .V ., Krylov A .A ., Kalmychkov G .V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

11

PACIFIC MARINE MINERALS AND DEEP SEA MINING ASSESSMENT

Yannick Beaudoin, Elaine Baker,

UNEP/GRID-Arendal, Teaterplassen 3, 4836 Arendal, Norway, tel: +47 9542 9247, e-mail: [email protected], [email protected]

The exploitation of deep sea marine minerals, including polymetallic sulphides formed at hydrother-mal sites, is now a near term prospect. A number of private sector and State-sponsored interests are actively examining these potential resources, having identified them as partial replacements to dwindling land based reserves. Exploration work in the Exclusive Economic Zones of many Pacific Island States has increased dramatically over the past decade, with key sites having undergone advanced exploration work and environ-mental impact assessments, leaving them on the verge of development. Despite this upsurge in commercial activity, most Pacific Island States have not concurrently developed the specific policy, legislation and regu-latory framework necessary for the governance and sustainable development of deep sea mineral deposits.

UNEP/GRID-Arendal, along with the Pacific Islands Applied Geoscience Commission, is seeking to bridge the gap between science and policy as it pertains to deep sea mineral resources. Building upon its experience linking environmental protection, socio-economic issues and sustainable resource development, UNEP/GRID-Arendal aims to initially produce a regional Pacific Islands deep sea minerals assessment that would serve as a model for an eventual global assessment. Key themes to be addressed include: 1) a synthesis of scientific knowledge pertaining to the geology of deep sea marine minerals, 2) an examination of potential adverse environmental impacts of improperly regulated development and 3) an examination of the socio-economic benefits and consequences of marine mineral resource development.

This regional assessment is targeted primarily at decision makers tasked with developing national policies for regulating deep sea mineral resource development. It is thus formulated as a standalone compilation pro-viding a concise, science-based foundation upon which balanced policy development can take place, incor-porating input from all appropriate stakeholders. Secondary target groups include: 1) private sector and com-mercial interests logistically supporting the development work, and 2) the local communities which, through good governance, could ultimately benefit economically from development activities, but who alternately could, under poorly regulated regimes, suffer from the effects of the degradation of their environment.

UNEP/GRID Arendal is seeking scientific collaborators to provide content for the assessment report plus financial sponsors to support the cost of the assessment, dissemination of the results and associated capacity development in Pacific Island States.

UNEP/GRID-Arendal’s mission is to provide environmental information, communications and capac-ity building services for information management and assessment. Established to strengthen the United Nations through its Environment Programme (UNEP), our focus is to make credible, science-based knowledge under-standable to the public and to decision-makers to promote sustainable development. We are dedicated to making a difference by exploring how environmental information impacts on decision-making and the environment. We seek to bridge the gap between science and politics.

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Section 1 FERRoMANGANESE NoDuLES AND CRuSTS

ACCESSoRy METALS IN FERRoMANGANESE CRuST AND BASALTS FRoM THE BELyAEVSKy SEAMouNT, SEA oF JAPAN

Astakhova N.V., Kolesnik O.N.

V. I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch of Russian Academy of Sciences, 43 Baltiyskaya St., 690041, Vladivostok, Russia, e-mail: [email protected]

The report provides comparative composition analysis of nonferrous, noble, and rare-earth metal inclu-sions in ferromanganese crust and basalts from the Belyaevsky Seamount located in the Central Basin of the Sea of Japan.

Ferromanganese formations. Ferromanganese formations from the Belyaevsky Seamount are presented by crusts of up to 10 cm thickness, ore slabs, and cement in siliceous-glauconitic-manganese rock. Sedimentary lenses containing the Late Pleistocene foraminifera occur inside the slabs. Manganese content in ferromanganese formations varies from 50 to 23%, and Fe from 5 to 0.04%. Мn/Fe ratio values are between 571 and 9.82 [1; 3].

Electron probe X-ray analysis of the ore crust polished section carried out by means of the JXA-8100 instrument (JEOL Ltd., Japan) showed that the crust has a non-uniform chemical composition. We found manganese plots with Si, Fe, Ba, and sometimes Cr impurity and ferro-siliceous zones (fig. 1). Manganese deposits, as compared with ferro-siliceous ones, are later-formed. Plots with different chemical composition occur as stripes and diverse-shaped patches. Their interfaces are distinct enough. As concludes from data obtained, manganese matrices almost always contain chlorine and sometimes some fluorine.

In ferromanganese crust matrices there are many inclusions of nonferrous (Cu, Zn, Sn, Ni), ferrous (Cr, W, Fe), noble (Ag), and rare-earth (La, Ce, Nd) metal grains existed as native elements, sulfides, sulfates, oxides, intermetallic and oxyhalide compounds. Nonferrous metals are in the form of native intermetallic alloys of copper and zinc or copper and tin, sulfides, according to the data of electron microprobe analysis, represented by chalcopyrite, sphalerite, and probably pentlandite (Fe, Ni)9S8 with erbium impurity (fig. 1a). Moreover, tin is present in oxide form. Grains of ferrous metals are exhibited by intermetallic Fe-Cr com-pounds, frequently with copper and zinc impurity, sulfides, and iron oxides. In addition, we detected grain of tungsten characterized by high titanium and cobalt concentrations. It is likely to be intermetallic W-Ti-Co phase. From among noble metals we identified only numerous grains of silver represented by oxides, sulfides, and probably oxyhalide compounds with chlorine (fig. 1b). Sometimes silver contains copper and zinc ad-mixture. Rare-earth metals in the crust from the Belyaevsky Seamount form their own Ln2O3 и Ln2O3×CrO3 phases, where Ln – La, Ce, and Nd.

Fig. 1. Grains of accessory metals in ferromanganese crust from the Belyaevsky Seamount.Footnote. Abbreviations at the figure stand for: BM (?) – bacterial mats, REEs – rare-earth elements.

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Basalts. Microprobe analysis of basalt polished sections indicates that the latters as well as ferromanga-nese crust contain a plenty of grain inclusions which are presented by nonferrous (Cu, Zn, Sn, Ni, Pb, As), ferrous (Cr, W, Fe, Mn), noble (Ag), and rare-earth (La, Ce, Nd, Pr) metals in the form of native elements, sulfides, sulfates, phosphides, oxides, intermetalloids and oxyhalide compounds. Judging by data of electron probe X-ray analysis, nonferrous metals occur as oxic compounds of copper and zinc or copper and tin, tin and lead oxides, nickel and iron phosphides, native nickel, haloid compounds of lead and sulfides existed in the form of chalcopyrite, arsenopyrite, sphalerite, and presumably chalcocite with lead and tin impurity (fig. 2b). From among noble metals we found only silver, sometimes containing tellurium admixture. This metal constitutes such mineral phases as native element, oxides, and sulfides (fig. 2b). Numerous, mainly fine-sized, grains of light rare earths are supposed to occur in the form of La-Ce-Pr-Nd and La-Ce-Nd compounds, often containing a little lead and nickel. In regard to ferrous metals, we revealed only titanium and iron represented by their native phases, significantly more often by different iron oxides such as ilmenite, titanomagnetite with vanadium, chrome-spinel, rutile (fig. 2b). A few grains of scheelite are also found.

Furthermore, we identified areas with manganese oxic mineralization characterized by layered-open-work-dendritic structure which is resulted from the alternation of Mn-enriched layers and those with Mn-Si, Mn-Si-Al, and Mn-Fe-Si composition. It also should be noted that there are plots, having corresponded to halite composition. Zones of weakness in basalts are accompanied by iron hydroxide mineralization in the form of microstreakes. Spread areas of filamentary structured organic matter which is identical to that in the ore crust are also registered. Plots with different chemical composition have rather distinct boundaries.

Conclusions. The microprobe study of the Belyaevsky Seamount crust polished section indicates nonfer-rous (Cu, Zn, Sn, Ni, Pb, As), noble (Ag), and rare-earth (La, Ce, Nd, Pr) metals aren’t absorbed by ferro-manganese hydroxides from the seawater, but form their own mineral phases such as oxides, sulfides, sulfates, intermetallic compounds or native elements. Taking into account the fact that basalts from the Belyaevsky Seamount contain virtually the same complex of accessory metals compared to the crust, these metals would be supplied to the rocks by a common source. The source is most likely represented by deep mantle ore-bearing fluids. Based on the K-Ar dated Miocene-Pliocene age of the basalts [2] as well as findings of the Late Cenozoic foraminifera in sedimentary lenses inside ferromanganese crusts [3], we can speculate that mag-matic fluid separation within such long-lived volcanic center as the Belyaevsky Seamount has been happening for a long time. The latter presents one of the factors which are responsible for the formation of polymetallic deposits similar to those already observed in calderas and on the slopes of volcanoes in the Philippine Sea.

The research was supported by the World Ocean Federal Programme and the FEB RAS Grant 09-II-EO-07-001.

REFERENCESAstakhova N. V.1. Authigenic minerals of Late Cenozoic sediments East Asian marginal seas. – Vladivostok: Dalnauka. 2007. – 244 pp. (in Russian).Lelikov E. P., Emel’yanova T. A.2. Volcanogenic complexes of the Sea of Okhotsk and the Sea of Japan (compara-tive analysis) // Oceanology. 2007. Vol. 47. No. 2. – PP. 273-281.Skornyakova N. S., Baturin G. N., Gurvich E. G. et al3. . Ferromanganese crusts and nodules from the Sea of Japan // Doklady Akademii Nauk USSR. Vol. 293. No. 2. – PP. 430-434 (in Russian).

Fig. 2. Grains of accessory metals in basalts from the Belyaevsky Seamount.Footnote. Abbreviations at the figure stand for: Act – actinolite, Pl – plagioclase, Q – quartz.

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CoMPoSITIoN oF FE-MN CRuSTS FRoM oKHoTSK SEA

G.N. Baturin1, V.T. Dubinchuk2, V.A. Rashidov3

1P.P. Shirshov Institute of Oceanology RAS, 36, Nakhimovsky Prospect, 117997, Moscow, Russia, e-mail: [email protected] of Mineral Resourses, 29, Staromoneny Per., 109017, Moscow, Russia3Institute of Volcanology and Seismology, Far East Division, RAS, 9, Piip Blvd, Petropavlovsk-Kamchatsky, Russia

In memory of L.A. Anikeeva

The Okhotsk Sea is a site of active tectonic movements, volcanic eruptions, and earth quakes accompa-nied by hydrothermal events resulting in formation of abundant Fe-Mn crusts on numerous sub-sea moun-tains and heights. These formations have been the object of investigation for many geologists seeking to de-cipher the features of hydrothermal fluids, and professor L.A. Anikeeva dedicated a great deal of her efforts for these studies (Anikeeva et al., 2002, 2005, 2008).

Materal and methodsThe present investigation has been undertaken as continuation of previous work done before and cited

in list of references. We studied five representative crust samples which have been recovered by RV “Vulca-nolog” from western slopes of Kuril Islands Arc (Table 1). These samples have been investigated by means of recent methods of analytical electron microscopy in line with elemental analyses using both ICP-MS and wet chemistry methods in the Institute of Oceanology RAS, Institute of Mineral resources, and Institute Technological Problems.

Morfology and mineralogy of crustsThe size and morphology of crusts is variable as well as their thickness which does not exceed 2 to 4 cm.

The upper surface of crusts is uneven and botryoidal and rather hard whereas the appearance of the basis which is usually less hard depends on the substrate relief.

Fig.1. Major crust Mn-minerals as seen under transmitting electron microscope: assemblage of todorokite crystals (solid arrow) and its microdiffraction pattern (lower right), finely dispersed vernadite aggregate (broken arrow),

and asbolane platelet (hatched arrow) and its microdiffraction pattern (upper right).

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The set of minerals identified by microdiffraction method includes the following species: Mn minerals — vernadite, Fe —vernadite, todorokite, asbolane, asbolane-busirite;Fe-minerals — hematite, hydrohematite, ferroxyhyte, magnetite;Others — apatite, quartz, montmorillonite, epidote, and some unidentified clayey material.Vernadite is found as poorly crystallized mass as well as assemblages of globules 1 to 4-5 mkm in cross-

section. Todorokite is fairly well crystallized forming assemblages of acicular needle-like crystals. Hematite may assume the form of scales or spindle-like crystallites 1—2 mkm long. But the major part of Mn and Fe minerals is poorly crystallized looking as amorphous mass giving week micro-diffraction patterns.

The attached microphotograph (Fig. 1) shows the spot of crust where three manganese minerals have been identified by microdiffraction method, namely todorokite, vernadite, and asbolane.

Chemical composition of crustsIn order to facilitate the review of chemical data we choosed to divide the analyzed elements in four

groups: major elements, ore-forming elements, microelements, and rare earth elements, which are pre-sented below.

The chemical composition of these samples is demonstrating rather large fluctuations of their chemical composition including both major and minor elements which is as well typical for other hydrothermal de-posits elsewhere. In particular, the Mn/Fe ratio in our samples is changing from 0.56 to 9.20, and such is the case with a number of other elements, the phenomenon which is worth of being discussed in brief.

DicussionAll investigators who studied the Fe-Mn crusts from the Okhotsk Sea came to conclusion that their for-

mation is more or less directy related to hydrothermal activity (Gavrilenko, Khramov, 1989; Uspenskaya et al., 1989; Anikeeva et al., 2005, 2008; Glasby et al., 2006; Dubinin et al., 2008; Astakhova, 2009; Mikhalik, 2009). Besides, some authors offered several mineralogical and geochemical criteria for discerning traces of hydrothermal material in crusts of mixed hydrothermal-hydrogenous origin (Strakhov, 1965; Toth, 1980; and others).

It is assumed that the major mineralogical feature of hydrothermal influence is todorokite presence which is rather common in the crusts described above. Geochemical features are more abundant includ-ing extremely high or low Mn/Fe ratios, higher than 40 (Mn+Fe)/Ti ratio, low base metal concentrations, including REEs, and excess amounts of alkali elements, as well as Ba, Hg, Mo, and Ag, but the latter is not always the case. As for rare earth elements, the relative excess of Eu, namely positive Eu anomaly is also considered as a direct witness of hydrothermal input.

The above results present evidence that some of these phenomena are really present in Okhotsk Sea crusts which is in line with previous considerations about their hydrothermal or at least mixed hydrothermal-hydrogenetic origin.

The comparison of our results with average values offered previously for composition of hydrothermal crusts (see the table) is showing rather evident discrepancy between two sets of data collected and summa-rized by Russian and Japanese specialists. In general, “Russian crusts” are of higher quality in what concerns their base metal content as compared to “Japanese crusts”. It seems that this difference is related to the fact that the samples used by Russian investigators have been taken from numerous collections of crusts recov-ered from all parts of the world ocean without giving preference to one or another region whereas Japanese colleagues used predominantly material from limited part of the Pacific Ocean. Owing to this situation, the concentration of most elements in described crusts recovered from the marginal sea of the Pacific is nearer to the North Pacific crust average which is not equal to the World Ocean crust average. Anyhow, our samples are essentially depleted in base metals as compared to hydrogenetic Fe-Mn crusts whose composition has been described in detail before (Baturin, 1986, 1988; Anikeeva et al., 2002). Besides, such indicators as todorokite abundance, high (Mn+Fe)/Ti ratio, positive Eu anomaly, and mercury appearance in crusts are unequivocal arguments in favor of their formation under direct influence of hydrothermal solutions. The composition of these solutions might be far from constant in time and space and it is evident that much larger set of data is needed for reconstruction of their nature.

This work was accomplished owing to financial support from Presidium RAS Program № 24, 2010.

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Table 1Chemical composition of crusts

ElementSamples

15-87 17-40 17-41 17-43 24-34 24-33* Aver-I Aver-IIMajor elements, %

MnO 14.2 33.9 14.2 20.0 32.3 15.36 20.31 45.10Fe2O3 14.6 4.20 29. 7 15.8 9.4 18.33 16.83 26.74SiO2 35.0 30.9 26.6 32.7 26.2 32.90 17.49 7.73 Al2O3 10.1 6.4 3.2 6.6 5.3 4.01 4.98 2.97TiO2 0.49 0.28 0.15 0.43 0.25 0.22 0.90 0.23CaO 4.5 2.7 1.3 1.4 3.5 2.19 5.40 3.47MgO 3.1 3.1 1.7 2.7 2.8 2.81 2.63 3.25Na2O 3.1 2.6 2.4 2.9 3.7 2.96 2.36 3.20K2O 1.1 1.7 0.88 1.6 1.4 1.57 1.94 1.21P2O5 0.35 0.20 1.83 0.38 0.23 0.28 2.41 0.29Stot 0.13 0.093 0.11 0.15 0.13 0.04 — 0.064Ba 0.1107 0.2561 0.1846 0.2117 0.0823 0.1500 0.1200 0.1376Sr 0.0419 0.0663 0.0853 0.0462 0.0525 0.0610 0.0800 0.0555Mn/Fe 1.14 9.20 0.56 1.48 4.0 0.99 1.41 1.98(Mn+Fe)/Ti 75 71 360 105 220 195 53 398

Base metals, ppmCu 57.2 40.1 40.2 371 50.4 60 800 228Ni 422 253 533 2259 264 250 2000 287Co 200 75.8 622 456 33.5 30 700 72.3V 230 162 381 330 145 120 400 225Mo 190 231 126 233 133 — 400 327Zn 419 201 624 642 359 400 500 238Pb 18.8 16.4 109 242 9.9 8 500 45

Microelements, ppm Ag 0.12 0.08 0.20 0.11 0.13 — 0.77 0.28As 99.5 37.1 290 78 18 18 100 33.1Be 0.65 0.68 1.0 2.0 0.32 0.3 2.32 —Bi 0.16 0.15 0.62 1.8 0.09 0.09 10.18 —Cd 6.3 11.1 3.4 4.2 1.3 — 6.93 16.1Cr 13.1 33.8 29.9 36.8 242 29 100 47.8Cs 2.0 2.6 1.3 2.0 1.3 — 4.83 —Ga 25.6 22.1 11.6 22.3 21.2 5 11.75 —Hf 1.0 1.1 0.91 3.9 0.66 0.6 8.62 —Hg 0.49 0.86 0.81 2.4 0.68 — 0. 22 —Li 51 22.9 17.6 57.9 6.2 72 800 436Nb 1.8 2.3 2.7 12.1 2.88 — 54.1 9.9Rb 20.7 22.6 22.0 34.9 24.3 — 23.65 —Sb 15.1 28.9 15.0 36.6 25.6 — 17.01 25.5Sc 16.1 7.4 4.7 11.2 7.1 9.0 11.48 3.8Se 1.6 <0.4 2.7 1.8 <0.4 — - 0.12Sn 0.39 0.66 0.5 1.3 0.44 — 6.93 —Ta 0.14 0.15 0.14 0.33 0.066 0.1 — —Te 0.68 1.2 5.0 <0.03 <0.03 — — —Th 2.0 2.5 3.8 17.2 1.1 — 10.9 0.65Tl 9.5 6.73 4.4 9.3 0.73 — 23.38 —U 2.3 1.8 41.0 3.3 2.3 — 5.6 2.1W 14.8 236 40.3 35.9 42.5 — 400 23Y 23.7 16.3 63.8 42.6 11.8 23 121.36 17.1Zr 36.8 32.7 41.2 193 23.8 67 400 23

Rare earth elements, ppmLa 18.9 14.6 63.6 80.9 7.6 13 133.7 18.9Ce 40.2 40.3 154 447 14.0 28 239.18 16.3Pr 4.3 3.7 14.4 20.7 1.9 3.5 20.00 —Nd 19.2 15.1 61.8 83.1 8.1 15 103.65 7.2Sm 4.4 3.3 13.2 18.3 2.0 3.7 21.64 0.99Eu 1.3 0.71 3.0 3.9 0.63 1.1 5.75 0.28Gd 4.9 3.3 15.0 18.3 2.3 4.2 21.77 —Tb 0.77 0.50 2.3 2.9 0.35 0.7 9.72 0.25Dy 4.3 2.9 12.7 13.1 2.2 3.7 17.92 —Ho 0.94 0.59 2.4 2.4 0.46 0.8 3.62 —Er 2.7 1.7 7.0 6.3 1.5 2.8 12.03 —Tm 0.41 0.24 0.97 0.94 0.21 9.3 1.77 -Yb 2.6 1.6 6.1 6.2 1.4 2.2 12.67 0.78Lu 0.36 0.24 0.90 0.93 0.23 0.3 1.63 0.14TRtot 105.3 88.8 357.4 705.0 43.2 69.3 605.0 —Ce* 0.97 1.18 1.10 2.37 0.79 0.90 0.97 0.56Eu* 1.23 0.94 0.93 0.93 1.29 1.22 1.15 0.98

17

REFERENCES

Anikeeva L.I., Andreev S.I., Kazakova V.I. et al1. . Cobal-rich ores of the World Ocean. St. Petersburg: VNII Orean-geologia, 2002. 172 p. Anikeeva L.I., Gavrilenko G.M., Rashidov V.A. et al2. . Ferromanganese crusts of subsea volcanic Edelshtein Massif and subsea volcano situated west of Paramushir Island (Kuril Islands Arc) // Volcanology and Seismology. 2005. № 6. P. 1-14.Anikeeva L.I., Kazakova V.E., Gavrilenko G.M., Rashidov V.A3. . Ferromanganese formations from West-Pacific transition zone // Proceed. KRAUNZ. Earth Sci. 2008.№ 1. Р.10-31. Baturin G.N4. . Geochemistry of ferromanganese nodules of the Ocean. Moscow: Nauka, 1986. 340 p.Baturin G.N5. . Geochemistry of Manganese and Manganese Nodules in the Ocean. Dordrecht-Boston-Lancaster-Tokyo: D. Reidel, 1988. 342 p. Dubinin A.V., Uspenskaya T.Y., Gavrilenko G.M., Rashidov V.A6. . Geochemistry and the problems of iron-manga-nese formations origin in island arcs of western part of the Pacific Ocean // Geochemistry. 2009. № 12. Р. 1280-1303.Gavrilenko G.M7. . Under-water volcanic and hydrothermal activity as a source of metals in the ferromanganese formations of the island arcs. Vladivostok: Dalnauka, 1997. 165 p.Gavrilenko G.M., Khramov S.V8. . Ferromanganese formations on the submarine slopes of the Ruril Island Arc. Volcanol. Seismol. 1989. № 8. Р. 278-284.Glasby G.P., Cherkashov G.A., Gavrilenko G.M., Rashidov V.A., Slovtsov I.B9. . Submarine hydrothermal activity and mineralization on the Kurile and western Aleutian island arcs, N.W. Pacific // Mar. Geol. 2006. V. 231. p. 163-180.Mikhailik P.E10. . Composition, structure and formation conditions of ferromanganese crusts from the Sea of Japan and Okhotsk Sea. Ref. of Ph.D. dissertation. Vladivostok: Far East Geological Inst 2009. 22 p.. Strakhov N.M11. . About exhalations on mid-oceanic ridges as the source of ore elements in oceanic sediments // Lithology and mineral resources. 1974. № 3. p. 20-37.Toth J.R12. . Deposition of submarine crusts rich in manganese and iron // Bull. Geol. Soc. Amer. 1980. V.91. № 1. Р. 44-54юUspenskaya T.Y., Gorshkov A.I., Gavrilenko G.M., Sivtsov A.V13. . Ferromanganese crusts and nodules of Kuril Is-lands Arc: their structure, composition and origin // Lithology and mineral resources. 1989. № 4. P. 30-40.Usui A.., Someya M14. . Distribution and composition of marine hydrogenetic and hydrothermal manganese deposits in the northwest Pacific // Manganese mineralzation: geochemistry and mineralogy of terrestrial and marine de-posits. Geol. Soc. Spec. Publ. 1997. № 119. P. 177-198.

Note: sample* after Anikeeva et al., 2008. Aver.I and Aver.II are the average compositions of hydrother-mal Fe-Mn deposits of Recent ocean according to Anikeeva et al., 2002, and Usui, Someya, 1997.

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DEPoSITIoNAL ENVIRoNMENTS oF MANGANESE NoDuLES IN THE CooK ISLANDS EEZ

David S Cronan1, Guy Rothwell2 and Ian Croudace2

1Department of Earth Science and Engineering, Imperial College, London SW 2AZ, United Kingdom2National Oceanography Centre, Empress Dock, Southampton SO14 3ZH, United Kingdom

Managanese nodules reach abundances in excess of 30 kg per square meter in the Penryhn Basin cen-tral equatorial South Pacific. In the south of the Basin they rest on dark brown ferromanganiferous clays, whereas in its northern parts the substrate becomes more calcareous and siliceous. Nine box cores represent-ing this variability, each up to about one half meter in length, have been subjected to ITRAX, XRF measure-ment, calibrated by laboratory WD-XRF analysis. ITRAX is an automated core scanning instrument that records optical, radiographic elemental variations in sediment cores at a resolution as fine as 200 microns using photography, x-radiography and XRF analysis. Additional piston and gravity cores have been studied lithostratigraphically. As the sediment in the Penryhn Basin will be badly disturbed during any future man-ganese nodule mining there, a detailed knowledge of their nature is a prerequisite to environmentally sound nodule recovery.

The cores studied were mainly collected along transect at about 158.5’, W between 12’S and the equator. South of about 4’S sediments are uniform brown to dark brown ferromanganiferous pelagic clays averag-ing about 5—7.5%Al, 17—21%Si, 4—7% Fe, and 1—2% Mn. North of about 4’S the sediments becomes progressively more calcareous, initially in the upper parts of the cores as biological productivity increases towards the equator, but by 2.20’S they are calcareous throughout. Finally, north of 2.20’S the cores have increased Si and decreased Ca in their upper parts as biogenic silica co-exists with calcium carbonate as an important sediment builder under highest productivity waters at the equator. Most trace elements are higher in the clays than in the biogenic sediments and show little variation downcore.

The sediments studied from the Penryhn Basin exhibit important differences from those in other pro-jected Pacific manganese nodule mining areas such as the Clarion-Clipperton Zone and the Peru Basin. In the former, siliceous, sediment is the main substrate in areas of high nodule abundance, whereas pelagic clay fills this role in the Penryhn Basin. In the latter, 5—15 cm of oxic brown mud overlies sub-oxic siliceous/calcareous ooze down to below 50 cm.

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SoME NoTES To CALCuLATIoN oF THE PoLyMETALLIC NoDuLES RESouRCES, PRoBLEMS oF THE APPLICATIoN oF THE uNITED NATIoNS INTERNATIoNAL FRAMEwoRK

CLASSIFICATIoN FoR RESERVES/RESouRCES

Franzen Jozef

Interoceanmetal Joint Organization, ul.Cyryla i Metodego 9, 71-541 Szczecin, Poland

International Joint Organization (IOM) is an international consortium set up in April 1987 to survey and explore polymetallic nodule deposits in the open oceans. In 2001 IOM signed a contract with the In-ternational Seabed Authority for exploration of polymetallic nodules in the 75,000 km2 area situated in the eastern part of the Clarion-Clipperton Zone in the eastern equatorial Pacific to prepare commercial devel-opment of the nodules. This paper summarizes the results of IOM’s activities.

An actual question seems the application of the United Nations International Framework Classification for Reserves/Resources for the polymetallic nodules resources evaluation. This paper brings some topics for a discussion concerned to this problem.

1. Interoceanmetal Joint Organization, its history, aims and activitiesThe Interoceanmetal Joint Organization (further IOM) was formed on 27 April 1987, based on the Inter-

governmental Agreement signed by Bulgaria, Cuba, Czechoslovakia, German Democratic Republic, Poland, USSR and Vietnam, and started operation in December that year. In 1989, Vietnam withdrew from the Organi-zation, while in 1991, Germany followed suit in the wake of the unification. In January 1992, Russian Federation took over the responsibilities of the former USSR. On 31 December 1992, Czech Republic and Slovakia as two sovereign states divided the responsibilities of the former Czechoslovakia between themselves. Thus the IOM member states at present are: Bulgaria, Cuba, Czech Republic, Poland, Russian Federation and Slovakia.

IOM is governed by the Council of Official Representatives of IOM Member States. The Council meets twice a year to work out general policies in conformity with relevant provisions of the IOM Statutes and the Intergovernmental Agreement. The IOM has an Auditory Commission as its controlling body, and Direc-tor General as the executive arm. IOM is composed of two departments, one dealing with geological and ecological surveys as a basis of exploration and exploitation, and the other involved in planning, financial, management and economic matters.

On 30 July 1992, the General Secretary of the United Nations awarded IOM and its member states the Certificate of Registration, whereby the IOM’s status has become that of a pioneer investor. The registered pioneer area of IOM covered 150,000 km2. One of the major responsibilities of IOM was a relinquishment of a half of the pioneer area to the International Seabed Authority (further ISA) to be set aside as the common heritage of mankind. This relinquishment was done successful in the years 1994—2001, therefore actual area of the IOM covers 75,000 km2. (See picture 1).

On 29 March 2001 the contract of exploration was signed between ISA and IOM. IOM’s major task was to carry out prospecting in the pioneer area, later on in the contracting area, with the aim of laying grounds for future exploration of polymetallic nodules, the mineral resource of interest. Polymetallic nodule deposits are found on the seafloor at depths 4000—6000 m in many parts of the world’s oceans. However, it is clear at present that the North-East Pacific’s Clarion-Clipperton Fracture Zone is most interesting from the eco-nomic point of view. In the area between Hawaii and Mexico an estimated 34 billion tons of nodules are to be found. The estimated prognostic resources of the major metals are 7,5 billion tons of Mn; 340 million tons of Ni; 265 million tons of Cu and 78 million tons of Co (Morgan, 2000).

The most promising part of the pioneer area of the IOM represents the hexagon, having the following coordinates (turning points):

120° 10’ W, 10o50’ N119o 25’ W, 10o50’ N119o 25’ W, 10o10’ N120o 00’ W, 10o10’ N120o 00’ W, 10o30’ N120o 10’ W, 10o30’ N

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These coordinates represent a total area of 5380 km2, there was carried out a detailed exploration.The data supplied by side-scan sonar, photo-profiling and sediment sampling served to contour nodule

deposits in the area of detailed exploration within which prognostic nodule resources were assessed with reference to parameters used by IOM to estimate usability of the deposits, and assigned to category R2. The deposits meet the following conditions:

— the width of the deposit should be not lower than 700 m;— the area assessed does not include deposits located where the slope angle exceeds 7°.The areas with slope angles higher than 7° cover 950 km2 (17,6%); the areas covered by nodule deposits

meeting the above-listed assessment criteria of usability amounted to 4000 km2. The area explored contains metal-poor (Ni + Cu + Co = less than 2%), intermediate (Ni + Cu + Co =

= between 2—2,75%) and metal-rich nodule deposits (Ni + Cu + Co = more than 2,75%). Most frequent are the metal-rich deposits. Metal-poor deposits consist of type H nodules, intermediate deposits are domi-nated by type HD, and in part type D1 nodules, while metal-rich deposits are dominated by type D and, to a lesser degree, type D1 nodules. The major part of the nodule resources is located within the depth interval of 4300—4450 m.

In the most promising area of 5380 km2 nodules were collected at 101 out of the 104 sampling stations visited. This means on average one station for an area of 51,7 km2.

2. Problems of the application of the United Nations International Framework Classification for Reserves/Resources for the polymetallic nodules resources evaluation

United Nations Economic and Social Council, Economic Commission for Europe (Headquarters Ge-neva) accepted in July 2004 an idea of the application of the United Nations Framework Classification for Reserves/Resources (further UNFC) in the member states. At present an application of this classification is taken up as a recommendation, not as an obligation.

The main principles of this three dimensional classification are generally known. They are three axes:— E (Economic) for an economic evaluation (3 grades)— F (Feasibility) for an evaluation of the feasibility of exploitation (3 grades)— G (Geologic) for an evaluation of the geologic knowledge (4 grades)For example, final evaluation 111 means Proved mineral reserves, 334 means Reconnaissance mineral

resources.For the IOM and other organizations with the similar aims would be very important and useful, to know

the possibilities and limits for the utilization of the UNFC. Kotliński (1995) means, that immediate appli-cation of the principles and procedures of the evaluation of the mineral reserves/resources on the land for the evaluation of the oceanic reserves/resources is not possible and irrational. In his work (Kotliński, 1998) proposed the symbols R-1, R-2, R-3, corresponding with United Nations Classification.

At a first view, taking in consideration one sampling station for an area of 51,7 km2, it seems very plau-sible, to evaluate the nodule deposits in the IOM exploration area with the symbol 334 (Reconnaissance mineral resources). But we do not stop at this hurried evaluation.

In the Classification key for the reserves/resources (Enclosure 4 to the UNFC) we can find 77 questions for a classification and ranking. We will bring here only the questions, relate to the nodule deposits in the IOM area.

Question 18 Were the geological data obtained during a reconnaissance ?Answer If yes and adequate data, then 334. Unclear, maybe a stage of prospecting ?Question 19 Were the geological data obtained during a prospecting ?Answer If yes, then 333.Unclear.

Conclusion — they are two crucial problems:— Is the UNFC applicable for the oceanic nodule deposits ?— The exploration activities in the IOM area belong to a stage of reconnaissance or to a stage of pros-

pecting ?

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REFERENCESKotli1. ński, R.,1995: International law-related aspects of research and exploitation of oceanic seabed, with a particular reference to Interoceanmetal as a Registered Pioneer Investor. In: Problemy rozwojowe techniki okrętowej, materiały sympozjum, PAN, Kom.Tech., Szczecin, 61-68.Kotli2. ński, R.,1998: Geneza i rozmieszczenie złóź kopalin.A.Surowce metaliczne-Konkrecje polimetaliczne. In: Kotliński, R., Szamalek, K.(Eds.) Surówce mineralne mórz i oceanów, Wyd. Nauk.”Scholar”, Warszawa: 127-184 (in Polish).Kotli3. ński, R., 2010: Activities of the Interoceanmetal Joint Organization (IOM) in relation to deep seabed min-eral resources development. Seminar „Seabed: The new frontier”, Exploration and exploitation of deep seabed mineral resources in the Area: Challenges for the International Community, Madrid, 29.Metodika Ministerstva 4. źivotného prostredia Slovenskej republiky pre spracovanie klasifikácie zásob a zdrojov pevných nerastných surovín. MŽP SR Bratislava, 2005 (in Slovak, official document of the Ministry of Envi-ronment of Slovak Republic). Morgan, C.L.5. , 2000: Resource Estimates of the Clarion-Clipperton Manganese Nodule Deposits. In: Cronan, D.S. (ed.) – Handbook of Marine Mineral Deposits, CRC Press, Marine Science Series, Boca Raton, LLC, 145-170.Reports on Activities of the Interoceanmetal Joint Organization in 2009, 2008, 2007, IOM Szczecin.6.

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IRoN-MANGANESE NoDuLES IN LAKE BAIKAL

Granina L.Z., Mats V.D.

The Limnological Institute of SD RAS, Ulanbatorskaya st. 3, Irkutsk, 664033, Russia, e-mail: [email protected]

Lake Baikal can be considered a model of the early stage of ocean formation owing to its large sizes, unique depth (up to 1642 m), and rifting. The oxic stage of diagenesis widely manifested in Baikal sediments is specifi-cally “oceanic”. The Baikal water column is enriched with oxygen, which penetrates into the bottom sediments. As a result, most of the surface bottom sediments are oxidized. In the oxidized sediments, there is intensive di-agenetic accumulation of iron and manganese, which leads to their secondary concentration as enriched Fe and Mn layers, Fe/Mn crusts, and nodules. Intense diagenetic migration is favored by the low rates of sedimentation, low pH values in the sediments, content of organic carbon (Corg) sufficient for diagenesis (~2%), and impos-sibility for authigenic carbonates to form. The thickness of the oxidized layer and its enrichment in Fe and Mn oxides are related to the depth of oxygen penetration into the sediments, which, in turn, is closely related to the sedimentation rates (Granina, 2008). The latter vary over a broad range of values (approximately 2 to 100 cm/kyr); therefore, all stages of accumulation and differentiation of Fe and Mn, up to the formation of nodules, are represented in the oxidized sediments. The Baikal iron-manganese formations (IMF) are classified mainly into shallow- and deep-water ones. Accumulation of Fe and Mn oxides is a biogenic process, which runs with the participation of various genera of microorganisms (Metallogenium, Leptothrix, Siderocapsa, Naumaniella, Ba-cillus, and Pseudomonas) (Zakharova et al., 2008).

In the lake we recognized two types of Fe and Mn diagenesis specific for regions with high (type I) and low (type II) sedimentation rates (Granina et al., 2004). In the first case, iron and manganese are slightly (3 to 16 times, respectively) concentrated at the sediment surface. This is typical of the region near the Selenga delta and of South and Central Baikal, and Maloe More strait. In the second case, Fe and Mn accumulate mainly at the redox boundary within the sediments, where massive layers enriched in Fe and Mn hydroxides form. Such layers are widespread in North Baikal and at the underwater Akademichesky Ridge — regions characterized by low sedimentation rates and deep penetration of oxygen into the sediments. In these layers, the degree of Fe and Mn enrichment relative to the ambient sediments can exceed 10 and 100, respectively. In the regions with higher sedimentation rates, the calculated duration of accumulation of Mn hydroxides in the oxidized sediments var-ies from 10 to 170 years. In North Baikal and at the Akademichesky Ridge, the accumulation of the substantial amount of Mn oxides has been lasting for thousands of years. Thus, Fe and Mn entering the regions with high sedimentation rates are rapidly buried, whereas in the regions characterized by low sedimentation rates, there is a long process of Fe and Mn compounds dissolution accompanied by their redeposition, which leads to the autochthonous accumulation of almost pure hydroxides. As a result, dark-brown or black sedimentary layers enriched in Mn hydroxides and underlying orange-ocheric layers enriched in Fe hydroxides form at the redox boundary in the deep-water sediments. Such distinct zones of Fe and Mn accumulation in the form of soft layers or solid crusts few millimeters to few centimeters thick are widespread at the bottom. We conventionally call them the Baikal deep-water IMF. The Fe layers (crusts) in the Akademichesky Ridge and North Baikal regions intensely accumulate P and As, whereas the Mn layers are enriched mainly in Mo and Cd (Muller et al., 2002). The impurities of Sr, Ca, and Sb are related to the formation of both Fe and Mn layers. The degree of enrichment of Fe or Mn layers is rather high: up to 58 for As, 35 for Mo, 14 for P, and 4–5 for Sr, Sb, and Cd.

The deep-water IMF represent the intermediate stage of nodule formation, as evidenced from the low de-gree of differentiation of their components and the different thicknesses and compactness of the layers (crusts) even within a sample. In these IMF, the average Mn/Fe ratio is ~0.7; however, it can reach 1—4 and, in some cases, even higher (Amirzhanov et al., 1993; Granina, 2008). Thus, the concentrations of Fe and Mn and the degree of Mn enrichment in the deep-water IMF can be commensurate with those in oceanic nodules. However, the specific feature of Baikal is the incompleteness of oxic diagenetic ore formation in deep-water sediments. The small thickness of the oxidized layer (few centimeters) favors the intense dissolution of heavy Fe/Mn crusts plunging into soft mud, which is confirmed by the high concentrations of Fe and Mn in the pore waters of re-duced sediments near the redox boundary (Muller et al., 2002; Granina et al., 2004). The concretions dissolve before transformation into nodules.

The shallow-water IMF as individual crusts and nodules are spread mainly in the littoral zone — at the tops and slopes of underwater rises characterized by decreased sedimentation rates. They occur on compact

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clays, which prevent their submergence into the sediments. Nodules are known on the Murinskaya and Posol’skaya banks, on the slopes of Bol’shoi Ushkanii Island, near Frolikha Bay, and in some other lake regions. These are ferrous formations, which are much poorer in trace elements (Ni, Co, Cu) than the deep-water IMF.

The Baikal IMF are mainly diagenetic and their composition and occurrence are related to the condi-tions of sedimentation in the lake. The only exclusion is nodules of unusual composition from the slope of Bol’shoi Ushkanii Island and Fe/Mn crusts buried deeply in sediments in the Akademichesky Ridge region.

The IMF of hypothetically hydrothermal genesis. The Baikal region is characterized by a high tectonic activity and, correspondingly, intense hydrothermal processes. As a result, this area abounds in products of hydrothermal activity of different ages. However, on the lake bottom, there is the only hydrothermal vent located in Frolikha Bay (North Baikal). The vent site is characterized by the highest for the lake heat flux from the bottom, specific and diverse bottom fauna, anaerobic conditions in surface sediments resulted from intense methane genesis (Granina, 2008). Thus, Fe and Mn oxides cannot form in these sediments. Until recently, there have been no data on the participation of hydrothermal components in the formation of Fe/Mn nodules in Baikal, though this was earlier assumed (Bukharov, Fialkov, 1996) for the laminated globular nodules sampled on the northern underwater slope of Bol’shoi Ushkanii Island. These nodules are specific by a curiously high concentration of Mn and a high Mn/Fe ratio (Amirzhanov et al., 1993; Bukharov, Fi-alkov, 1996). They are significantly enriched in Co, Ni, Cu, and, particularly, Ba. Nodules were found at the intersection of neotectonic faults, where the near-bottom waters are characterized by increased electric conductivity, and this suggests (Bukharov, Fialkov, 1996) their genetic relationship with low-temperature (up to 100°C) hydrothermal fluids. Recently we investigated one of such nodules by a complex of modern meth-ods, which permitted to study distribution of metals and phases in the nodule and degree of its enrichment with metals on microscale (Manceau et al., 2007). It has been established that Ba in microlayers is related to psilomelane, and Na, to vernadite. The fluctuations of Ba concentrations are, most likely, due to the periodic percolation of hydrothermal waters, which controls the formation of psilomelane or vernadite microlayers, whereas Ni isomorphically replaces Mn. The calculated modules Mn/Fe > 0.5 and (Fe + Mn)/Ti = 73 also suggest the presence of hydrothermal substance in the nodule. A great species diversity and new taxa of ben-thic organisms have been revealed in this area, which allowed to suppose that formation of rich and unusual benthic community might be related to a previously unknown discharge of hydrothermal waters at the bot-tom (Takhteev et al., 2001). This is argued for by the found geyserite, a typical hydrothermal product. Thus, Fe/Mn nodules in Baikal might also be of hydrothermal (or mixed) genesis.

Figure. Occurrence of Fe and Mn ores and phos-phorites in the central area of Western Prebaikalia and of Fe/Mn and phosphate-containing nod-ules, buried deeply in the bottom sediments of the adjacent Baikal regions. Land occurrence (А, B): 1 — Fe/Mn ores; 2 — phosphorites; Baikal bot-tom: 3 — stations at which Fe/Mn crusts buried deeply beneath the bottom surface were revealed (Deike et al., 1997); 4 — region of station 6 and other stations at which data discussed in the text were obtained; 5 — station at which Fe/Mn nod-ules of hypothetically hydrothermal origin were found; 6 — station VER 98-1-3, the sediments from which bear buried phosphate-containing U-richest nodules (Fagel et al., 2005).

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The ancient nodules buried in Baikal sediments might have been inherited from IMF that formed and ex-isted for a long time under conditions different from the modern ones. There are thick (up to ~1 cm) Fe/Mn crusts buried deeply (meters) beneath the bottom surface in the Akademichesky Ridge area. The age of such crusts sampled in different cores is about 65—85 ka (Deike et al., 1997; Granina et al., 2003). We considered this type of relics by the example of sediment core from station 6 located in the n-w block of the Akademi-chesky Ridge at a depth of 240 m. Almost all cores comprising deeply buried Fe/Mn crusts described in re-cent publications were sampled in the same region. In the core of st. 6, the sediments are oxidized to a depth of 2 m. Within the thick oxidized layer, the yellow sediment has dark-brown soft Fe/Mn layers (in horizons 7, 160, and 188 cm) and solid crusts (in horizons 171.5, 172, 193.5, and 197 cm). The sediments have ultralow content of Corg (on average, 0.2%), an inert fraction dominate in the composition of organic matter (OM). Inert OM is unable to initiate diagenetic processes, and sediment remains oxidized throughout a great depth. Owing to the deficit of active Corg, the oxidation front moves deep into the sediments, with Fe and Mn lay-ers being redeposited on it. In this core, buried crusts are 20 times enriched in U compared to the ambient sediment. Both U and P enrichment of buried crusts in this area was reported by different authors (Deike et al., 1997; Zhmodik et al., 2001; Fagel et al., 2005 and others).

The U enrichment of Baikal bottom sediments is tentatively associated with the regional U- and Th-ore occurrences, which are widespread in the areas (including ones on the Baikal shores, see Fig.), where Fe and Mn ore and phosphorite occurrences are localized (Troshin et al., 2001). The contents of P, Fe, and Mn in the buried Baikal phosphate-containing crusts are close to their maximum concentrations published for the phosphorites of Western Prebaikalia. These crusts have impurities of trace elements, which is also typical of the land phosphorites.

The origin of deeply buried Fe/Mn crusts is probably related to the tectonic events in this part of the lake. The day surface of Baikal basin with a weathering crust developed there in the Cretaceous-Paleogene and Neogene, subaerial cover, and accompanying ore mineralization was later flooded by the waters of forming basins. According to published data, relics of this surface were revealed on Ol’khon Island, in the Ol’khon region, and at the Baikal bottom—in Maloe More and at the underwater Akademichesky Ridge. The Fe/Mn crusts, including phosphate- and uranium-containing ones, buried deeply in the sediments of Akademichesky Ridge are located in the immediate vicinity of Fe-, Mn-, and P-ore occurrences on the lake shores (Fig.). Some of them, localized in carbonatized sandy rocks, are deposited in primary subaerial sediments. The rest might be the product of material redeposition, which, under the deficit of active Corg in the sediments, resulted in secondary diagenetic lamination as Fe/Mn layers and crusts formed in different horizons of the core. The subaerial genesis is also argued for by the extremely low content of Corg in the am-bient sediments consisting of redeposited ancient red-colored continental deposits and by the high content of carbonates corroding and replacing the surrounding mineral mass. Red-colored rocks are specific for the Upper Miocene-Pliocene deposits, which acquire their color owing to the presence of anhydrous or water-poor Fe oxides.

The apical part of the ridge has been a land till geologically recent time. In the Late Pleistocene, this part, along with the overlapping Paleogene-Neogene deposits containing Fe/Mn crusts, subsided beneath the lake level. The redeposition of Fe and Mn oxides resulted in the formation of Fe/Mn layers and crusts in the lower part of the sedimentary layer. Their age (~100 ka) agrees with the concept of the relationship of this event with the Tyya phase of tectogenesis, which began 150–120 ka before present. The motions of this phase favor the subsidence of the bottom of Baikal depression to the modern depths (Mats et al., 2001). All this indicates a possible relationship of Fe/Mn crusts (including phosphate- and uranium-containing ones) buried deeply in sediments of the central part of Lake Baikal with the Fe-, Mn-, P- and U- land deposits.

REFERENCESGranina L.Z.,1. 2008. Early Diagenesis of the Baikal Bottom Sediments [in Russian]. Izd. SO RAN, Filial “Geo”, Novosibirsk.Zakharova Yu.R., Parfenova V.V., Granina L.Z. et al2. . 2008. Specific ecological features of the distribution of iron and manganese oxidizing bacteria in bottom sediments of Lake Baikal // J. Ecol. Safety. International Scientific Publications 2 (1), 313-322.Granina L., Muller B., Wehrli B.3. 2004. Origin and dynamics of Fe and Mn sedimentary layers in Lake Baikal // Chem. Geol. 205, 55-72.Amirzhanov B.J., Pampoura V.D., Piskunova L.F.4. 1993. Rare elements in the Lake Baikal ferromanganese nodules // IPPCCE Newsletter, No. 7, 25-28.

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Muller B., Granina L., Schaller T. et al5. . 2002. P, As, Sb, Mo, and other elements in sedimentary Fe/Mn layers of Lake Baikal. Env. Sci. Technol. 36 (3), 411-412.Bukharov A.A., Fialkov V.A.6. 1996. The Geologic Structure of the Baikal Bottom [in Russian]. Nauka, Novo-sibirsk.Manceau A., Kersten M., Marcus M.A. et al7. . 2007. Ba and Ni speciation in a nodule of binary Mn oxide phase composition from Lake Baikal // Geochim. Cosmochim. Acta 71, 1967-1981.Takhteev V.V., Bukharov A.A., Proviz V.I.8. 2001. Peculiar bottom fauna in the specific geologic conditions on the northern underwater slope of Bol’shoi Ushkanii Island (Lake Baikal), in: Investigations of Fauna in the East Siberian Water Basins [in Russian]. Irkutsk University, Irkutsk, 3-7.Deike R.G., Granina L., Callender E., McGee J.J.9. 1997. Formation of ferric iron crusts in Quaternary sediments of Lake Baikal, Russia, and implications for paleoclimate // Marine Geology 139, 21-46.Granina L.Z., Mats V.D., Khlystov O.M. et al.10. 2003. Sedimentary Fe/Mn layers in Lake Baikal as evidence of past and present limnological conditions, in: Long Continental Records from Lake Baikal. Springer, Tokyo, 219-229. Zhmodik S.M., Mironov A.G., Grachev M.A. et al.11. 2001. Uraniferous phosphorites in bottom sediments of Lake Baikal // Dokl. Earth Sci. 379A (6), 682-687.Fagel N., Alleman L.Y., Granina L. et al.12. 2005. Vivianite formation and distribution in Lake Baikal sediments // Global Planet. Change 46, 315-336.Troshin Yu.P., Lomonosov I.S., Lomonosova T.K. et al13. . 2001. Geochemistry of ore-forming elements in the de-posits of Cenozoic depressions in the Baikal Rift Zone // Russian Geology and Geophysics. 42 (2), 337-350.Mats V.D., Ufimtsev G.F., Mandel’baum M.M14. . 2001. The Cenozoic of the Baikal Rift Basin. Structure and Geologic History [in Russian]. Izd. SO RAN, Filial “Geo”, Novosibirsk.

27

MINoR AND TRACE METALS IN Co-RICH FERRoMANGANESE CRuSTS — CoNCENTRATIoN VERSuS wATER DEPTH

Halbach P.

FU Berlin Malteser Str. 74 – 100, 12249 Berlin, Germany, e-mail: [email protected]

The fact that metal concentrations in ferromangenes crusts vary with water depth was already reported in former publications (Halbach and Manheim, 1984; Halbach, 1986). In particular, the two metals Co and Ni which are of high economic importance with regard to the metal potential of the crusts, show a very signifi-cant variation to the water depth: both metals significantly decrease with increasing water depth (Fig. 1).

Twelve selected samples of Mn-crusts taken from the Central Pacific (Actlabs data set) were used to regard the depth-dependent behaviour of some metals (Halbach and Marbler, 2008). Figure 2 considers the elements MnO, Ni, Co, Mo as well as Fe2O3, Al2O3, TiO2 and Cu. In addition, the Table 1 shows the linear correlation coefficients for the same data set. Based on these results we distinguish between two groups of metals: (1) the type A elements (Mn, Ni, Co, Mo, W, Te) are controlled by Mn and are inversely related to the water depth with significantly negative correlation coefficients; (2) the type B elements (Fe2O3, Al2O3, TiO2, Cu, Nd) are controlled by Fe and show significantly positive coefficients with water depth. The ele-ment Nd in the Fe-group is representative for the REEs. The respective diagrams (Fig. 2) show that the course of the plots is not always continuous; the calculated regression line with its coefficient of determina-tion (R2) indicates different levels of probability.The Mn-controlled type A group comprises metals which are related to the colloidal Mn-oxide particles either by outer or inner sphere adsorption or by coprecipita-tion. Since the main Mn source is the O2-minimum zone it is plausible that with increasing distance from this water layer the concentrations decrease.

Fig. 1: Co and Ni concentrations vs. water depth (Halbach and Manheim, 1984). Both metals decrease with in-creasing water depth. The diagram also shows that the gradient of decrease is steeper in the upper part of the water column. According to the depth-related concentrations we have defined the depth from 1000 to 2500 m as the

high-quality depth range.

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Fig. 2. Element concentration profiles vs. water depth of 12 selected crust samples from the northern Central Pa-cific. The respective linear equations of the regression line are shown with their coefficients of determination (R2). The Mn-group elements (type A) decrease with increasing water depth, the Fe-group elements (type B) increase

with increasing water depth.

water depth Al2O3 Fe2O3 MnO CaO TiO2 Ni Cu Ga Nb Mo Nd W Te Cowater depth 1

Al2O3 0,58 1 Fe2O3 0,78 0,26 1 MnO -0,76 -0,90 -0,62 1 CaO -0,24 0,41 -0,61 -0,10 1 TiO2 0,85 0,46 0,81 -0,71 -0,41 1

Ni -0,69 -0,56 -0,79 0,83 0,16 -0,73 1 Cu 0,62 0,08 0,56 -0,29 -0,32 0,69 -0,28 1 Ga -0,21 -0,14 -0,56 0,41 0,39 -0,28 0,64 0,15 1 Nb 0,17 0,27 -0,02 -0,16 0,22 0,26 -0,04 0,32 0,46 1 Mo -0,69 -0,74 -0,68 0,88 0,07 -0,60 0,76 -0,18 0,63 0,20 1 Nd 0,77 0,32 0,82 -0,59 -0,37 0,84 -0,69 0,75 -0,14 0,15 -0,53 1 W -0,70 -0,72 -0,72 0,86 0,16 -0,61 0,75 -0,18 0,61 0,19 0,99 -0,56 1 Te -0,79 -0,35 -0,92 0,64 0,65 -0,77 0,70 -0,49 0,48 0,06 0,70 -0,80 0,77 1 Co -0,84 -0,50 -0,85 0,75 0,34 -0,82 0,68 -0,74 0,28 -0,24 0,66 -0,79 0,68 0,81 1

Table 1: Linear correlation coefficients (r) of the element concentrations of 12 samples used for the con-sideration of the depth-dependant composition. The type A Mn-group metals have significantly negative, the type B Fe-group metals significantly positive coefficients.

29

On the other hand, Fe-oxyhydroxide has two deeper water sources: release because of enhancing dis-solution of biogenetic calcareous tests down to the depth range of the CCD (Halbach and Puteanus, 1984) and hydrothermal alteration of the oceanic crust. The influences of these two sources are reflected by the increase of the Fe group metals in crust samples from deeper water. Seawater measurements in the Central Pacific show the contrary vertical distribution especially for Mn, Co, Mo, W, as well as for Fe and Ti in the water column down to 4000 m (Nozaki, 1997). This reflects the removal of these elements from the seawater by the uptake and incorporation into the two different ferromanganese main compounds.

Some elemental plots versus water depth appear to represent a two-gradient model (e.g. Fig. 1). The change in the angle of inclination lies in the depth range of 2200 to 2400 m. A preliminary model to explain this geochemical two-gradient behaviour will be presented.

REFERENCESHalbach, P. and Manheim, F.T.1. (1984): Potential of cobalt and other metals in ferromanganese crusts on seamounts of the Central Pacific Basin. Mar. Min., 4(4), pp. 319-336.Halbach, P. and Puteanus, D.2. (1984): The influence of the carbonate dissolution rate on the growth and com-position of Co-rich ferromanganese crusts from Central Pacific seamount areas. Earth Planet. Sci. Lett., 68, pp. 73-87.Halbach, P.3. (1986): Processes controlling the heavy metal distribution in pacific ferromanganese nodules and crusts. Geol. Rundsch., 75, pp 235-247.Halbach, P. and Marbler, H4. (2008): Marine ferromanganese crusts: Contents, distribution and enrichment of strategic minor and trace elements. BGR-Report, Project No: 211-4500042565, 73 pp. with 25 Figures and 11 Tables, Hannover, 2008.Nozaki Y.5. (1997): A fresh look at element distribution in the North Pacific. http://www.agu.org/eos_elec/97025e.html

30

ESTABLISHMENT oF THE DEEP-SEA SoFT SEDIMENTS SHEARING STRENGTH-SHEARING DISPLACEMENT MoDEL

Hongyun Wu,Xinming Chen, Yuqing Gao,Liuhui Ding

Changsha Institute of Mining Research, Changsha 410012, China, Tel: 86-731-88671-485, e-mail:[email protected]

The shearing strength-shearing displacement model of deep-sea soft sediments is very important to predict the traction and slip ratio of nodule collector, and optimize the running mechanism of nodule col-lector. According to the physical mechanics characters of the deep-sea soft sediments, the 400 sodium mo-lybdate swell soils are selected as the preparation materials of the deep-sea soft sediments, and the demixion preparation method is adopted to simulate the deep-sea soft sediments in the lab, and the shearing test of the rectangle board of 20×50 cm under different grounding pressures is completed in the soil slot. The test result shows that the simulated deep-sea soft sediments have the representative shearing strength-shearing displacement character of brittle soils. Three shearing strength-shearing displacement models of brittle soils are analyzed in the article, and the shearing strength-shearing displacement model being the same with the deep-sea soft sediments based on maximum shearing strength, residual shearing strength, and elastic mod-ules is established, which can offer theoretical support for the structure optimization of running track and the enhancement of the running performance.

1. IntroductionWide deep-sea bed contains abundant mental mines which attract many scientists from various countries

and regions to study and finally develop and utilize the sea bed mental mine resources. Based on former in-vestigation and exploitation result, China Ocean Mineral Resources Research and Development Association applied the development region of 150 thousands square kilometers to the National Seabed Authority of China in March of 1991, and at March 5, 1999, completed the confirmation of the mental nodule diggings of 75 thou-sands kilometers, and established the exploitation technology research plan of multi-mental nodule region, and developed the exploitation technology research of multi-mental nodule region. As the stage research of the multi-mental nodule research plan, the nodule collector (Chen, 2000 & Li, 2001) (made by Changsha Institute of Mining Research) successfully implemented the comprehensive exploitation test on the soft lake bottom of 134m in 2001 (Wang, 2001). In the test, the nodule collector sunk and slid in the original place, which re-strained the running performance and passing performance of the nodule collector on the soft lake bottom.

The predict the traction and the slip ratio of the nodule collector on the soft sediments, and enhance its passing performance and running performance, the relationship between the shearing strength and the shearing distortion of soft sediments needs to be known. The function of the rectangle shearing board to shear the soils flatly under normal load is similar with the function of the track vehicles shearing soils, so the level traction of the rectangle shearing board under appointed normal load can be used to establish cor-responding shearing strength-shearing displacement model.

Therefore, according to the physical mechanics character of soft sediments in the multi-mental nodule diggings of China, the simulation research of lab deep-sea soft sediments is developed, and the shearing test of simulating deep-sea soft sediments is completed, and the shearing strength-shearing displacement model of soft sediments is established, which can offer theoretical references to predict the traction and the slip ratio of the nodule collector on the soft sediments, optimize the running equipment of the nodule collector and enhance the running performance and the passing performance of the nodule collector.

2. Rectangle board shearing test2.1 Simulation of deep-sea soft sedimentsThe physical mechanics characters of deep-sea soft sediments can be describes as follows. The surface

presents flow state, and the flow state, fluidal plastic state, and plastic state change with the increase of depth, and the grain class of over 50% surface sediments is 0.004 mm (Song, 1999, P.47-54), and the original posi-tion test result of average slip resistance (Gao, 2001, P.425-428) is 1~7.8 kPa in 0~30 cm. Therefore, the 400 sodium molybdate swell soils are adopted as the simulated materials of deep-sea soft sediments to prepare the simulated sediments layer lay layer and they can be used to research the shearing strength-shearing dis-placement model of soft sediments.

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2.2 Test method and equipmentsAs seen in Figure 1, under the function of balancing weight, the shearing board sinks to certain depth,

and after it is stable, the hydraulic ram tows the pull rod and drives the shearing board to shear levelly and stimulate the sediments, and the shearing test of the shearing board is completed. The change of the ground-ing pressure is implemented by adjusting the amount of balancing weight.

The piston of the hydraulic ram is connected with the sensor by the whorl, and the sensor connects with flange, and the flange connected with the top end of the pull rod by the bolt to ensure that the pull rod keeps vertically in the traction. The down end of the pull rod connects with the suspension link on the former end of the shearing board by the bold to eliminate the level effect of the piston to the shearing board. The mea-surement data of sensor is the level traction on the shearing board.

The soil slot in the test has the length of 1.8m, the width of 0.8m and the height of 0.6m, and both sides adopt transparent toughened glasses, and in the test, the shearing of simulated sediments can be observed, and the height of the laid simulated sediments is 0.5m.

The rectangle shearing board has the length of 500 mm, the width of 200 mm, and the tooth height of 70 mm which are equidistantly arranged in 4 teeth.

The sensor is the draught-pressure sensor, and the scale is 10KN, and the measurement precision is 0.05%.The level shearing speed of the rectangle board is the traction speed of the hydraulic ram, i.e. 1cm/s, and

the speed keeps constant.

3. Test result and data analysisAfter the balancing weight is loaded, the shearing board sinks naturally, and after it is stable, the sedi-

ments in front of the shearing board are removed to eliminate the influence of the soil resistance. The length and the width of the removed sediments are equal with the length and the width of the shearing board, and the depth is the sinking quantity after loading and stabilizing of the sharing board. The weights of loading balancing weight respectively are 0kg, 25kg and 40kg, and the grounding pressures respectively are 1.0kPa, 3.5kPa and 5.0kPa, and five times of shearing tests are made respectively to obtain the average values of the measurement results.

The measurement data obtained in the shearing test indicates the relationship of the traction and the shearing displacement of simulated sediments, and to acquire the relationship between the shearing strength with the shearing displacement, the traction can be converted to the shearing strength of simulated sedi-ments.

( )2F FA L b h

τ = =+

(1)

Where, F (N) is the traction, A (cm2) is the shearing area, L (cm) is the grounding length, h (cm) is the track tooth height, and b (cm) is the grounding width.

To visually obtain the relationship between the change rule of shearing strength with the shearing dis-placement of sediments, the shearing displacement is the abscissa, and the test data of shearing strength is the longitudinal coordinates, and the relationship curve between the shearing strength and the shearing displacement of sediments under original testing condition is seen in Figure 4, which simulates the curve re-lationships between the shearing strength measurement average values and the shearing displacement under the grounding pressures of 1.0 kPa, 3.5 kPa and 5.0 kPa.

From Figure 4, the change of the shearing strength of soft sediments is consistent with the change of shearing displacement, i.e. the shearing strength of soft sediments increases quickly with the increase of

Fig. 1. Principle Chart of Shearing Test (1—soil slot, 2—simulated sedi-ments, 3—balancing weight, 4—shearing board, 5—flange, 6—sensor, 7—pull rod, 8—suspension link, 10—hydraulic ram)

32

shearing displacement, and quickly descends when achieving the peak value, and slowly reduces to stable residual shearing strength.

According to Figure 4, under the grounding pressures of 1.1kPa, 3.5kPa and 5.0kPa, the shearing strengths of soft sediments all achieve the peak values (respectively 1.21kPa, 1.46kPa and 1.68kPa), and the corresponding shearing displacement is 3.6cm, and their residual shearing strengths respectively are 0.5kPa, 0.85kPa and 1.1kPa.

4. Shearing strength-shearing displacement model of soft sedimentsIn the classic earth pressure theories, two usual representative soils are plastic soils and brittle soils, and

both character curves of shearing strength-shearing displacement respectively are seen in the curve A and the curve B in Figure 5. In Figure 5, the curve A is a smooth shearing strength-shearing displacement curve, and the shearing strength slowly achieves to the maximum shearing strength τmax and the change of shearing

33

strength is small, and the whole curve has no obvious “hump”. In the curve B, the “hump” of the maximum shearing strength τmax occurs, and it possesses significant stable stage of residual shearing strength after yield-ing limitation.

In the measurement data curve of Figure 4, the relationship between shearing strength and shearing displacement of soft sediments has representative character of brittle soils.

Aiming at the mechanical character of brittle soils, Bekker (Bekker, 1956), Wong JY (Wong, 1989), Schwarz (E. Schulte, 200, P.121-131) and Sup Hong (Jong-su Choi, 2003, P.139-143) put forward different shearing strength-shearing displacement models.

Bekker’s model and Wong’s model mainly aim at the soils of earth, and they may not suit for the soft sediments with flow surface and high water content. Bekker’s model is complex and the computation is fussy. Wong’s model defines the relationship between the maxim shearing strength and the residual shearing strength as the sensitive coefficient of soils, which is too qualitative. Schwar’s model firstly introduces the residual shearing strength, and adopt the attenuation index, the destroying coefficient, and the destroying index to represent the influences of the track structure parameters, but the whole model with more param-eters and influencing factors is too complex.

According to Figure 4, the shearing strength of soft sediments quickly increases with the increase of shearing displacement, and different peak values can not be achieved at same shearing displacement, and the shearing strength quickly descends to corresponding stable value of residual shearing strength. In this way, the shearing stress of soft sediments is related with the maximum shearing strength, the residual shearing strength and the shearing elastic module, but they are independent each other. Therefore, it is not difficult to establish the shearing strength-shearing displacement model of soft sediments which takes the maximum shearing stress, the residual shearing strength, and the shearing elastic module as the characters of inflexion,

and takes 1 / mj ke − and / mj ke− as the change characters. The concrete relationship is seen in the formula as fol-lows.

( ) ( ) ( )1 / 1 / /

max Re( ) . . / 1 . 1 1m m mj k j k j kstj e e e e eτ τ τ− − − = − + − −

(5)

Where, j (cm) is the shearing displacement of soils, τmax (kPa) is the maximum shearing strength of soils, τrest (kPa) is the residual shearing strength of soils, km (cm) is the corresponding shearing displacement of the maximum shearing strength.

The advantage of this model is that only the measurement values of parameters including the maximum shearing strength, the residual shearing strength, and the shearing elastic module of the shearing board in the shearing test with appointed grounding pressure are confirmed, the corresponding shearing strength-shearing displacement model can be established, and the shearing strength-shearing displacement model of soft sediments can be simplified largely.

According to the measurement data in Figure 4, under the grounding pressures of 1.1 kPa, 3.5 kPa and 5.0 kPa, the relationships between the shearing strength and the shearing displacement of soft sediments respectively are

( ) ( )( ) ( )( ) ( )

1 / 3.6 / 3.6

1 / 3.6 / 3.6

1 / 3.6 / 3.6

0.98 1 0.5 1 ( 1.0 )

( ) 1.38 1 0.85 1 ( 3.5 )

1.49 1 1.1 1 ( 5.0 )

j j

j j

j j

e e kPa

j e e kPa

e e kPa

σ

τ σ

σ

− −

− −

− −

× − + − = = × − + − = × − + − =

(6)

The formula (6),are simplified largely comparing with the formula (5), which can help to predict, ana-lyze and solve the tractions of vehicle.

To validate the correctness of the model, the measurement data of shearing strength-shearing displace-ment under the grounding pressures of 1.0 kPa, 3.5 kPa and 5.0 kPa are fitted by the formula (5), and the fitting result is seen in Figure 6, and relative coefficients respectively are 0.76, 0.78 and 0.75, which indicates that the model accords with the change rule of shearing strength of soft sediments with the change of shear-ing displacement.

5. Conclusions(1) The soft sediments have representative characters about shearing strength and shearing displacement

of brittle soils, i.e. the shearing strength of soft sediments quickly increases with the increase of shearing dis-placement, and different peak values can not be achieved at same shearing displacement, and the shearing strength quickly descends to corresponding stable value of residual shearing strength.

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(2) According to the measurement values of parameters including the maximum shearing strength, the residual shearing strength, and the shearing elastic module of the shearing board in the shearing test with appointed grounding pressure, the corresponding shearing strength-shearing displacement model can be established as follows.

( ) ( ) ( )1 / 1 / /

max Re( ) . . / 1 . 1 1m m mj k j k j kstj e e e e eτ τ τ− − − = − + − −

(3) The fitting result of the shearing strength-shearing displacement model indicates that this model can be applied for the prediction and solving of the traction of the nodule collector on deep-sea soft sediments.

The research is financed by the sub-item of the Deep-sea Resource Perambulation Technology of COMRA (No. DYXM-115-04-02-03). (Sponsoring information)

REFERENCESBekker, MG .1. (1956). Theory of Land Locomotion. The University of Michigan Press, Library of Congress Card Number 56-10101.Chen, Xin-ming.2. (2000). Technology design of the pilot mining seabed tracked vehicle. Changsha: Changsha Institute of Mining Research.E. Schulte, R. Handschuh, W. Schwarz.3. (2003). Transferability of Soil Mechanical Parameters to Traction Po-tential Calculation of a Tracked Vehicle. The Proceedings of the Fifth ISOPE Ocean Mining Symposium. Tsukuba, Japan. P.121-131.Gao, Yu-qing.4. (2001). Research and development of in-situ test system of the characteristics of physical me-chanics of seabed soft sediments. Conference on China ocean Resource Research and Development Associa-tion. Beijing: COMRA. P.425-428.Jong-su Choi, Sup Hong & Hyuang-Woo Kim.5. (2003). An Experimental Study on Tractive Performance of Tracked Vehicle on Cohesive Soft Soil. The Proceedings of the Fifth ISOPE Ocean Mining Symposium. Tsu-kuba, Japan. P.139-143.Li, Li. 6. (2001). Development of self-propelled seabed tracked vehicle. Changsha: Changsha Institute of Mining Research. Song, Lian-qing.7. (1999). The physical properties of surface sediments in oceanic polymetallic nodule. Acta Oceanologica Sinica. No.6(21). P.47-54.Wang, MH. 8. (2001). Research Report of Lake Test of the Pilot-testing Mining System. China ocean Resource Research and Development Association (COMR R&D). P.71-72.Wong, JY9. (1989). Terramechanics and Off-Road Vehicles, Elsevier Science Publishers B. V., Amsterdam.Wu, Hong-yun,10. Chen Xin-ming & Gao Yu-qing. (2006). The New Principle of In-situ Testing Shearing Strength of Marine Sediment. Mining and Processing Equipment. No.12. P.16-17.

35

LoCAL VARIATIoNS IN DISTRIBuTIoN AND CoMPoSITIoN oF FERRoMANGANESE NoDuLES IN THE KoREA DEEP oCEAN

STuDy (KoDoS) AREA, NoRTHEAST EquAToRIAL PACIFIC

Lee, H.-B., Ko, Y., Kim, J., Yang, S., Park, C.-K.

Deep-sea & marine georesources research department, Korea Ocean Research and Development Institute, Ansan P.O. Box 29, Seoul, 425-600, Korea. Phone: +82-31-400-6379; Fax: +82-31-418-8772; e-mail: [email protected]

The northeastern Pacific shows the highest nodule abundance among the oceans in the world, and thus has been drawing international attention for deep-sea manganese nodule development. The local variations of nodules in abundance, morphology, chemistry, size, and mineralogy have been reported on various scales from thousand kilometers to hundred meters in the Pacific ocean. It is known that local variations in nodule abundance correlate with seafloor topography and ruggedness, sedimentation rates and bottom current ve-locities which are responsible for erosion and redeposition of sediments.

Geophysical survey and chemical studies were performed to reveal fine-scale variation of the distribu-tion and composition of ferromanganese nodules in Korea Deep Ocean Study (KODOS) Area, which is Korea contract area for manganese nodule exploration and is approximately located between 9°—17° N, 125°—136° W, from the Clarion-Clipperton fracture zone in the northeast equatorial Pacific.

Precise depth sounding on the ship track was measured by a single-beam echo sounder (EA-600) which adopts two frequencies of 12 kHz and 38 kHz with resolutions of 40 cm and 10 cm, respectively. For topo-graphic survey of seafloor, a multi-beam echo-sounder, EM-120, was used. A Free Fall Grab was also de-ployed to recover manganese nodules for the resources assessment. Major and minor elemental composi-tions of nodules were analyzed with ICP-AES (Optima 3300DV, Perkin-Elmer Co.).

This paper presents a detailed description of the local variations in distribution and composition of fer-romanganese nodules.

36

CoNDITIoNS oF Co-RICH MANGANESE CRuSTS FoRMATIoN AT THE MAGELLAN SEAMouNTS BASING oN BIoSTRATIGRAPHIC STuDy

Melnikov M.Ye. 1, S.P. Pletnev2

1 SSC «Yuzmorgeologiya», Krymskaya str., 20, Gelendzhik, 353461, Krasnodarsky Krai,the Russian Federation, e-mail: [email protected] POI FEB RAS, Baltiyskaya st., 43, Vladivostok, the Russian Federation, e-mail: [email protected]

Biostratigraphic studies have made a significant contribution to understanding of Co-rich manganese crust genesis in the past decade. The important role was played not only by age determination of crustal sec-tion elements, but also by biostratigraphic dating of seamount’s rocks which are a substrate for overlapping crusts. Selection of development stages of seamounts enables to reconstruct the conditions, where a forma-tion of multiage layers took place.

Determination of age of a ferromanganese crustal and nodule layers at a various areas of the World Ocean was done even earlier [1, 3, 7]. We were managed to date crustal section elements at the Magellan Sea-mounts [5] at the beginning of 90-s. These determinations were executed by I.A. Pulyaeva basing on analysis of calcareous nannoplankton and generalized later in the given scheme [4]. Basic crust section is composed by four layers — Late Paleocene—Early Eocene layer I-1, Middle—Late Eocene layer I-2, Miocene layer II and Pliocene—Quaternary layer III. Basic section, in some cases, is supplemented by relic layers, where two age ranges were selected Campanian — Maastrichtian and Late Paleocene (?). These results have allowed to conclude, that crust formation is a discrete process in a time. Formation of layers is separated by hiatuses with duration of few million ages.

We used the other group of microfossils in this study — planktonic and benthos forams. The last ones proved to be a good indicator of water paleodepth appraisal. The works of 2004—2008 have shown a good reproducibility of results, based on nannoplankton studies. An ability of correct exploitation of each bio-stratigraphic group became evident, where forams analysis is less time-consuming and can be done in a marine on-board conditions.

Numerous biostratigraphic analyses of sedimentary cover for a number of the Magellan Seamount guyots have allowed to determine their sections are composed by rocks of the Late Mesozoic—Cenozoic and loose sediments of the Pliocene-Quaternary age. Age complexes of Aptian-Turonian, Santonian-Maastrichtian, Late Paleocene-Eocene and Miocene were selected in rock samples. First three complexes are composed by ty-pomorphic rocks, including reefogenic and planktonogenic limestones, edaphogenic breccias and fine detrital rocks. In fact, sediments of deep-sea facies were not met. Pelagic sedimentation of planktonogenic limestones took place within upper bathyal and really deep-sea sediments are starting to be met in the Miocene only.

Comparison of age and crustal layer composition with coeval sediments has allowed making interesting conclusions on conditions of ore accumulation. First of all, as judged by presence of reefogenic sediments, summits of guyots were relatively close to a water surface up to the Late Eocene. Therefore, the lower phos-phatized parts of a crustal section (layers I-1 and I-2) were formed at a depth less than 500—600 m. We had reported about this even earlier, basing on the fact that biogenic phosphatization does not happen at big depths. The study of sedimentary section allows us to state that dominant part of crustal development areas was located within mentioned depth range in the period of the Late Paleocene up to the Late Eocene.

Layer I-1 (Late Paleocene—Early Eocene), as judged by thin layer composition, accreted relatively slow. Layer I-2 (Middle—Late Eocene) built up with more high rates and under more active carbonate sedimenta-tion. Sediment flow embarrassed development of the layer, what resulted in branching, distortion, growth damping of separate ore columns. Interstices between these columns were filled by carbonaceous nano-foramineferal afterwards phosphatized sediment.

Formation of relic layers (Campanian-Maastrichtian and Late Paleocene (?)) could take place in even more shallow waters. As judging from separate samples, one has the impression that columns of ore matter are developing in a single space-time interval with algal stromatolites (photic zone). Probably, ores are super-imposed in this case. However, some peculiarities of ore columns interrelations with mentioned structures and clastic component have allowed to suggest their syngenetic development.

Rather interesting to mention, that matter composition of relic layers significantly differs from layer composition of a basic section. Asbolane and hydrogoethite with high admixture of carbonaceous-phosphat-ic matter are predominant in their mineral composition. Reduced concentrations of economic components

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are usual for their chemical composition, whereas barium content is high (by an order more than in other layers). La/Ce ratio is less than 1, etc. Probably, it is the result of other matter source, e.g. — hydrothermal. Relic layer, in this case, could have a limited distribution and do not cover large areas what is typical for crust accumulations starting from the Late Paleocene.

The Oligocene is not represented in crusts. C’est-a-dire, two lower phosphatized layers and two uppers, which are not practically affected by serious alteration, — are separated by hiatus of more than 13 Ma. This correlates well with practically full absence of Oligocene in the sedimentary section within the studied area and has been proved by DSDP drilling at the Magellan Seamounts. Probably, sedimentation took place in the Oligocene, however sediments were destroyed later by some powerful events connected with tectonic and vol-cano-tectonic processes. Transitional zone with marginal seas was actively formed at that time together with establishing of thermohaline circulation of water masses. Probably, these events were those which responsible for significant submergence of guyots with positioning of their summits at a depths close to the modern ones.

Two upper layers were formed evidently in conditions close to the modern ones. They are characterized by porous structure and do not touched by phosphatization. Layer II, formed in the Miocene, grew probably fast, what is witnessed by large elongation of ore columns. Interstices between columns are filled incompact by clayey matter, with small portion of sandy-silt fraction. Sediments of the Miocene at the Magellan Sea-mounts are spread restrictedly. Their thickness in sedimentary cover can reach 80 m, whereas their outcrops over plateau periphery and slopes of guyots are singular, i.e. the most favorable conditions for sediment ac-cumulation were in a central parts of plateaus in the Miocene, whereas at its periphery most likely were zones of ablation and sediment transit, favorable for formation of crusts over exposed parts of a hard rocks. This should explain a wide distribution of layer II over all guyots.

One cannot forget, that powerful volcano-tectonic event took place at the frontier of the Early and Mid-dle Miocene, which influence was traced within the whole Ocean. Hiatus in formation of layer II is coincide with it in time. Main part of a section is dated by the Late Miocene (foram zones N.16 — N.17). Analysis of nannoplankton gives more wide interval — the Middle—Late Miocene [2, 6]. Basal layer part was dated by the Early Miocene with a possible beginning of formation at the end of the Oligocene, i.e. evolution of a single layer could be interrupted by external events.

Starting from the Pliocene, the layer III is forming. It is most probably that conditions at that period were changing insignificantly and were close in general to modern ones. The layer still continues to form over a vast areas at a contemporary time, however it was reported that crust growth was terminated ca. 700ths. years ago. Blanket distribution of the layer resulted in its sampling within different facial environments, where it has dif-ferent structure. Massive varieties are dominant, however radial-columnar ones are similar to that of layer II, finely porous etc. Nevertheless, main features of mineral composition and chemistry are the same.

The data on composition and age of crusts with following reconstructions allow making rather impor-tant conclusion. Half of a crustal section (its lower part) at least was formed at a shallow depth less than 600 m; i.e. evidently, these are the depths of oxygen minimum or upper laid water thickness. The question arises — if the existence of oxygen minimum layer is so important for the formation of ferromanganese crusts on a submarine rises, as it assumed. Basing on data discussed it is quite questionable.

Taylor-Hogg vortexes is a widely discussed and quoted hypothesis during last years in connection with crust formation. It is turn out to be that presence of oxygen minimum layer is not important for the formation of two upper crust layers, because upwelling of deep waters with high content of dissolved О2 already creates oxidizing conditions in near-bottom waters of the whole guyot’s surface.

REFERENCESCowen J.P., DeCarlo E.H., McGee D.L1. . Calcareous nannofossils biostratigraphic dating of a ferromanganese crust from Schumann seamount. – Mar. Geol., 1993, v. 115, p. 289-306.Glasby G.P., Ren X., Shi X., Pulyaeva I.A.2. Co-rich Mn crusts from the Magellan seamounts cluster: the long journey through time // Geo-Mar Lett. – 2007. – v. 27. p. 315-323.Janin M.-Ch.3. The imprints of Cenozoic calcareous nannofossils from polymetallic concretion: biostratigraph-ic significance for two crusts from the central Pacific (Line Islands ridge and Mid-Pacific mountains). – Abh. geol. B.-A., 1987, v. 39, p. 121-141.Melnikov M.Ye4. . Deposits of Co-rich manganese crusts. – Gelendzhik: SSC «Yuzhmprgeologiya», 2005, 230 p. (in Russian).Melnikov M.Ye., Pulyaeva I.A.5. Ferromanganese crusts of the Marcus-Wake and the Magellan Seamounts of the Pacific Ocean: structure, composition, age. – Tokhookeanskaya geologiya, - 1994, № 4, p. 13-27 (in Russian).Pulyaeva I.A.6. Formation stages of ferromanganese crusts at the Magellan Seamounts of the Pacific Ocean. Ph.D.Yhesises, 04.00.10, SPb, 1999, 27 p.Xu Dongyu, Yao De, Chen Zongtuan. 7. Paleo-ocean environments and events of the formation of manganese nodules – Resource geology special issue, 1993, N 17, p. 66-75.

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CHRoNoSTRATIGRAPHy oF FE-MN CRuSTS FRoM THE PACIFIC oCEAN

Pulyaeva, Irina A.1, Hein, James R.2

1SSC “Yuzhmorgeologia”2U.S. Geological Survey, USA

Hydrogenetic Fe-Mn crusts are one of the key types of ferromanganese deposits that occur in the global ocean and are therefore a critical area for research. It is generally accepted [4, 5,7] that the crusts formed by precipitation (and adsorption) of metals from seawater at extremely slow rates (1-10 mm/Ma). Thick crusts provide a complete record of Fe-Mn accumulation on seamounts in the Pacific Ocean starting from the Late Cretaceous. These characteristics make it possible to use crust sections as chronometers for the analysis of the complex evolutionary processes involved in the genesis of oceanic Fe-Mn crust deposits.

In this paper, we establish chronostratigraphic correlations of layered Fe-Mn crust sections from differ-ent parts of the Pacific Ocean and reconstruct the paleoceanographic conditions that influenced crust growth. Litho- and biostratigraphic methods typically used in stratigraphy and correlation of sedimentary deposits are applied to more than 60 samples of layered Fe-Mn crusts selected from Western and Central Pacific seamounts.

Lithostratigraphy of the crusts involved description of the changes in the metal oxides in the sections and identification and systematization of these changes as specific lithologic units, which are defined objectively based on appearance (colour, structural-textural characteristics, degree of diagenesis) and mineralogical and chemical compositions.

Biostratigraphy of the crusts was used to determine the age of crust layers by identification of the rem-nants of calcareous microfossils that are preserved not only in sediments but in Fe-Mn crusts as well. During formation of the metal-oxide layers, calcareous nannofossils have the highest degree of preservation and greatest time-resolution potential. Coccolitophorides and discoasters are more stable in terms of dissolution than foraminifera, and therefore are better preserved. Where these microfossils have been dissolved and re-placed by Fe oxyhydroxides and Mn oxides they leave imprints that are detailed enough to be used to identify genus and species. Using the electron microscope, the microfossil remnants were found to occur not only in carbonates and phosphates that infill interstitial space within the metal-oxide matrix, but also occur within the Fe-Mn-oxide matrix itself. These matrix-supported microfossils make it possible to obtain depositional paleontological information about each unit of metal oxides and determine their ages.

Much has been learned about the structure, composition, and ages of Fe-Mn crusts [e.g., 1, 2, 3, 4, 5, 7, 9, 10, 11, 12]. Our research shows that sections through hydrogenetic Fe-Mn crusts from different areas of the Pacific Ocean show great textural uniformity. Crust layers contain identical assemblages of calcareous nannofossils, which verify their chronostratigraphic efficacy.

The most complete stratatype section occurs in crust sample D11-1 from Lomilik guyot in the Marshall Islands. Five layers are defined based on textures. Representative assemblages of the calcareous nannofos-sil are identified in each layer. Detailed sampling every 5 to 7 mm made it possible to obtain high quality and abundant paleontological information, including characterization of the structure of the assemblages, determination of the frequency of species occurrences, identification of intervals of overlap or concurrence marked by intervals of the co-existence of index-species, all of which allowed the placement of each strati-graphically unit in the time scales of E. Martini and G. Okada & D. Bakri. That procedure produced a detailed stratigraphic scheme showing units dated as Late Paleocene, Early-Middle-Late Eocene, Late Oli-gocene, Middle-Late Miocene, and Pliocene-Pleistocene.

The Late Paleocene unit is the basal layer of the section and has a compact, laminated texture with folia-tion. The lamination is cut by thin (>1—2 mm) interlayer veins of carbonate fluorapatite (CFA). This unit contains an assemblage of calcareous nannofossils characteristic of zones CP8 - CP9a (55.0—52.8 Ma).

The Eocene unit is characterized by a mottled texture. Mottling is produced by the presence of non-met-al-oxide inclusions, which can be up to 10—15% of the unit. The mottles consist of a strongly phosphatized nannoforamiferal material. Three sub-units are distinguished by the way the CFA is distributed in the unit. The lower of the three sub-units contains an assemblage of species that confirms biostratigraphic zones CP9b-CP12 defined as Early Eocene (52.0—48.0 Ma). The assemblage from the middle sub-unit is typical of the Middle Eocene and shows an interval of overlapping species that indicate bio-zones CP13a-CP13b (48.0—46.0 Ma). The simultaneous co-existence of species identified in the CFA inclusions of the upper interval confirms Late Eocene bio-zones CP14b-CP15 (44.0—38.0 Ma).

The metal oxides in the Late Oligocene unit are also characterized by a mottled texture, although the quantity of calcite and CFA is nearly twice as much, 20—25%, as in the Eocene layer. The degree of phos-

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phatization of the nannoforamiferal material is much lower in the Oligocene layer. The composition of the nannofossil assemblage confirms bio-zones CP19-CN1b, which cover the time interval 26.5—21.0 Ma.

The Middle-Late Miocene unit is characterized by metal oxides with increased porosity, columnar tex-ture, and infilling of the porosity by clay-sized material (up to 30%). The Fe-Mn matrix shows laminae rich in imprints of nannofossil shells. The majority of the microfossil assemblage includes co-existing species that confirms bio-zones CN4-CN8 (15.0—7.0 Ma).

A Pliocene-Pleistocene unit caps the section. The metal oxides show a massive texture with densely packed, vertically oriented columns. The microfossil assemblage within the oxides date the section as Plio-cene-Pleistocene (4.0—0.2 Ma).

Hiatuses in crust growth are marked by unconformities between macroscopically distinct layers that are defined by textural differences. These hiatuses in crust growth are dated as 52.8—52.0 Ma (Early Eocene), 46.0—44.0 Ma (Middle Eocene), 38.0—26.5 Ma (Early-Middle Oligocene); 21.0—15.0 Ma (Early Mio-cene); 7.0—4.0 Ma (Late Miocene-Early Pliocene).

The stratigraphic units defined in crust D11-1 reveal a nearly complete history of iron and manganese ac-cretion in the Pacific Ocean. Consequently, this section and similar nearly complete sections found on other seamounts can be considered as the stratatype section and used for chronostratigraphic correlations. Strati-graphic sections of layered crusts from the Magellan seamounts (35 samples), Mid-Pacific seamounts (15 sam-ples), Marshall Is. (5 samples), Johnston I. (1 sample), and Shotoku and Oki-Jokyo seamounts (4 samples) are similar to the stratatype section of crust D11-1 from Lomilik guyot, Marshall Islands; they all have comple-mentary lithologic and paleontological changes. Identical sections found for thick crust samples from the sum-mit of the Magellan guyots duplicate the dates of the metal-oxide units found for the Lomilik guyot crust.

The upper parts of crusts with three or more layers consist of the Miocene and Pliocene-Pleistocene units throughout the study area. However, the growth histories of the lower parts of the crusts vary through-out the region. For example, both the Late Paleocene and Eocene units can be present, or one of them may be missing. The more complete sections are found in crusts from the slopes of seamounts located in the southern part of the area studied in the central Pacific Ocean. In contrast, crusts from seamount slopes lo-cated in the central and northern parts of the area studied are characterized by absence of Middle and Late Eocene units. The Eocene section is also not found in crusts from on some parts of Markus-Wake guyot, where the stratigraphic section is composed of three-layers [10]. A detailed study of a Co-rich Fe-Mn crust from Lamont Guyot in the Marcus-Wake Seamount shows that the crust began forming at 23.3—Ma ago following mass wasting on the slopes of the guyot [12].

The Late Oligocene section is rarely found in the crust sections. This unit is found in single samples from the large collection studied from the Magellan guyots (IOAN and Vlinder) and either overlies the Late Paleocene unit with pronounced unconformity or is the first layer above the substrate. Fe-Mn crust sections dated as Oligocene were found at site 871А on the summit of Limalok guyot, Marshall Islands [1,8]. Similar Oligocene sections are also found in crusts collected from the slopes of atolls in the Tuamotu archipelago [9], located to the South of our study area. The 38.0—26.5 Ma (Early-Middle Oligocene) hiatus defined in the stratatype section is regional in extent and is found in all samples studied.

At the base of some crust sections occurs a breccia in which the Campanian-Maastrichtian carbon-ate matrix was impregnated and cemented by Fe-Mn oxyhydroxides-oxides, probably through replacement (dissolution and immediate precipitation) of a precursor carbonate matrix. However, it cannot be excluded that the carbonate matrix was replaced during a later time period, such as during the Eocene when the crust layers began to grow.

Consistent ages for stratigraphic units in crusts collected at large distance from each other indicate that the process of Fe and Mn oxyhydroxide/oxide accretion on the seamounts of the Western and Central Pa-cific occurred synchronously from the Late Cretaceous through the Pleistocene, with regionally extensive hiatuses in growth between intervals of metal accretion.

The following mineralogical changes with decreasing age of crust layers have been determined. The Mn oxide impregnating the Late Cretaceous breccia is asbolane, whereas the predominant Mn oxide in overlying units is vernadite, except the Late Paleocene unit where the two minerals occur together. The Late Cretaceous, Late Paleocene, Eocene, and Late Oligocene units are phosphatized and are characterized by relatively low major metal contents and by high Mn/Fe ratios. Miocene-Pleistocene units contain much fine-grained detritus, relatively high Fe and Co contents, low Mn/Fe ratios, increased silica, and no CFA.

The evolution of metal-oxide accretion revealed in the stratatype Fe-Mn crust section reflects in general the evolution of the oceanic environment [3, 4, 11, 12]. The main periods of crust accretion were associated with periods of global transgressions, which correspond to times of polytaxic conditions including increased bioproductivity, an expanded oxygen-minimum zone (OMZ), considerable production of biogenic carbon-ate, a relatively high CCD, and high calcium-carbonate dissolution rates, which may have increased the Fe

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oxyhydroxide component in the water column [4]. Hiatuses in crust growth (especially the Early-Middle Oligocene hiatus) coincide with an oligotaxic ocean characterized by cool waters, low productivity, low disso-lution rates of planktonic calcium carbonate, and insignificant Fe oxyhydroxide supply to the water column.

Favourable conditions for Fe-Mn oxyhydroxide/oxide accretion on the slopes of seamounts was deter-mined by their geological/oceanographic evolution, for example history of submergence, extent and intensity of the OMZ, crossing of the equatorial zone of high bioproductivity by plate tectonic movements, chemical composition of water masses, rates of accretion, among others. The Western and Central Pacific seamounts on which the crusts accreted formed during the Cretaceous at paleolatitudes that are equivalent to the present location of French Polynesia [13]. They started migrating in a northwest direction about 110 Ma ago, while experiencing vertical displacement as a result of isostatic subsidence and movement over lithospheric swells, complicated by tectonic rejuvenation [8]. Formation of Fe-Mn crusts on those seamounts occurred long after cessation of volcanism about 60—45 Ma ago, when the seamounts crossed the high-productivity equatorial belt [1]. By that time, the summit and slopes of many guyots had been submerged below the influence of wave action and subsided to the depths of the OMZ. The OMZ played a key role in the acquisition of metals from seawater and other chemical processes. Crusts of Late Paleocene-Eocene ages formed within the relatively shallow-water part of the OMZ in the equatorial zone of high bioproductivity [1]. The geological timing of the passing of a seamount through this equatorial zone may explain the differences in the structure of the Eocene metal-oxide sub-units described above. Crusts of Miocene-Pleistocene ages formed within the deeper part of OMZ [1]. These water depth differences in part controlled the composition of the different aged units.

Processes of phosphatization of Late Paleocene-Eocene and Late Oligocene crust units were related to two major episodes of phosphogenesis in the late Eocene/early Oligocene (~24 Ma) and late Oligocene/early Miocene (~24 Ma) and a minor episode in the Middle Miocene at ~ 15 Ma [6].

This research shows that chronostratigraphy of the regionally consistent sequences of crust layers will greatly aid in the use of hydrogenetic Fe-Mn crusts for geologic and paleoceanographic reconstructions.

REFERENCESBogdanov YA, Bogdanova OY, Dubinin AV et al1. (1995) Composition of ferromanganese crusts and nodules at northwestern Pacific guyots and geological and paleoceanographic considerations. In: Proceedings of the ocean drilling program, Scientific results, vol 144, pp 745-769. Cowen JP, DeCarlo EH, McGee DL2. (1993) Calcareous nannofossils biostratigraphic dating of a ferromanganese crust from Schuman seamount. Mar. Geoal 115: 289-306.Glasby GP, Ren X, Shi X, Pulyaeva IA3. (2007) Co-rich Mn crusts from the Magellan seamounts cluster: the long journey through time. Geo-Mar Lett 27:315-323.Halbach P, Puteanus D4. (1984) The influence of carbonate dissolution rate on the growth and composition of Co-rich ferromanganese crusts from Central Pacific seamount areas. Earth Planet Sci Lett 68:73-87.Hein, J.R.5. , 2006. Geologic characteristics and geographic distribution of potential cobalt-rich ferromanganese crusts deposits in the Area. In Mining cobalt-rich ferromanganese crusts and polymetallic sulphides deposits: Technological and economic considerations. Proceedings of the International Seabed Authority’s Workshop held in Kingston, Jamaica, 31 July-4 August 2006., p. 59-90.Hein, J.R., Yeh, H.-W., Gunn, S.H., Sliter, W.V., Benninger, L.M., and Wang, C.-H.6. , 1993. Two major Ceno-zoic episodes of phosphogenesis recorded in equatorial Pacific seamount deposits. Paleoceanography, v. 8 (2), p. 293-311.Hein JR, Koschinsky A, Bau M, Manheim FT, Kang J-K, Roberts L7. (2000) Cobalt-rich ferromanganese crusts in the Pacific Ocean. In: Cronan DS (ed) Hand book of marine mineral deposits. CRC Press, Boca Raton, Fl, pp 239-279.Larson RL, Erba E, Nakanishi M, Bergercen DD, Licoln JM8. (1995) Stratigraphic, vertical subsidence, and paleolatitude histories of Leg 144 guyots. In: Proceedings of the ocean drilling program, Scientific results, vol 144, pp 915-933. Le Suave et al 9. (1989) Geological and mineralogical study of Co-rich ferromanganese crusts from a submerged atoll in the Tuamotu archipelago (French Polynesia). Mar Geol 87:227-247.Melnikov ME, Pulyaeva IA10. (1995) Ferromanganese crusts deposits on Marcus-Wake and Magellan Seamounts, western Pacific: structure, composition and age. Geol Pac Ocean 11:525-540.Pulyaeva IA11. (1997) Stratification of ferromanganese crusts on the Magellan seamounts. In: Proceedings of 30th International Geological Congress, 8-14 August 1996, Beijing, vol 13, pp11-128.Ren X, Glasby G P, Liu J, Shi X, Yin J12. (2007) Fine-scale compositional variations in a Co-rich Mn crust from the Marcus-Wake Seamount cluster in the western Pacific based on electron microprobe analysis (EMPA). Mar Geophys Res 28:165-182.McNutt MK, Winterer EL, Sager WW, Natland JH, and Ito G13. (1990) The Darwin Rise: a Cretaceous super-swell? Geophys Res Lett 17:110-1104.

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oN THE DEPLETIoN oF Co IN PHoSPHATIZED FE-MN CRuSTS FRoM MAGELLAN SEAMouNT CLuSTER

Ren X.W., X.F. Shi, A.M. Zhu, X.S. Fang, J.H. Liu, G.P. Glasby

Key Laboratory of Marine Sedimentology and Environmental Geology of State Oceanic Administration, First Institute of Oceanography, State Oceanic Administration, 266061, Qingdao, China, e-mail: [email protected]

A Co-rich Fe-Mn crust from Seamount MK in Magellan Seamount cluster was investigated mineral-ogically and geochemically. A section of the Fe-Mn crust was divided into five layers (layers I to V) from sub-strate to surface based on its texture. Layer I and II were phosphatized which was shown by the much higher concentrations of carbonate fluorapatite (CFA), P2O5 and CaO than those of other three layers. Although 11.4% MnO2 of bulk sample are required to reside in todorokite in order to account for Co depletion after phosphatization in layer II, no todorokite was identified in layer II and I from X-ray diffraction patterns. The Gibbs free energy of oxidation of Mn2+ to Mn4+ in vernadite is -14.12kJ/mol under the presumed dissolved oxygen and pH of Pacific seawater in the Cenozoic, which suggests that vernadite in Fe-Mn crusts on sea-mounts in Pacific was not reduced, although the oxygen minimum zone (OMZ) extended onto the slope of these seamounts during phosphatization. The correlations of Co with MnO2, Total Fe (TFe), Al2O3, P2O5, CaO, CFA, and Quartz suggest that, in addition to growth rate, the concentration of vernadite (MnO2) and dilution effects from CFA, TFe and terrigenous detrital minerals are dominant factors controlling the depletion of Co in the phosphatized and non-phosphatized Fe-Mn crusts. Our investigation reveals that the depletion of Co in phosphatized Fe-Mn crust resulted not from the transition from vernadite to todorokite, but from the dilution effects of the CFA on the original deposited Co into vernadite. In addition, the origi-nal Co concentration is controlled by the dilution from TFe, CFA and terrigenous detrital minerals and by growth rate.

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RARE-EARTH ELEMENTS IN FERRo-MANGANESE CRuSTS FRoM THE EASTERN SEA oF JAPAN SEAMouNTS

Sattarova Valentina V., Astakhova Nadezhda V.

V.I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch of Russian Academy of Sciences, 43, Baltiyskaya St., Vladivostok, 690041, Russia, е-mail: [email protected]

The paper deals with the problem of mineral forms of allocation and probable sources of the rare-earth elements (REEs) in ferro-manganese crusts from such seamounts in the eastern Sea of Japan as the Medve-dev Volcano and superimposed basaltic structure on the South Yamato Ridge.

Rare grains occur in matrices with different chemical composition, namely, manganese, siliceous, iron-siliceous. Their size is less than 10 µm. The most enriched with them crusts locate on the slopes of the Med-vedev Volcano, where REEs are present in manganese and siliceous matrices. REEs together with barite fill in microcracks in manganese matrix. Based on the electron microprobe analysis data, they exist in oxide form. On the seamount located within the north-eastern South Yamato Ridge rare earths form both simple lanthanide oxides and complex ones represented by mixed oxides of lanthanides and chromium.

In addition to the above-mentioned mineral forms, REEs are present as an admixture in other minerals. In the Medvedev Volcano crusts in one grain of native iron 1.73% of terbium was detected, in barite we found 0.97% of promethium.

To ascertain sources of REEs we carried out electron microprobe analysis of polished sections made from the Medvedev Volcano basalt sample. Consequently, in the altered rocks multiple inclusions of fine REE grains were identified. Chemical composition of the latters is similar to that in ferro-manganese crust dredged from the same volcano.

Thus, detailed study of the Sea of Japan ferro-manganese crusts carried out by means of the JXA-8100 microprobe analyzer showed that rare earths in observed rocks are not sorbed by iron and manganese hy-droxides, but form their own mineral phases with Ln2O3 and Ln2O3 × CrO3 composition, where Ln denotes La-Ce-Nd and La-Ce-Pr-Nd series of lanthanides, more infrequently La-Ce and La-Ce-Pr.

Source of rare-earth metals is most probably represented by deep-mantle ore-bearing fluids. As known, forming of REE mineral phases in volcanites and overlying ferro-manganese crusts occurs under the influ-ence of such fluids.

The study was carried out with support from the World Ocean Federal Programme and the FEB RAS Grant No. 09-ll-UO-07-001.

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DESTRuCTIVE INFLuENCE oF RADIAL GRABENS AND PECuLIARITIES oF FERRoMANGANESE oRE BEDS oF GuyoTS —

THE MAGELLAN SEAMouNTS, THE PACIFIC oCEAN CASE STuDy

Sedysheva T.Ye., Melnikov M.Ye.

SSC «Yuzmorgeologiya», Krymskaya str., 20, Gelendzhik, 353461, Krasnodarsky Krai, the Russian Federation, e-mail: [email protected]

Volcaniс-tectonic factor is considered often among those controlling ferromanganese ore forming pro-cess at a seamounts. It exerts both constructive and destructive influence on a character of ore beds. Its de-structive influence is more evident. Its significant influence on formation of ore field of the Butakov guyot, has been particularly mentioned.

Western and eastern slopes of the guyot have evident tectonic origin and are characterized by downcast fault origin [1]. Their steep surfaces are composed by undisturbed hard rock outcrops, free of crustal cover-age. These surfaces are represented by most ancient rocks: basalts and different volcaniclastic rocks which are abruptly dominant in the central part, whereas northern part of the western slope — by reefogenic lime-stones of Aptian-Turonian complex. This is, probably, a result of tectonic impact, which removed upper part of sedimentary section at the most areas. Downcast faults destroyed in fact the typical concentric — zonal system of ore beds. Only the central core was preserved. It was localized in the central plateau part and co-incided with a wide spread volcanic edifices at this area. The zone of ore beds stretched along brow of the summit was also preserved. Slope ore beds are practically absent. Crustal covers were preserved only upon flanges of southern and northern spurs.

This is the most striking example. However, evidences of tectonic factor’s influence could be found at any guyot of the Magellan Seamounts. It is manifested e.g. in a wide development of radial grabens. Structures of radial grabens are well traced in bathymetric maps made by multibeam echosounder. They are well segregated by compressing and pips of isobaths meanwhile their direction is changing, and by formation of specific “cou-lisses”. These isobaths form trapezoidal bending towards summit plateau at sites of radial graben structures. These coulisses were formed by two radial dislocations which are oriented across the slope, and displacement plane parallel to the slope. Probably, they were formed in result of block slump from its former position and its destruction in the bottom part of the slope. Displacement plane is characterized usually by high surficial abruptness: slope is more steep here (up to fifty and more degrees) in comparison with that of sides.

Numerous steps with straight line brows and depth drops of 10 up to 20 and more meters are traced by photoprophiling across these slopes. Step surfaces, represented by undisturbed rocks free of ore crusts, could be relatively smooth or striated by linear fosses. Probably, similar surfaces appear to be a polished faults with traces of displacement (sleepwalking) of rock blocks.

Distance between radial disturbances (width of grabens) comprises from 2 to 6 km, deepness of graben in projection to plateau surface — up to 500 m. The structures are exposed in relief up to a depth of 2500—3000 m, sometimes up to 4500 m. Consequently, total height of the structure could be from 1 to 3 km with an average plateau level at 1400—1800 m.

Similar structures are manifested most often at, for example, the north-eastern slope of the Ita-Mai-Tai guyot, northern and south-eastern slopes of the Gelendzhik guyot, at the upper parts of the western and eastern slopes of the Pegas guyot, at the satellite edifices of the Govorov guyot, at the western edifice of the Kocebu guyot. These are the most distinctive examples among others (Fig. 1). There are less distinctive structures with a smaller displacement amplitude, lower depth of intrusion and with a different length of dis-placement planes. Similar structures are located in series sometimes. Radial graben structures were identi-fied at all exposed slopes on the Gordin guyot, however the most powerful is at the southern slope. It is either a combination of two radial grabens, or one complicated graben with different displacement amplitudes of blocks (500 m in western and 800 m in eastern parts) with total extension of 23 km. Series of radial grabens at the mentioned Butakov guyot is located at the northern part of a western slope, with a total distance between radial displacement planes of near 16 km.

Block with younger rocks drive down a slope exhibiting the older ones [1], in contrary to ordinary graben where central block, i.e. dropped part is filled by a younger rocks. The core is composed by oolite limestone of the Aptian-Turonian age, whereas sedimentary breccias of Paleocene-Eocene age are located to the north and south

44

along latitude. Basaltoids of Lower Cretaceous age were sampled at the displacement plane of the Gelendzhik guyot, whereas tuffites and sedimentary breccias of the Paleocene—Eocene age are spread along flanges. Similar situation is at the Pegas guyot, where structures of radial grabens are spread at the eastern and western slopes.

The age of these dislocations is evidently young, because they are well exposed in relief — have recti-linear contours unsmoothed by secondary processes. However, their age in some cases can be determined more precisely. For example, similar structure at the northern slope of the Alba guyot is linked with a chain of volcanic cones at the summit plateau on the continuation of one of displacement of the radial graben. Age determination is based on dating of composing basanites by methods of absolute geochronology and tuffs by forams and nannoplankton dating. Both point to Middle Miocene with confidence [2].

The question arises — how do this structures are influencing to an ore formation system? It is evident, that these displacement forms destroyed previously formed ore beds simultaneously with a destruction of host substrate rocks that results in a reduction of ore areas [3]. They are representing ore-free areas on maps of ore distribution, which are penetrating to zones of powerful crustal ore development. Zones of ore de-struction at the Butakov guyot is estimated by 30—40%, whereas at other guyots these structures are respon-sible for only 5 (rarely — 10%) dislocations.

Influence of volcanic-tectonic factor is not exhausted by enumerated facts. Many other aspects are con-nected with its impact. This factor contributes also into formation of ore crust section, when lower layers of crusts are destroyed partly or totally. Existence of volcanic cones upon slopes (with sometimes detectable age) evidences volcanic-tectonic activity in various time periods. However, unexamined numerous problems are still subsisting. Their study is necessary to obtain additional information for understanding of ore genesis.

REFERENCESMelnikov M.Ye. Influence of Tectonic Factor on Formation of Ferromanganese Crust Accumulations (the 1. Butakov Guyot, the Magellan Seamounts, the Pacific Ocean) (in English).Melnikov M.Ye., Podshuveit V.B., Pulyaeva I.A., Nevretdinov Er.B. Middle Eocene volcanic edifices at the 2. Dal’morgeologiya guyot (the Magellan Seamounts, the Pacific Ocean) //Tikhookeanskaya Geologiya.- 2000.- № 5. - v. 19.- p. 38-46 (in Russian).Sedysheva T.Ye., Khulapova T.M. Peculiarities of slope inclinations within ore beds of Co-rich manganese 3. crusts basing on data of multibeam echosounding // Geology of solid economic minerals of the World Ocean. – Gelendzhik: NIPIOkeangeofizika, 2003.- p. 115-132 (in Russian).

45

MN MINERALIZATIoN IN HoST MAGMATIC RoCKS oF THE MAGELLAN SEAMouNTS, THE PACIFIC oCEAN

Torokhov Mikhail.P.

GI KSC RAS, Apatity, Fersman, 14, 184200, the Russian Federation, e-mail: [email protected]

Mn mineralization is well known in Co-rich ferromanganese crusts of the Magellan Seamounts in the form of vernadite (the main crust forming mineral), asbolane-buserite (I, II), todorokite, birnessite, lithi-ophorite [1]. However, the occurrences of manganese mineralization within host magmatic rocks of guyots has not been previously.

Hydrothermal Mn deposits are well described but are relatively limited in the marine environment and make up less than 1% of the total Mn deposits in the world ocean [2]. Mn crusts occur in all types of active oceanic environments such as at active mid-ocean spreading centers in the depth range 250—5440 m, in back-arc basins in the depth range 50—3900 m, in island arcs in the depth range of 200—2800 m, in mid-plate submarine rift zones in the depth range 1500—2200 m [3] and at hot spot volcanoes in the depth range 638—1260 m [4]. The hydrothermal Mn deposits are characterized by high Mn/Fe ratios and low contents of Cu, Ni, Zn, Co, Pb.

Manganese mineralization at hydrogenous ferromanganese crusts is considered to be a result of sedi-mentation from water thickness in course of Mn2+ oxidation into Mn4+ lower than oxygen minimum layer at a depths of 1800—6000 m. Two valuable theories exist to explain input of manganese into a water thick-ness. First one is a transport of manganese from continental manganese deposits, which are destroying by weathering processes, another a halmyrolisis of basaltic rocks of guyots [1]. However, the existence of hydro-thermal venting at a guyot structures was suggested by Bogdanov et al. [5].

First evidences of Mn-mineralization in magmatic rocks was obtained during the cruises 6-00-6-08 of SSC “Yuzhmorgeologia” in 2000—2010. Amigdaloidal basalts with carbonate fillings have numerous min-eral inclusions with black colour, brown streak, soft (Moose hardness — 1), metallic luster and predominant ball shape. Sometimes the mineralization occurs as encrustations of hollows in aphyric amygdaloidal basalts, stockworks and small veinlets in the apical parts of basaltic lava flows. Manifestations of such rocks with Mn-mineralization are relatively common and encountered at each guyot.

The isotopic studies of carbomate veins (Isotopic Center, VSEGEI, SPb, Russia) with Mn-minerals point to hydrothermal origin with data coincided with carbonates of mid-ocean ridge basalts [6]:

δ13С (‰, PDB) 3.1, δ18O (‰, VSMOW) 32.1and are consistent with being a mixture of mantle carbon and carbon from a seawater. Low-temperature veins of calcite have δ13С values close to that of sea water and reflect the significant interaction of sea water with the basalts [5].

X-Ray analysis of the manganese oxide phase was carried out in the Crystallography Department of St. Petersburg University by V.B.Trofimov (DRON-9.0) and demonstrated the presence of lithiophorite (Al, Li) MnO2(OH)2.

Electron microprobe analysis was carried out the Institute of Precambrian Research (St. Petersburg, Russia) with Link-1000. It showed a high Mn/Fe ratio, the presence of Ni as an admixture. The high barium content can be explained by inclusion of barite crystals (less than 2—3 microns) in the area of the analуsing beam (3 microns). Native gold was identified in form of discrete grains. Comparison with analyses of hy-drogenous and hydrothermal manganese phase shows close affinity to hydrothermal manganese formations of the Mid-Ocean Ridge (MOR).

Despite the hydrothermal origin of calcite Mn-bearing veinlets, pneumatolitic way of formation is not excluded. The initial source of manganese could be a consequence of degassing mantle plumes [7] respon-sible for the formation of the Magellan Seamount chain.

These data demonstrate that guyots of the Pacific Ocean do not differ much from other oceanic forma-tion in manifestation of hydrothermal events and are able to make a significant contribution, in whole, to the manganese balance of the Ocean. Further studies of host (Mn-rich) tholeiitic basalts should be undertaken in order to evaluate the age, mantle-crust sources etc.

Estimates of the magmatic input of Mn should be carried out based on detailed studies of host basalts. Further mineralogical and chemical studies are planned to assess the sources and mechanisms of manganese transport.

46

Acknowledgments The author thanks Dr. M.Ye. Melnikov and Dr.V.M.Yubko for the opportunity to participate in the

cruises of SSE “Yuzhmorgeologia” and use samples for this research.

REFERENCESMelnikov, M.Ye.1. Deposits of Co-rich manganese crusts. Gelendzhik., SSC “Yuzhmorgeologia”, 2005, 230 (In Russian).Glasby,G.P.2. Manganese: Predominant Role of Nodules and Crusts. In: Schulz, H.D. and Zabel, M. (eds) Ma-rine Geochemistry. Springer-Verlag, Berlin, 2000, 335-372.Hein, J.R., Gibbs, A.E., Clague, D.A. and Torresan, M.3. Hydrothermal mineralization along submarine rift zones, Hawaiii. Mar.Georesourc. Geotechnol., 1996, 14: 177-203.Eckhard, J.D., Glasby, G.P., Puchelt, H. and Berner, Z.4. Hydrothermal manganese crusts from Enareta and Pa-linuro seamounts in the Tyrrhenian Sea, Marine Georesources. Geotechnol.,1997,15:175-209.Bogdanov Yu.A. et al. 5. Hydrothermal ore genesis of oceanic floor. Moscow, Nauka.2006. 527 p. (in Russian). Stakes D.S. и O.Neil J.R.6. Mineralogy and stable isotope geochemistry of hydrothermally altered oceanic rocks. Earth Planet. Sci.Lett, 1982, 57, 285-304.Rubin K.7. Degassing of metals and metalloids from erupting seamount and mid-ocean ridge volcanoes: obser-vations and predictions. Geochimica et Cosmochimica Acta, 1997, 61: 3525-3542.

47

METALLoGENIC PoTENTIAL oF oCEAN INTRAPLATE ENDoGENIC ACTIVITy

Valery М. Yubko

SSC «Yuzhmorgeologiya», Krymskaya Str.,20, Gelendzhik., 353461, Russia, e-mail: [email protected]

Except of widely-known manifestations of intraplate magmatism connected with activity of “hot-spots”, special type of magmatic activity was found at a number of oceanic floor areas at a depths of ca. 4000—6000 m. As a result, formation of rocks with specific geological age and setting takes place. Despite a wide distribution of such a formations (they were defined in a South Basin and northern subequatorial areas of the Pacific Ocean), certain similarity of their features is fixed.

Volcanites are characterized by specific petrochemical and geochemical peculiarities in all mentioned cases. These features are manifested in enrichment by alkalis (mostly by — К2О, and lithophilous elements). This fact sharply distinguish them from tholeiitic basalts of oceanic floor, but underlies affinity with basaltic products of intraplate volcanism, which is connected, as believed by many researchers, with a rather deep (100 and more km) magmatic sources.

Signatures of liquation (i.e. liquid immiscibility) differentiation in magmatic melts, which were defined long time ago, are not strange, and point to differentiation of magmatic melts resulted also in separation of their ore components (especially their sulfide components [1, 2]). In addition, other facts evidence to their ore generating activity and formation of hydrothermally- metasomatic sulfide ores in process of magmatic melts intrusion to sediments and effusion to a seafloor surface [3]. Possible scales and forms of manifestation of the mentioned rock types in the Ocean are considered by author.

REFERENCESProkoptzev, N.G.1. Atlas of deep-sea lavas of the Pacific Ocean. Moscow. Nauka., 1980, 142 p. (in Russian)..Prokoptzev, N.G2. . On mechanism of ore matter supply to oceanic floor from basaltic melt. “Doklady Akademii Nauk SSSR”, 1985, N4, pp. 964-968 (in Russian).Yubko V.M., Stoyanov , V.V., Gorelik, P.M3. . Geological structure and ore-bearing potential of Clarion-Clipper-ton Zone of the Pacific Ocean. Sovetskaya Geologya, 1990, N12. pp.72-80 (in Russian).

48

Section 2maSSive SulfideS

THe maP Of aBuNdaNCe Of Sulfide ORe iN THe OCeaN SCale 1:25 000 000

Andreev S.I., Anikeeva L.I., Kazakova V.E., Romanova L.I., Cherkashov G.A., Petukhov S.I., Sotnikova A.S., Mitina E.S., Lovchikova T.L., Ivanov N.K., Alekseev A.M.

VNIIOkeangeologia, Angliysky Prosp., 1, St. Petersburg, 190121, Russia, e – mail: [email protected]

The map was built on a temporal-structure material and geologotectonic basis reflecting a phase char-acter of development of the seabed. We separate four stages of the evolution — the Late Jurassic—Early Cretaceous (176—120 My) of non-regular spreading; the Cretaceous (120—80 My) characterized by seabed formation without evidences of spreading with widely-manifested superimposed volcanism; the Late Creta-ceous-Paleocene (80-26 My) of linear spreading; the Neocene-Quaternary (26—0 My) of linear spreading combined with the rise of oceanic seabed and formation of mid-oceanic ridges. At the first stage, early oce-anic plates built of primitive tholeiitic basalts were formed. Transitional non-spreading zone wherein the ba-salts evolve to sub-alkaline modifications was formed. During the third stage, later oceanic plates composed of basalts were founded; they had a tendency to a higher iron content. The fourth stage was marked by the formation of thalassides, the mid-oceanic rises, in the roof part of which a transition zone was founded with a hydrothermally active axial rift in the center. We distinguish three sections In the system of mid-oceanic ridges,. These are: the fast-spreading Indo-Pacific section (5—6 cm/year), the slower spreading Indo-Red Sea (5—6 cm/year) section and a slowly spreading Indo-Atlantic (< 3 cm/year) section.

In the ocean-to-continent transitional, zones we are fixing island arc rises, marginal and inner troughs joining them, active and passive rift zones, volcanoes. The main attention has been paid to the West Pacific transitional zone, which includes three sections: the Kuril-Aleutian (encialic), Japan-Marianna (encimatic and encialic), and Melanesian (mainly encimatic). The map of the ocean bed provides the data on the heat flow and contours of anomalous areas.

The metallogenic information includes data on the presence of deep-sea sulfide ores, direct indications of the presence of sulfide mineralization and indirect evidences of underwater hydrothermal activity (metal-liferous sediments, hydrothermal crusts, hydrothermal springs and gas sources).

Geochemical specialization of the massive and veined/impregnated sulfide ores has been defined using comparative coefficients obtained by dividing the particular value of Cu and Zn contents by mean values for these metals for the total Ocean. For Cu, this figure is 2.6%, for Zn — 7.8%. We may speak about 6 geo-chemical types of deep-sea sulfide ores:

— sulfur-pyrite with low content of Cu (<1%) and Zn (<2%);— copper-pyrite (Cu-Fe): Cu >1%, Zn <2%;— zinc-pyrite (Zn-Fe): Zn >2%, Cu <1%;— copper-zinc (Cu-Zn): Cu >1%, Zn >2%. Particular to mean quatient for Cu is higher than that for Zn.— copper-rich (Cu) chloride-hydrate atakamite ores are remarkable for high content of copper at neigh-

boring iron concentrations.Distribution of geochemical types of sulfide ores in the Ocean follows geodynamics of ore-controlling

structures, sections of middle ridges. The Cu-pyrite and Cu-Zn types prevail, the Cu-rich atakamite ones also encountered in the Indian Ocean. The Zn-pyrite and Zn-Cu types of ores are widely spread in the Indo-Pacific section. We meet Zn-Cu and Cu-Zn types of ore equally enriched in zinc and copper In the Indian-Red Sea section.

Geochemical types of ores various in composition were found in the West-Pacific transitional zone. They have Cu-Zn and of Zn-Cu specialization. The main specifity, though, of sulfide hydrothermal ore gen-esis in transitional zone is the occurrence of Pb among the leading ore components (the Jade and Sunrise ore

49

fields) in the part of Japan-Marianna Island arc system. It has an obvious or hypothetical encialic foundation (the Ryukyu arc and the Okinawa Trough, as well as the north of the Idzu-Bonino arc). From this point of view, one may also expect discoveries of sulfide ores with three leading metals Cu-Zn-Pb in the northward Kuril-Aleutian section founded on the sialic crust.

The indubitable fact of association of sulfide oceanic objects with the most energetic and geochemically active elements of divergent and convergent borders do not exclude discrete character of their occurrence and scattered locations on the seabed. At present we may separate 3 regions of concentration of deep-sea sulfide accumulations. Those are: three in the Mid-Atlantic section of middle ridges — the North-Atlantic Ridge (12°31’—40°00’N.), South-Atlantic and North-Indian Ridges. Three regions are located in the fast-spreading Indo-Pacific section — the Explorer ridge system, Endeavour, Juan de Fuca and Gorda, the north of the East-Pacific Rise, its southern part with an adjacent to the Galapagos region on the Galapagos fast-spreading ridge. Two regions, the Red Sea region and Central Indian one are located in the Indo-Red Sea section. The West-Pacific transitional zone includes three regions — Idzu-Bonino and Nansei (Ryukyu) island-arcs, Okinawa Trough, Marianna arc, Bismarck Sea (New Guiney) back-arc and the Solomon Sea, as well as Tonga-Kermadeck island arc.

Only half of these regions are located in the international waters — three in the Indo-Atlantic section, the North Atlantic and West-Indian ones; one in the Indo-Red Sea section, the Central Indian region; two in the Indo-Pacific section, the north and south of the East-Pacific Rise. Only one is of practical interest — the North Atlantic region containing nearly 40% of known deep-sea sulfides at a notable predominance of Cu over Zn. The region located in the southern part of the East-Pacific Rise is interesting for us, because these sulfide ores contain Cu. Recently, the Chinese geologists have significantly widened the resource base of the West-Indian section (the Last Chance field). Some ore objects have been found in the South Atlantic (Turtle Pits and Lilliput), where, according to heat flow data, one may expect some hints for the discovery of new sulfide manifestations.

International waters are known for its limited quantity of highly productive areas promising for deep-sea sulfides. However, one may find ways to expand their potential mainly thanks to two regions (the North-Atlantic and the South-Atlantic) in the borders of the slowly spreading section of MAR and, to some extent, of a weakly studied area at the south of the EPR in the Pacific and north of the triple junction Rodriguez in the Indian Ocean.

50

PHYSiCO-CHemiCal PaRameTeRS Of THe ORe-fORmiNG SYSTemS aT THe lOGaTCHev-1 HYdROTHeRmal field

(daTa ON fluid iNCluSiONS)

Bortnikov N.S.1, Simonov V.A.2, Shilova T.V.2, Fouquet Y.3

1Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, Staromonetnyi pereulok, 35, 119017, Moscow, Russia, e-mail: [email protected] of Geology and Mineralogy SB RAS, Academician Koptyug ave., 3, 630090, Novosibirsk, Russia, e-mail: [email protected], GM, BP70, 29280, Plouzane, Brest, France

Fluid inclusions in minerals of sulphide ore samples, selected during the French-Russian Serpentine cruise at the Logatchev-1 hydrothermal field (14°45’ N) in the Central Atlantic, were studied. Expedition was spent in 2007 on board the R/V Pourquoi Pas ? with use a ROV VICTOR. The major objective of the Ser-pentine cruise was to study the geological, geochemical and biological processes on the hydrothermal fields, associated with mantle derived ultramafic rocks (Fouquet et al., 2008).

Physico-chemical parameters of the ore-forming systems at the Logatchev-1 hydrothermal field have been defined by means of the analysis of fluid inclusions in anhydrite from samples DV-6-8 and DV-7-29. Inclusions were studied with the help of thermometry and cryometry methods (Ermakov, Dolgov, 1979; Roedder, 1984).

Primary fluid inclusions (5—60 microns) in anhydrite settle down in regular intervals and often occupy the central parts of anhydrite crystals. Inclusions have usually correct planar forms and contain two-phases: the transparent light liquid + an accurate round gas bubble. Presence of sulphide phases in inclusions testi-fies to capture by growing anhydrite an ore-forming fluid, from which simultaneously a crystallization of sulphide ore took place.

Experiments with fluid inclusions in the freezing stage have shown that solutions of inclusions in anhy-drite from the sample DV-7-29 are sharply frozen at temperatures -36.5— -40.5°C and have following eutec-tic temperatures: -25— -27°C. Thus, in the compositions of fluid inclusions solutions of NaCl is presented basically with KCl additive. Judging by melting temperatures of the last ice chips (-3.7— -4.8°C), one group with concentration of salts 5.8—7.6 wt. % is allocated. Cryometry researches of fluid inclusions in anhydrite of the sample DV-6-8 testify that solutions of inclusions freeze at temperatures -40.5— -41.0°C. During the heating the first portions of a liquid (eutectic) appear nearby -25— -28°C. Thus, in the compositions of in-clusion solution system NaCl-H2O dominate with additive KCl. Judging by prevailing melting temperatures of the last ice chips (-3.9— -5.2°C), salinity of the trapped solutions was 6.2—7.9 wt.% of NaCl equivalent. The values of concentration of salts for inclusions in anhydrite from samples DV-7-29 and DV-6-8 are very close among themselves and essentially above salinity of sea water (Fig. 1).

Experiments in the heating stage have allowed to define temperatures of homogenization of fluid inclu-sions for samples DV-7-29 and DV-6-8. According to thermometry of inclusions in anhydrite from the sam-

Fig. 1. Correlation of homogenization temperatures of fluid inclusions in anhydrite with contents of salts in their solutions.1—3 — the data on inclusions in anhydrite from Ashadze-1 hydrothermal field (1) and from samples DV-7-29 (2) and DV-6-8 (3) from Logatchev-1 hydro-thermal field. A black line — prevailing group of inclu-sions in anhydrite from Logatchev hydrothermal field (Simonov et al., 1997; Bortnikov, Simonov, Bogdanov, 2004). SW — salinity of sea water.

51

ple DV-7-29 three basic intervals of homogenization temperatures are established: 150—180°С, 190—220°С and 230—260°С. Taking into account correction for pressure, according to depth of sulphide ores location on the bottom of the ocean (nearby 3000 m), real temperatures of hydrothermal solutions have been esti-mated: 170—200°С, 210—240°С, 250—280°С. Thermometric researches of inclusions in anhydrite from the sample DV-6-8 testify to two intervals of homogenization temperatures: 190—240°С and 250—260°С. Taking into account the amendment on pressure, according to the depth of ocean in the sampling place (3000 m), intervals of temperatures of anhydrite crystallization constitute nearby 210—260°С and 270—280°С.

On the diagram showing correlation of homogenization temperatures of fluid inclusions in anhydrite with contents of salts in their solutions, it is clearly visible that the data on two studied samples is overlaped. It is possible to note only rather greater dispersion of temperature characteristics for inclusions from the sample DV-7 29 (Fig. 1). Absence of dependence of solutions concentration from temperatures can testify to an openness of hydrothermal system, as in case of the closed conditions at temperature decrease accordingly there would be also changes of concentration of solutions.

It was interesting to compare the received results to the information on the nearest hydrothermal fields at the Mid-Atlantic Ridge — Logatchev and Ashadze-1. Apparently on the diagram (Fig. 1) the data on fluid inclusions in anhydrite from sulphide ores from Logatchev and Ashadze-1 fields are close among themselves and considerably differ from inclusions from Logatchev-1 field, concerning decreased salinity and essential more high temperature. On the composition of solutions (basically NaCl with additive KCl) all these three fields coincide among themselves.

The considered fields are dated to the low-spreading Mid-Atlantic Ridge and naturally there is a necessity to compare to the data on high-spreading mid-oceanic ridges. Our information on fluid inclusions in anhydrite from sulphide ores of hydrothermal fields of the East Pacific Rise (Bortnikov et al., 2005) allows to make it.

During the comparative analysis the data of authors on fluid inclusions in anhydrite from sulphide ores of hydrothermal fields of the East Pacific Rise (EPR) was used: 9° N field (speed of spreading 10.6 sm/year) and 21°N field — rift valley of a mid-oceanic ridge with speed of spreading 6.2 sm/year. Is found out that com-positions of solutions at a hydrothermal field with the maximum speed of spreading (9° N EPR, NaCl with additive MgCl2) obviously differ from hydrothermal systems of Logatchev-1 field, where KCl is presented.

Salinity of solutions of Logatchev-1 is close to the data on 21° N EPR and it is essential below the con-tents of salts in hydrothermal solutions of 9° N EPR, reaching 13 wt.%.

Temperatures of hydrothermal solutions of Logatchev-1 field correspond to the data on rather low tem-perature inclusions in anhydrite of 21°N EPR field. In general for hydrothermal systems of high-spread-ing mid-oceanic ridges considerably more high temperatures (to 370°С), than established by us for the Logatchev-1 field, are characteristic.

As a whole, researches of fluid inclusions in anhydrite have shown that sulphide ores of the hydrothermal field Logatchev-1 were formed from the solutions with temperatures 170—280°С and salinity 4.5—9 wt.%. This contents of salts are above, than in hydrothermal systems of other fields at the low-spreading mid-oceanic ridges, but it is essential below the data on the hydrothermal solutions at the high-spreading ridges.

In the studied inclusions ore (sulphide) phases are situated, that directly testifies to equivalence of the fluid grasped by inclusions, to hydrothermal ore-forming solutions really operating at the Logatchev-1 field.

This work was supported by Federal Agency Rosnauka (State contract № 02.515.11.5083) and by Proj-ect №98.

RefeReNCeSBortnikov N.S., Simonov V.A., Bogdanov Yu.A.1. Fluid inclusions in minerals from modern sulphide constructions: physico-chemical conditions of mineral formation and fluid evolution // Geology of ore deposits. 2004. Т. 46. №1. P. 74-87. Bortnikov N.S., Simonov V.A., Dranichnikova V.V., Terenya E.O.2. Comparative analysis of physico-chemical param-eters of hydrothermal ore-forming systems in the low and high-spreading mid-ocean ridges: data on fluid inclu-sions in minerals // Russian – RIDGE. Abstracts volume. St. Petersburg: VNIIOkeangeologia. 2005. P. 14.Ermakov N.P., Dolgov Yu.A3. . Thermobarogeochemistry. M.: Nedra. 1979. 271 p. Fouquet Y., Cherkashev G., Charlou J.L., et al.4. Serpentine cruise – ultramafic hosted hydrothermal deposits on the Mid-Atlantic Ridge: First submersible studies on Ashadze 1 and 2, Logatchev 2 and Krasnov vent fields // Inter-Ridge News. 2008. V. 17. P. 15-19. Roedder E.5. Fluid inclusions // Mineral. Soc. Amer. 1984. 644 p. Simonov V.A., Lisitsyn A.P., Bogdanov Yu.A., Muraviev K.G6. . Physico-chemical conditions of modern hydrothermal ore-forming systems (black smokers) in the Central Atlantic // Geology of the seas and oceans. M. 1997. V. 2. P. 182.

52

maSSive Sulfide dePOSiTS aT SemYeNOv CluSTeR: miNeRalOGY, aGe aNd evOluTiON

Cherkashov Georgy2, Lazareva Larisa1, Stepanova Tamara2

1Polar Marine Geolodical Prospectin Expedition (PMGE), Pobedy St, 24, 188512, St.Petersburg, Lomonosov, Russia2VNIIOceangeologia, Angliysky Prosp., 1, St. Petersburg, 190121, Russia,

Seafloor massive sulfides (SMS) at cluster «Semyenov» is located at the western flank of the rift valley in the area of a seamount 13° 30' N, upon northern part of the flank terrace of the valley and limited from north by large non-transform fault of a third rank. Height of the mountain comprises 700 m, two volcanic edifices with access of 150 and 50 m are localized at the top. Deep rocks of upper mantle and crustal complexes were determined in the area. Manifestations of effusive rocks were represented by afiric and porfiric basalts, whereas plagiogranites were recovered at the northern slope. SMS cluster «Semyenov» is represented by five sites — “Semyenov-1” — “Semeyonov -5”.

Brief description of the hydrothermal fieldsSemyenov-1 is non-active, located at a depth interval of 2570—2620 m and associated with peridotites. It

is the sulfide mound with a size of 200×175 m. Pyrite and melnikovite-pyrite-marcasite SMS were determined, as well as copper chalcosite-chalcopyrite-isocubanite type in a lesser amount. Hydrothermal crusts were also recovered. Average contents of major elements (in %): Fe — 38.27, S — 39.1, Cu — 4.21, Zn — 0.22.

Semyenov-2 is basalt hosted field, within depths of 2370—2750 m. It consists of one ore body with a size of 600×400 m and another ore body with a size of 200×175 m. Two zones of hydrothermal activity with fauna were determined. It has complicated composition and represented by copper isocubanite-chalcopyrite ores with unstable quantity of covellite, chalcosite, bornite, as well as by copper-zinc sphalerite-chalcopyrite-opal ores. Ore- and ore-free breccias are widely spread, stockwerk-type ores in basalts and sulfidized opal and anhydride forms, and crusts are spread also. Average contents of major elements comprise (in %): Fe — 13.03, S — 19.77, Cu — 24.87, Zn — 4.2.

Semyenov-3 is related to both basalt and peridotite at a depths of 2400—600 m. It is inactive and has size of 1200—650 m. Ore formations are represented by pyrite-marcasite-opal breccias and massive pyrite and pyrite-marcasite ores. Apopyrite relics are typical for both types. Crusts were found, as well as rocks with veinlet-disseminated sulfide mineralization. Quantity of ore component comprises up to 90%. Average contents of major elements comprise (%): Fe — 39.32, S — 36.65, Cu — 0.22, Zn — 0.07.

Semyenov-4 is connected spatially with basalts. It is situated at a depths of 2580—2900 m, inactive and has a size of 2700×1600 m. It represents, probably, one of a largest agglomerations of SMS mounds within MAR. Pyrite, marcasite-pyrite ores with changable quantity of melnikovite and relics of pyrrhotite and iso-cubanite ores were identified. Copper- pyriteceous ores with isocubanite-chalcopyrite-pyrite composition are spread in a lesser amount. Sulfidized basalts and crusts with quartz were also met. Average contents of major elements comprise (in %): Fe — 41.83, S — 42.62, Cu — 1.20, Zn — 0.09.

Semyenov-5 is confined spatiallly to the field of basalt and peridotite at a depth of 2200—2500 m, has size of 700×500 m and inactive now. Copper-pyrite and pyrite-isocubanite-chalcopyrite ores with relics of pyrrhotite were identified, as well as pyrite, pyrite-marcasite types with unconstant quantity of melnikovite. Average content of major elements comprise (in %%): Fe — 39.55, S — 38.15, Cu — 10.61, Zn — 0.28.

Low-temperature and ore-free association of minerals is widely spread in all fields. It is represented by barite, aragonite, opal, quartz and anhydride (at the active field Semyenov-2). Macroscopic black and sooty secondary non-stoichiometric copper sulfides accompanying with copper, and copper-chalcopyrite ores.

The age of ore formationsThe results of uranium-thorium (Th/U) method of ore age determination are given in the scheme of

fig. 1. Range of age variations comprises 1,7 ± 0,4—123,8 ± 9,7/8,7 Ky.Generalized scheme of mineral formation sequence is suggested due to a high spatial variabilty of sulfide

ore composition, and variety of intensity of late processes manifestation — replacement of initial ore miner-als (pyrrhotite, isocubanite-chalcopyrite):

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1. Significantly more young marcasite, as well as pyrite-marcasite ores have age marks showed at fig. 1. These ores were formed possibly in two or three stages with often overlapping in space an earliest ores. Sig-nificantly older sphalerite and copper ores (represented by secondary and more late covellite-chalcosine covelline-barite have the age marks of 23,4, 24,7, 35,4 Ky.

2. Average meanings of mentioned age range are corresponding with pyrite-chalcopirite ores, ancient pyrite with chalcopyrite-isocubanite mineralisation, and with sometimes admixture of pyrrhotite and com-prise 50,3, 52,3 , 54,2, 64,6 , 72,2, 75,8, and 79,07,6 Ky. These ores were formed probably in two stages.

3. Apopyrrhotite ancient clusts in copper film with relics of ancient chalcopyrite, isocubanite are cor-responding with the age marks of 115,7 and 123,8 Ky. It is possible to suggest, that replacement and im-poverishment of ancient pyrrhotite ores (with relics of chalcopyrite, isocubanite) by chalcopyrite ores of various stages took place. Preservation of ancient ores in the eastern part of the ore cluster at the ore field Semyenov-4 can evidence to a lower intensity of late marcasite, marcasite-pyrite stages in the eastern part of the ore cluster.

Microprobe analysesAnomalously high concentrations of gold (26—188 ppm), silver (127—1788 ppm) were determined in

sulfide copper-zinc ores of ore field Semyonov-2, whereas high concentrations of selenium (470—1000 ppm) were determined in copper and copper-zinc ores.

Microprobe studies allowed to define phases of native gold, silver, as well as selenides of silver, gold and tellurides of silver.

Thin-dispersed gold was determined in copper-zinc tubes in their upper part of significantly opal com-position with admixture of secondary copper sulfides, aragonite, atakamite, iron-hydrooxides.

Thin-dispersed gold was discovered in ore breccias with cement of ore copper-zinc clusts and opal. Gold is confined to a sphalerite with high iron content and opal.

Phases of native gold were determined in massive copper-zinc ores of chalcopyrite-sphalerite-opal composition, Fig. 4.84, 4.85. Sizes of native gold particles are varying between 1 and 10 microns. Shape of particles is cloddy, dendrite-like and crescentiform.

Phases of native silver were determined in aragonite of opal-aragonite association which comprising copper-zinc tubes. Sizes are varying between 1 and 10 microns, shape of particles cloddy and dendrite-like.

Selenides of silver, gold were defined in massive and ball-shape opal in a massive ores of chalcopyrite-sphalerite-opal composition. Particles are localised not rarely in micropores, micro-cavities. Shape of par-ticles is dendrite, branching. Tellurides of silver were determined in sphalerite of ore breccias of copper-zinc composition, 4.91, 4.92. Size of particles is up to 3 microns, shape is cloddy.

It is possible to assume, that noble-metal mineralisation, as well as selenium-tellurium mineralisation were deposited in a final stage of a hydrothermal cycle with expanding oxidating conditions of mineral-forming environment, and at a geochemical barrier.

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NeW daTa ON THe lOW TemPeRaTuRe iRON dePOSiTS aT THe BROKeN SPuR aNd RaiNBOW HYdROTHeRmal veNT fieldS,

mid aTlaNTiC RidGe

Demina L.L., Bogdanova O.Yu., Novikov G.V., Galkin S.V.

Institute of oceanology of P.P.Shirshov of the Russian Academy of Sciences, 117997, Moscow, the Nahimovsky prospect, 36, the Russian Federation, e-mail: [email protected]

As a result of numerous expeditions of P.P. Shirshov Institute of oceanology of the Russian Academy of Sciences materials have been obtained almost from all basic active hydrothermal fields located in inner rift of the Mid Atlantic Ridge. Chemical and mineralogical composition of low-temperature deposits — crusts, touches, films covering different types of substrata at the Broken Spur and Rainbow hydrothermal vent fields were studied. In 2005 during cruise 50 of RV „Akademic Mstislav Keldish“ at these fields it was revealed such ochres covering surfaces of Bathymodiolus spp. mussel shells (Demina, Galkin, 2008). For the better under-standing of the nature of low-temperature hydrothermal deposits studies on mineralogy and geochemistry of the allocated films and crusts have been carried out.

The mineral structure of low-temperature phases of hydrothermal deposits was studied on an appearing through electronic microscope “JEM-100C”, equipped with goniometer (angle of slope ± 60°) and a power dispersive prefix “Kevex-1500”.

The chemical composition of deposits was determined by the atomic-absorption spectrometry with de-vices "KVANT-2А» (in a flame) and «КVANT-Z.ЭТА» (in graphite furnace), and by instrumental neutron activation analysis (measurement were done in the V.I. Vernadsky Institute of Geochemistry and analytical chemistry, Russian Academy of Sciences).

The Broken Spur hydrothermal field. Low-temperature deposits in the form of films were presented mainly by ferrous ochres substance consisting of ferrihydrite, having bacteria like forms, while getite was found in smaller quantities. The determined mineral structure was identical to structure of low-temperature hydrothermal deposits on the Wait Button chimneys at the Bogdanov site (Bogdanov, et al., 2008).

Content of Fe in the given deposits sharply prevails over content of Mn — 37.0 and 0.63 mas. %, accord-ingly. At the same time, the content of this elements is in limits, characteristic for low-temperature deposits of a hydrothermal field of Broken Spur: Fe — 33.1—44.8, Mn — 0.048—6.91 mas. %, accordingly (Bogdanov, et. al., 2008). Thus content of Mn in samples from Wait Button (6.91 mas. %) and Vasp Nest (0.048 mas. %) is one order higher and one order less one order in comparison with «shells materials». Average Fe/Mn ratio in these samples is 58.7. The trace metals average content in the samples are the following (ppm dry weight) : Ni — 390; Zn — 850; Co — 12.9; Cu — 22.65; Pb — 3.33; Cd — 1.00; Cr — 11,2; Se — 7.71; As — 204.1; Sb — 7.03; Hg — 0.15; Ag — 0.11; Au — 0.011. Comparison of these values with the content of microelements of the low-temperature deposits testifies a considerable (from 2.5 to ~750 (Cu) time) concentration in the latter. Another patttern was found for Ni2 , which is 1.5—4.5 times more in coverings of “shells” than in deposits. Such insig-nificant contents of the heavy and trace metals testify that chemical compound formation of Fe-hydroxydes took a place at a considerable distance from a hydrothermal vent inlets under their low concentration in water.

The Rainbow hydrothermal field. The surfaces of Bathymodiolus azoricus from 49 to 124 mm length is covered by crusts of low-temperature hydrothermal deposits with getite as a basic mineral. In certain samples ferrihydrite is widely developed. In samples with length of shells from 91 and 109 mm protoferrihydrite was found also. Except the above minerals small amounts of well enough crystallined hematite was present The similar mineral composition was determined as well for the low temperature ferrous deposits covering a sur-face of high-temperature hydrothermal sulphide deposits at the same field (Bogdanov, et al., 2004).

Content of Fe in samples of crusts varies from 29.7 to 48.5 mas. %, averaging 41.5 mas. %. Content of Mn changes from 0.0089 till 0.83 mas. %, at average value 0.28 mas. %. Average quantity of Fe/Mn ratio is ~150, in other words the crusts are enriched in Fe in comparison with Mn 2 orders of magnitude at least. A significant dependence between Fe and Mn content and a shell lengths was not observed.

Hence, it is possible to assume that accumulation of these ions of metals in crusts does not depend on time of exhibiting of organisms the waters enriched by iron, and is defined, most likely by a habitat of mus-sels. Content of Fe and Mn in low-temperature crusts of shells is in the same range of values, as for low- tem-perature the ferrous crusts covering a surface of high-temperature hydrothermal chimneys.

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The contents of trace metals in the low-temperature ferrous crusts varies in a wide range of values, an average (ppm) is the following: Ni — 98.0; Zn — 107.8; Co — 4.75; Cu — 37.5; Pb — 9.74; Cd — 0.73; Cr — 12.2; Se — 4.79; As — 110.3; Sb — 2.77; Hg — 0.26; Ag — 0.18; Au — 0.018. At the same time, the ferrous crusts covering a surface of hydrothermal chimneys are 2.35–125 times enriched in comparison with crusts of mussel shells, first of all — in Zn and Co. Besides, it is interesting to note that Ni2 content in the low-temperature ferrous deposits of mussel shells at the Broken Spur vent field is 4 times as much than in similar crusts of the Rainbow vent field.

The comparative analysis of mineral composition of all the investigated low-temperature ferrous de-posits of the Broken Spur and Rainbow fields has revealed their identity. Thus, getite, ferrihydrite, proto-ferrihydrite and hematite are typical ferrous phases of deposits of the given genesis. The identical mineral composition of all studied low-temperature deposits specifies that sedimentation of the Fe-hydroxides (with their subsequent transformation in hematite) is controlled by physical and chemical parameters of ocean water and does not depend on type of a substratum which carries out “a substrate” role. On the other hand, content of the ferrous minerals in samples is different. The increased content of Ni, Zn, As, Co, Se, Sb in Fe-hydroxides of Broken Spur field in comparison with at Rainbow field could be connected with the given parameter. On the opposute, higher content of Cu, Pb, Hg, Ag and Au was found in fer-rous deposits of the Rainbow vent field comparing to that of the Brocken Spur. Similar regularities have been revealed by us earlier for different types of ferromanganese deposits, including the low- temperature hydrothermal ferromanganese deposits (Novikov, Baturin, 1997; Novikov, Cherkashev, 2000; Novikov, Murdmaa, 2007; Novikov et al., 1995, 2006). From the content of trace metals in samples of the given hydrothermal fields, it is possible to assume that ferrihydrite shows the increased selectivity to ions of Ni, Zn and As, and getite – to ions of Cu, Pb and other metals. However it is impossible to exclude the other factor of enrichment of ferrous deposits, namely a various ways of input of trace metal ions into the Fe-hydroxides formation microzone during a local time intervals, or at the moment of their sorption by forming deposits.

Doubtless interest was represented by researches on distribution of ions of metals between low- temper-ature ferrous deposits, various tissues of shells and ocean water. The content of trace metals in Fe-hydroxides is 5—50 times more, than in the mussel soft tissues. Calculation of the ratio of the average content of trace metals (ppm dry weight) in ferrous deposits to that in mussel gills (Met.crusts/Met.gills) has shown the great-est enrichment in Fe (102) and Mn (104). To a lesser degree ferrous crusts are enriched comparing to gills in Ni (3,6), Sb (3,2), Se (3), As (2,2), Zn (2,8), Co (2); almost equal distribution shows Cr (1,4), while Cu (0,3), Hg (0,2) and Ag (0,1) show higher accumulation in mussel gills than in ferrous crusts.

Figure presents the measured concentrations of trace elements in the collected water samples from the Broken Spur and Rainbow vent fields and in a reference ocean water (Li, 1991) for comparison. The Bathy-modiolus spp. mussels inhabit areas influenced by the low-temperature diffusers (mussel habitats).

All the trace elements (besides Cr) are enriched 2-3 orders of magnitude relatively the reference ocean water. Cr showed the minimal enrichment (half order of magnitude) with respect to ocean water. The trace element concentrations are much higher in both the Broken Spur and Rainbow water samples compared to the reference ocean water. The water in biotope of Bathymodiolus spp. mussels at Rainbow vent field contains more Fe, Mn, Zn, Co, Cr, Ag, Pb, Se, Sb and Hg comparing to water samples collected in the Broken Spur mussel biotope. High content of Co is caused by influence of host ultramafic rocks. It is known that the low pH, the high temperature and high Cl-ion con-tent induce Cl complexes dominating fluid speciation, which results in the for-mation of aqueous metal chloride com-plexes (Douville et al., 2002). Trace ele-ments variability obviously is linked with their great affinity to form sulphide and Fe-Mn hydroxide precipitates, includ-ing possible precipitation in the sampler during collection.

The research was fulfilled with fi-nancial support of Grant of Funda-

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mental Scientific Schools NH-3714.2010.5. — “Study of the recent and ancient sedimentation in seas and oceans”, the Russian Foundation for Basic Research, project № 09-05-01050.

RefeReNCeSDemina L.L., Galkin S.V1. . About role of abiogenous factors in the heavy metals bioaccumulation in the hydro-thermal fauna of the Mid-Atlantic Ridge.//Oceanology. 2008. V.48. No 6. P.784-797.Bogdanov Yu.A, Lein A.Yu., Vikent2. ,ev I.V., Bogdanova O.Yu. et al. The low-temperature hydrothermal deposits of oceanic rifts genetic affinitied with serpentinites // New ideas in oceanology // Moscow: Nauka. 2004. V. 2. P. 372-402.Bogdanov Yu.A., Vikent3. ,ev I.V., Lein A.Yu., Bogdanova O.Yu. et al. The low-temperature hydrothermal deposits of rift zone of the Mid-Atlantic Ridge // Geology ore deposits. 2008. V. 50. № 2. P. 135-152. Novikov G.V., Baturin G.N.4. Sorption ability of oceanic and marine ferromanganese nodules and crusts of dif-ferent chemical and mineralogical composition // Oceanology. 1997. V. 37. № 4. P. 472-478.Novikov G.V., Cherkashev G.A5. . Ion-exchange reactions on low-temperature oceanic hydrothermal rocks // Geochemistry International. 2000. V. 38. Suppl. 2. P. 194-205.Novikov G.V., Murdmaa I.O.6. Ion exchange properties of oceanic ferromanganese nodules and enclosing pe-lagic sediments // Litology and mineral resources. 2007. V. 42. № 2. P. 137-167.Novikov G.V., Andreev S.I., Anikeeva L.I.7. Sorbtionic activity of oceanic ferromanganese deposits // SPb.: VNIIOceangeology. 1995. V. 2. P. 291-304.Novikov G.V., Vikent8. ,ev I.V., Bogdanova O.Yu. Sorption of heavy metal cations by low-temperature deposits of Pacific hydrothermal fields // Geology of ore deposits. 2006. V. 48. № 4. P.304-325. Douville E., Charlou J.L., Oelkers E.H., et al9. . The Rainbow vent fluids (36o14’N, MAR): the influence of ul-tramaphic rocks and phase separation on trace metals content in Mid-Atlantic Ridge hydrothermal fluids // Chemical Geology. 2002. V.184. No 1. P.37-48.Li Y.H.10. Distribution patterns of the elements in the ocean: a synthesis// Geochim. Cosmochim. Acta. 1991. V. 55. P.3223-3240.

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HYdROTHeRmal miNeRal-GeOCHemiCal ZONaTiON iN THe SedimeNTS Of THe aSHadZe-1 HYdROTHeRmal field

(maR, 13°N)

Gablina I.F.1, Popova E.A.2, Sadchikova T.A.1, Beltenyov V.Ye.3, Shilov V.V. 3

1Geological Institute RAS, Pyzhevsky per. 7, 119017, Moscow, Russia, e-mail: [email protected], 2VNIIOkeangeologia, Anglyisky Prosp.1, 190121, St.Petersburg, Russia, e-mail: [email protected] Polar Marine Geolodical Prospectin Expedition, Pobedy St, 24, 188512, St.Petersburg, Lomonosov, Russia, e-mail: [email protected]

The study of alterations in sediments in connection with recent hydrothermal activity is important both for better understanding of processes of mineral and ore formation at the ocean floor and for practical purpose: to reveal zones enriched in metals. Sulfide ores of hydrothermal constructions are desintegrating right after their deposition, under the influence of surrounding seawater, which causes their appreciable depletion. However, the long-lasting influence of metalliferous fluids on the sediments, particularly regard-ing their considerable thickness, which rule out the effect of supergene factors, might bring to the formation and preservation of great accumulations of useful components. Studying the recent hydrothermal mineral formation in sediments, we are getting knowledge about initial stages of deposits development.

In this paper, the attention is focused on new mineral formations in bottom sediments of the recent Ashadze-1 hydrothermal field of MAR, directly in the zone of hydrotherms exposure and at variable distance from it. To de-termine the nature of mineral components, organic substance of sediments was selected for investigation; at the sedimentation stage, its composition is uniform all over the ocean: it consists of calcite shells of died out plankton and benthos. Differences in their transformation may be only due to different conditions of diagenesis.

The Ashadze field situated at a depth of 4100—4200 m, extends in the EW direction; its area is 450 x 350 m. The field lies near the base of the western slope of the rift valley in the high-activity area, where the boundary deep-seated fault crosses the zone of sublatitudinal tectonic deformations. The geological struc-ture of the field consists of gabbroids and serpentinized peridotites overlain by recent biogenic carbonate and clay-carbonate foraminiferal coccolite sediments with fragments of altered substrate rocks occurring in lower horizons. The sediments are more than 3 m thick, and closer to hydrothermal constructions their thickness decreases to 0.5 m and less. The ore field is represented by two ore bodies with relict and active hydrothermal constructions and ore-bearing sediments. Water bottom layers show anomalous values of turbidity, tempera-ture, and of the content of dissolved Fe and Mn, as well as a declined density of bottom waters due to great amounts of gases, in particular hydrogen and methane, in hydrotherms [1, 4]. The temperature of solutions at that field reaches 353°C, pH from 3.5, and the mineralization from 0.8 to 1.3 of the sea water salinity [3]. The age of sediments dated by the fauna assemblage is the Holocene-Upper Pleistocene (0—30 ka) [5].

Specialists from VNIIOkeangeologia selected the samples studied from columns of Sts. 1508, 1509, 1518, 520, 1519, and 1521 by the telegreifer along the sublatitudinal profile during the 26th leg of the R/V “Professor Logachev”, which was conducted by the Federal State Unitary Enterprise (FSUE) “Polar Expe-dition” (PMGPE) in 2005. Sediments were recovered at a depth of 5 to 60 cm. Samples of background sedi-ments, recovered at approximately 1 km north (St. 1515) and 1—2 km south (St. 1430, 1525) of the center of the ore field, were compared with the ore-bearing and metalliferous samples. The particle-size, chemical, optical, X-ray, electron microscopy analyses, and RSMA were applied.

The chemical analysis conducted at VNIIOkeangeologiya on material of all the stations of the ore field, has revealed the zonal distribution of rock-forming and ore elements: from the ore field periphery towards its center (to ore bodies), the carbonate and Mn, Mg, Corg content in sediments 10-fold declines, while the content of Fe, Si, and Cu sharply increases. The zonal distribution of elements is most clearly distinguished in Horizon 2 (2—20 cm) (Fig. 1). Ore bodies in sediments are characterized by high Fe (10-30% or more) and Cu (more than 5%) content. The western flank of ore body 1 (St. 1508) exhibits a zone of anomalously high Mg content (to 10—22% MgO), and ore body 2 is bordered in the north by a Mn-rich zone.

The zonal distribution of chemical elements in sediments is specified by their mineral composition. The X-ray analysis suggested that the dominating clay mineral in the sediments of the hydrothermal field and beyond it is kaolinite. With one exception: the sediments of St. 1508, located in a raised magnesium zone. Most abun-dant here is Fe-smectite with Mg and Ca between beds. The same cation composition of smectite prevails in the

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Fig. 1. Fe (a), Cu (b), and Mg (c) Distribution in Horizon 2 (2—20 cm) of Sediments of the Ashadze-1 Field (converted to noncarbonated matter)

samples, where it appears as an admixture mineral, except for St. 1521, situated at the northeast margin of the ore field, which is most distant from ore deposits, and Sts. 1515, 1430, 1525, situated outside of the ore field. Here kaolinite is also predominant, and smectite is represented by its variety with K and Na between beds.

The chemical zonation reflects mineralization features of foraminiferal shells, which in ore bodies were completely were substituted by hydrothermal minerals. By the composition of dominant minerals, which cover and replace shells, the following zones are identified in the sediments of the Ashadze-1 field: 1) sul-

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fide, coinciding with ore bodies; 2) zone of elevated magnesium content at the ore body 1 western flank, and 3) a zone of developing Fe-Mn crust rimming ore bodies 1 and 2. At periphery of the hydrothermal field, processes of dissolution and replacement of carbonate shells by secondary minerals attenuate. In the sulfide zone and the zone with elevated magnesium content, secondary minerals, which replace carbonate shells, are represented by sulfides: variably oxidized pyrite, Fe and Cu sulfides; by silicates: tremolite-actinolite, ser-pentine, Fe-Mg-smectites, saponite (?), probably, palygorskite (sepiolite); by carbonates: Mg-Mn-bearing siderite; by oxides: Fe oxi-hydroxides, frequently mixed with SiO2. Analogous new-formed minerals make up the crustified and porous cement of sediments. In addition the crustified cement contains isolated crystals of barite, quartz, calcite, celestine, gypsum, and anhydrite. Coating of carbonaceous substance is recorded on shells throughout the section (of columns).

Pyrite and siderite are most widespread new-generated minerals in the studied columns of ore sedi-ments. Pyrite is oxidized in varying degrees and contains inclusions of copper and copper-iron sulfides. When forams are replaced by pyrite undergoing subsequent crystallization and oxidation, the primary fea-tures of shells completely disappears. The majority of new-formed non-ore minerals have a high Mg content. Siderite comprises appreciable amounts of Mg and Mn. Thin-crystalline siderite, which replaces calcite shells, is characterized by a higher Mg (9.55—11.36%, on the average 10.39%) and Mn (6.07—7.21, on the average 6.19) content as compared with the later siderite of cement. In the latter the Mg content varies from 0.84 to 10.9%, being on the average 7.42%, and Mn, from 3.25 to 6.78%, on the average 4.96%.

The mineral-geochemical zonation, identified in sediments of the Ashadze-1 field, is associated with the superimposed hydrothermal processes, which led to substantial reworking of organic sedimentary material. Being affected by acid reducing hydrothermal fluids, which penetrated through the sediments, calcite shells of foraminifers were metasomatically (developing pseudomorphs) substituted by pyrite, sulfides of copper, copper-iron, by siderite, serpentine, and other hydrothermal minerals. Consequently, ore bodies generated in the sediments were rich in copper and iron. Of particular interest is the presence of high magnesium zone in the sediments of the Ashadze-1 field, which makes it prominent among other hydrothermal fields of the Atlantic region. It is well-known that Mg-bearing silicates in association with sulfides, silica, and anhydrite mark areas of hydrothermal discharge in the Red Sea [2]. It is significant that Mg is also recorded in hydro-therms of the Red Sea, though it is not at all typical of oceanic hydrothermal sources. Usually, oceanic hy-drotherms are devoid of Mg. Wide development of Mg-rich minerals in hydrothermally-altered ore-bearing sediments in the Ashadze-1 field indicates a high content of this element in fluids, affecting sediments. The identified Mg-elevated zone in the Ashadze-1 field suggests the existence of autonomous source of hydro-thermal fluids, shifted westward as related to the main ore-forming zone (orebodies) (see Fig. 1), and being different in composition and physical-chemical properties of fluids. The quantitative ratio of Fe, Mg, and Mn in the composition of hydrothermal siderite of different generations reflects a progressive decrease of Mg and Mn content in mineral-forming solutions.

The work was supported by the Russian Foundation for Basic Research (project no.08-05-00499). The leg of the R/V “Professor Logatchev” was organized by PMGPE and sponsored by the Federal Agency for Nature Management of the Ministry for Natural Resources.

RefeReNCeSBel’tenev V.E., Stepanova T.V., Shilov V.V., et al. New Hydrothermal Field, 12°58,4’ N and 44°51,8’ W MAR 1. // Processes in Spreading and Ultraspreading Oceanic Ridges: from mantle Melting to Biota in Hydrothermal Sources. The Working Conference of the Russian Department of the International Interridge Project. Mos-cow, Vernadskii Institute of Geochemistry and Analytical Chemistry (GEOKHI), 2003, p. 15.Butuzova G.Yu. Hydrothermal-Sedimentary Ore Formation in the Rift Zone of theRed Sea. Transactions of 2. GIN RAS, Issue 508, Moscow: GEOS. 1998. 311 p.Sudarikov S.M., Kaminskii D.V., Krivitskaya, et al. Hydrothermal Fluids and Plumes of the Segment 13°-3. 16°N of the Mid-Atlantic Ridge. // National Resources of the World Ocean-4. Materials of the International Conference. St.Petersburg. VNIIOkeangeologia. 2008. p.92-93.Sudarikov S.M., Kaminskii D.V., Narkevskii E.V. Hydrophysical and Hydrochemical Features of Hydrother-4. mal Plumes in Bottom Waters of the Region 12°58’ N MAR. The VI Working Conference of the Russian De-partment of the International InterRidge Project, June 6-7, 2009. St.Petersburg. VNIIOkeangeologia. 2009. pp. 55-57. Shilov V.V., Cherkashev G.A., Kuznetsov V.Yu., et al. Initial Data on High-Temperature Hydrothermal Activ-5. ity, with the Age of More than 200 ka(MAR, Area 13° N). // Working Conference of the Russian Division of the International InterRidge Project, St.Petersburg, 2005, p. 4.

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SemeNOv HYdROTHeRmal NOde (13031’ N, mid-aTlaNTiC RidGe): RadiOCHemiCal STudY, 230TH/u daTiNG aNd CHRONOlOGY Of ORe fORmaTiON

Kuznetsov V.1, Cherkashov G.2, Bel’tenev V.3, Lazareva L.3, Maksimov F.1, Zheleznov A.1, Baranova N.1, Zherebtsov I.1

1St. Petersburg State University, V.O., 10-th Line 33, 199178, St. Petersburg, Russia e-mail: [email protected] for Geology and Mineral Resources of the Ocean (VNIIOkeangeologia) Angliysky Prospect 1, 190121, St. Petersburg, Russia3Polar Marine Geosurvey Expedition, Pobedy Str. 24, 198412 Lomonosov, St. Petersburg, Russia

The chronology of hydrothermal activity stages and ore-forming processes caused by it during last about 250 ka can be restored applying the 230Th/U dating of sulfide ores deposited within the Mid Oceanic Ridges. The temporal evolution and duration of hydrothermal activity stages determined also by means of 14C and 230Th dates of metalliferous sediments from different hydrothermal fields (Cherkashev, 1995; Kuznetsov, 2008). It was established that hydrothermal events have pulse-type mode in time (Lalou et al., 1995; 1998; You and Bickle, 1998; Kuznetsov et al., 2007). But there is still a small number of dates to get a general view on the frequency and duration of hydrothermal events in the world as a whole and within hydrothermal fields at the Mid-Atlantic Ridge (MAR) particularly. Besides, compositional peculiarities of hydrothermal depos-its and features of its origin requires special experimental checking of main theoretical positions of 230Th/U dating method to obtain the reliable age data for each hydrothermal field under study.

The main objectives of this study were: — to check whether reliable 230Th/U dates can be determined from oceanic sulfide ores; — to determine first numerical dates from recently discovered Semenov hydrothermal node at the MAR.The Semenov ore node was discovered in 2007 during the cruise of Russian R/V “Professor Logatchev”

had been organized by Polar Marine Geosurvey Expedition (PMGE, St. Petersburg) and VNIIOkeangeolo-gia (St. Petersburg). The node is located on the western scarp of a rift valley. It includes the West, North-West, North-East and East hydrothermal fields. The structure with which fields are connected is the underwater mountain. It towers over the terrace surface on 850 m and is extended in latitudinal direction approximately on 10 km with about 4,5 km width (Beltenev et al., 2007; 2009).

Sampling was carried out by means of dredging and TV-controlled grab system within the hydrothermal sites.The 230Th/U dating method for massive sulfides is based on the disturbance of the radioactive equilib-

rium between mother and daughter isotopes of the natural 238U decay series in ocean and correspondingly in hydrothermal deposits. The growth of 230Th from 234U gives the chance to determine age of sulfide ores and the present 230Th/234U activity ratios (AR) is the measure of sample age.

There are two main prerequisites for 230Th/U dating of oceanic sulfides ores (Lalou and Brichet, 1987; Lalou et al., 1996; Kuznetsov et al., 2002, 2006; Kuznetsov, 2008):

1. Just deposited sulfides contain uranium but no thorium.2. The sulfides behaved under chemically closed conditions during aging with regard to uranium and thorium.We carried out detailed radiochemical studies of ore formations from both the Semenov node (MAR)

and the 9°50’ N hydrothermal field within the East Pacific Rise (EPR) to check the first position of 230Th/U method. It was established by different researches that small-sized build-ups in the area of 9°50’ N (EPR) have been forming during last about 20 years after the volcanic event in 1991 (Bogdanov et al., 2006). The radiochemical analyses to determine the contents of 230Th, 232Th, 234U and 238U in the ore samples were carried out. We obtained that the specific activities of both thorium isotopes were below the detection limit whereas the specific activities of both uranium isotopes were in measurable content in the range of 0.2—0.7 dpm/g. We have obtained also the specific activity of 232Th was either negligible or below the detection limit in all studied sulfide ore samples from the Semenov node (MAR). It is evidence that terrigenous matter containing 238U, 234U, 232Th, 230Th is actually absent in the samples. Thus, it is possible to conclude that the 230Th is purely radiogenic and formed by decay of its parent radionuclides 234U and 238U of the sulfide ores.

The data on contents and distribution of the 238U, 234U, 232Th, 230Th isotopes and their activity ratios in the studied sulfide formations from the Semenov node allowed us to conclude that increase or decrease of uranium activity does not influence on age of samples. According to Lalou et al. (1996), the absence of a systematic relationship between the uranium activity and the sample age from the same hydrothermal field

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gives evidence that closed-system conditions with respect to U (preventing addition or leaching) prevailed in the sulfide — sea water system. Noteworthy, the fact of no thorium isotope migration in different types of oceanic deposits has been proved by many investigations (Kuznetsov, 1976; Kuznetsov and Andreev, 1995; Huh and Ku, 1984; Lalou et al., 1988), therefore, we believe that there is no reasons for possible migration of thorium (primarily 230Th) in the solid phase of sulfide formations together with pore water. Thus, complying with the second requirement of the 230Th/U method seems justified and the application of the 230Th/U dat-ing of the sulfide deposits studied may well be justified.

The dating results can be used in various purposes. First, we determined the total age range no less than ~124 ka for sulfide deposits corresponding to the beginning of ore formation within the node as a whole. Sec-ond, the hydrothermal activity started here no earlier than ~37, ~76, ~90 and ~124 ka ago for the West, North-West, North-East and West hydrothermal fields, correspondingly. Third, the hydrothermal activity started in the eastern part of the Semenov node and moved to the west keeping the stages of ore-forming. Fourth, we can tentatively recognize the temporal stages of hydrothermal activity development within the each field: no less 4—5 episodes for the West, North-West and North-East field and about 12 episodes for the East field.

The work was supported by the Russian Foundation of Basic Research, grant No. 08-05-00919. We thank to PMGE, VNIIOkeangeologia and SIO RAN for providing the samples of hydrothermal

sulfide deposits for this study.

RefeReNCeS.Cherkasev G.A. 1. Hydrothermal input into sediments of the Mid-Atlantic Ridge // Parsson L.M., Walker C.L. and Dixon D.R. (eds.) Hydrothermal Vents and Processes. Geological Society London, Special Publication. 1995. V. 87. P. 223-229. Kuznetsov V.Yu.2. Radiochronology of Quaternary deposits. Saint-Petersburg. 2008. 312 p. (in Russian).Lalou C., Reyss J.-L., Brichet E., Rona P.A., and Thompson G.3. Hydrothermal activity on a 105-year scale at a slow-spreading ridge. TAG hydrothermal field, Mid-Atlantic Ridge 260N // J. Geophys. Res. 1995. V. 100. P. 17855-17862. Lalou C., Reyss J.-L., Brichet E.4. Age of sub-bottom sulfide samples at the TAG active mound // Herzig P.M., Humphris S.E., Miller D.J., and Zierenberg R.A. (Eds). Proceedings of the Ocean Drilling Program, Scien-tific Results. 1998. V. 158. P. 111-117.You C.-F. and Bickle M5. . Evolution of an active sea-floor massive sulphide deposit // Nature. 1998. V. 394. P. 668-671.Kuznetsov V.Yu., Cherkashev G.A., Bel’tenev V.E., Lein A.Yu., Maximov F.E., Shilov V.V., Stepanova T.V. 6. The 230Th/U Dating of Sulfide Ores in the Ocean: Methodical Possibilities, Measurement Results and Perspectives of Application // Doklady Earth Sciences. 2007. V. 417, N 8. P. 1202-1205. Beltenev V., Ivanov V., Rozhdestvenskaya I., Cherkashov G.,7. Stepanova T., Shilov V., Pertsev A., Davydov M.,

Egorov I., Melekestseva I., Narkevsky E., Ignatov V. A new hydrothermal field at l3° 30’ N on the Mid-Atlantic Ridge // InterRidge News. 2007. V. 16. P. 9-10.Beltenev V., Ivanov V., Rozhdestvenskaya I., Cherkashov G., Stepanova T., Shilov V., Davydov M., Laiba A., 8. Kaylio V., Narkevsky E., Pertsev A., Dobretzova I., Gustaytis A., Popova Ye., Amplieva Ye., and Evrard C. New data about hydrothermal fields on the Mid-Atlantic Ridge between 11° - 14° N: 32nd Cruise of R/V Professor Logatchev // InterRidge News. 2009. V. 18. P. 14-18. Lalou C., Brichet E.9. On the isotopic chronology of submarine hydrothermal deposits // Chem. Geol. 1987. V. 65. P. 197-207. Lalou C., Reyss J.L., Brichet E., Krasnov S., Stepanova T., Cherkashev G. and Markov V.10. Initial chronology of a recently discovered hydrothermal field at 14°45’N, Mid-Atlantic Ridge // Earth and Planetary Science Let-ters. 1996. V. 144. P. 483-490.Kuznetsov V.Yu., Arslanov Kh.A., Shilov V.V., Cherkashev G. A11. . 230Th-excess and 14C dating of pelagic sedi-ments from the hydrothermal zone of the North Atlantic // Geochronometria. 2002. V. 21. P. 33-40. Kuznetsov V., Cherkashev G., Lein A., Shilov V., Maksimov F., Arslanov Kh., Stepanova T., Baranova N., Cher-12. nov S., Tarasenko D. 230Th/U dating of massive sulfides from the Logatchev and Rainbow hydrothermal fields (Mid-Atlantic Ridge) // Geochronometria. 2006. V. 25. P. 51-56. Bogdanov Yu.A., Lein A.Yu., Ulyanov A.A., Maslennikov V.V., Ulyanova N.V., Sagalevich A.M.13. Initial stage of ore ac-cumulation in the 9050’ field at the East Pacific Rise // Okeanologia. 2006. V. 46, N. 1. P. 88-102 (in Russian).Kuznetsov Yu.V.14. Radiochronology of Ocean. 1976. Atomizdat, Moscow. 279 p. (in Russian).Kuznetsov V.Yu., Andreev S.I.15. Distribution of uranium and thorium isotopes in ferromanganese nodules from the Pacific Ocean // Radiochemistry. 1995. V. 37. N. 4. P. 346-351.Huh C.A., Ku T.L.16. Radiochemical observation on manganese nodules from three sedimentary environments in the North Pacific // Geochimica et Cosmochimica Acta. 1984. V. 48, N. 5. P. 951-963.Lalou C., Reyss L.G., Brichet E., Krasnov S., Stepanova T., Cherkashev G., Markov V17. . Chronology of a recently discovered hydrothermal field at 14°45’ N, Mid Atlantic Ridge // Earth and Planetary Science Letters. 1988. V. 144. P. 483-490.

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KiNeTiCS aNd equiliBRia aT mixiNG Of fluidS: exPeRimeNTal aNd COmPuTed daTa

Laptev Yu., Novikova S.

Institute of Geology and Mineralogy SB RAS, Ac. Koptyug Av. 3, 630090, Novosibirsk, Russia, e-mail: [email protected]

Experimental and thermodynamic study of the formation conditions of sulfates and sulfides with gold participation at mixing of fluids has been carried out as this geochemical process is important in the condi-tions of modern and ancient sulfide formation. Experimental procedure was based on the interaction of the components by the following scheme MeCl2 + H2S (H2SO4) → MeS (MeSO4) + 2HCl immediately at the high temperature. The first results on the synthesis of barite BaSO4, sphalerite (Zn, Fe)S and pyrite FeS2 in the presence of dissolved Au at t = 250°C, P = 100 bar were obtained. Precipitation of micro amounts of gold from Au-containing weakly acid sulfide solution (0.1 m H2S, pH = 6.3) occurred automatically due to the increase of solutions acidity during the main process of sulfides formation (up to pH = 2). Experimental data on the composition of fluid and solid phases were correlated with computer calculations made by HCh com-puter program. Calculation module was first used to determine sphalerite composition (solid solution ZnS-FeS) by Margulis asymmetric model. Mole fraction of FeS in the sphalerite (XFeS) was used as sulfur fugacity indicator for its associations with pyrite in the presence of barite (1), magnetite (2) and pyrrhotite (3).

Fig. 1. SEM for the barite samples, synthesized at room temperature (a) and at 250°C (b).

Fig. 2. SEM for the sphalerite samples, synthesized at room temperature (a) and 250°C (b).

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According to the XRD, SEM, and EXAFS data it is found that only the adopted procedure of the high temperature mixing of the components (relative to the synthesis of the same phases at room temperature) provides the formation of ideal crystal structure of the newly formed phases. The degree of super saturation of the solutions, which was defined by the rate of solid phases formation (from 400 to 35 mg of the solid phase in 1 liter of solution per 1 min), was not the controlling factor in the morphology and crystallinity of the newly formed products.

Temperature increase of barite synthesis from room to 250°C causes the increase of the crystal size from 1 to 10 µm (Fig. 1). In this case, tabular crystals transform into the crystals with pseudo cubic morphology and inner cavities. Sphalerite particles grow in the same manner (from 1 to 5 µm) with characteristic for-mation of its nodular aggregations at 250°C (Fig. 2). Pyrite synthesis doesn’t cause the formation of easily observable crystals (<1 µm). Marcasite forms together with pyrite. Gold concentration in the sphalerite and pyrite mixture (with gold content of the first percents) is followed by the formation of metal Au phase (XRD data) visible under a electron microscope (SEM data). EXAFS spectra support this fact and show minimal size of gold micro particles of about 30 nm.

Data on the compositions of the solutions and solid phases correspond to the results of computer mod-eling. Mole fraction of FeS in the sphalerite at the joint pyrite, sphalerite and barite formation didn’t exceed the value 0.03. According to the computer modeling it must rise up to 0.11 in the sphalerite association with pyrite and magnetite. XFeS is 0.23 in sphalerite, pyrite and pyrrhotite association. This is in good agreement with the experimental data on this equilibrium in the “dry” systems (Barton, Toulmin, Skinner, Lusk et al.). The formation of sphalerite with low iron content together with pyrite and barite as typical Zn-polymetallic association is a regular consequence of the highest sulfur fugacity during hydrothermal sulfide formation by the mixing of fluids with difference red-ox properties.

Grant RFBR 09-05-00862

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meSOZOiC BlaCK SmOKeRS iN PONTideS iNTRa aRC BaSiN Of THe TeTHYS PalaeOOCeaN

Maslennikov V.V., Maslennikova S.P.

Institute of Mineralogy, Ural Division, Russian Academy of Sciences, 456317 Miass, Russia, e-mail: [email protected]

The discovery of ancient black smokers in volcanogenic massive sulfide deposits (VHMS) is not ordinary adventure (Scott, 1981). Some deposits of the Palaeozoic Urals and Rudnyi Altai, and also Cenozoic Hokuroko massive sulfide deposits have yielded a number of very well-preserved sulfide vent chimneys (Shikazono and Kusakabe, 1999; Herrington et al., 1998; Little at al., 1997; Maslennikova, Maslennikov, 2007; Maslennikov et al., 2009). The findings of Mesozoic chimneys are less known.

The rare occurrences of Mesozoic black smoker chimneys are known in volcanogenic massive sulfide deposits of Cyprus (Oudin and Constantinou, 1984) and California (Little et al., 1999). The deposits are located on basalt basement of back arc basins. The chimney fragments have a chalcopyrite-pyrite composition and simple zonation. Outer walls of some chimneys are mantled by colloform pyrite, and the axial conduits are filled with crystalline chalcopyrite. The chimneys lack of any rare minerals and were not chemically studied.

Last year, we found a variety of very well-preserved fossil vent chimneys in the Cretaceous VHMS deposits in the Pontides intra arc basin of Tethys Palaeocean. The deposits are located into bimodal felsic units where dacite and rhyolite are dominant rocks. Ore bodies generally point to a continuum in degradation and re-working range from pristine steep-sided hydrothermal sulfide mounds (Kutlular and Caely-Madenkoy) to those deposits dominated by layered strata of clastic sulfides (Lahanos, Killik, Kisilkaya). The chimney frag-ments reside in coarse sulfide breccias. In the VHMS deposits, the chimneys are accompanied by tube worms which could presumably be counterparts of modern near vent vestimentiferans. Sulfide mounds and clastic sulfides underwent seafloor and sub seafloor supergene alteration with successive replacement of colloform pyrite by chalcopyrite, bornite, fahlore, and hematite.

The chimneys are ranged from chalcopyrite-pyrite, chalcopyrite-sphalerite-pyrite to barite-sphalerite-chalcopyrite varieties. In general, the mineralogical zonation shown by various ancient chimneys is broadly comparable with those studied in modern black or gray smoker chimneys, with the exception of the lack of evidence for the former initial chimney shell of anhydrite or silica and pyrrhotite crystals. Pyrite in the outer walls (zone A) is primarily colloform. In the inner parts of outer walls of the chimneys, the colloform and fine pyrite were partly replaced by marcasite and euhedral pyrite in association with sphalerite and chalcopyrite. The chimneys with sphalerite-rich outer wall were found as well. The inner walls (zone B) of the chimneys were always formed by coarse subhedral chalcopyrite. The axial conduit zones (zone C) of some chimneys were consequently filled with sphalerite, pyrite, marcasite quartz and/or barite. The mineralogical zonation may be interpreted in terms of zoned formation temperatures and redox conditions across the chimney wall during seafloor hydrothermal precipitation.

Chalcopyrite-rich chimneys (Lahanos, Kutlular) show fine inclusions of tellurium-bearing phases, such as tellurobismuthite and hessite. In sphalerite-rich chimneys, galena and fahlores are widespread. The gold inclusions occur in chalcopyrite in association with bornite. Some sphalerite-filled conduits contain inclu-sion of gold in association with galena and fahlores (e.g. in Caely-Madenkoy in Zaykov et al., 2005). The oc-currence of tellurides suggests resemblances of the chimneys with those discovered in the Paleozoic VHMS deposits of the Urals ensimatic island arcs [Herrington et al., 1998; Maslennikova, Maslennikov, 2007; Maslennikov et al., 2009] and also in some modern black smokers at MOR (Broken Spoor and Galapagos fields). Fahlore-galena-gold assemblage is more typical of chimneys from VHMS deposits of Hokuroko (Cenozoic) and Rudnyi Altai (Paleozoic) ensialic island arc basins.

The contrast trace elements zonation in chimney walls is testified by means of combination of high spatial resolution ICPMS and ultraviolet Nd-YAG laser ablation (LA-ICP-MS) analyses in CODES (Tas-mania University) (methodology in Danyushevsky et al., 2003 and, Large et al., 2009). The highest grades in the most trace elements (Tl, U, Au, Ag, Pb, and Mn) detected for colloform pyrite into outer wall of the chimneys result from rapid precipitation in the high gradient conditions.Coarse-grained layers of chalcopy-rite in the conduits are enriched in Se (155 ppm), Sn (32 ppm), Mo (153 ppm), and (Te (35—130 ppm).

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Some chalcopyrite layers yield the high concentrations of Bi, Au, Ag, Pb, Sb, and As due to precipitation of relevant galena, sulphosalts, and native gold. Sphalerite in the conduits and outer walls has elevated Ag, Au, Sb, As, Pb, and Cd. The trace element concentrations in the outer wall colloform pyrite decrease in the following order, from the outer wall inwards: Tl> Ag> Ni> Mn> Co> As> Mo> Pb> Ba> V> Te> Sb> U> Au> Se> Sn> Bi, governed by the strong temperature and redox gradients. In general, this trace element zonation is similar to that in modern and ancient

black and gray smokers. However, there are differences in some trace element concentrations. This is related to Sb (575 ppm), As (510 ppm) Pb (1444 ppm) and Bi (48 ppm) grades, which are one–two order higher on average than in chalcopyrite of modern black smokers. On the contrary, the Se and Co contents in chalcopyrite of chimneys studied are one-two and more order less than ones in modern black smokers. The trace element composition is similar to that in modern gray smokers with exception of higher Bi and Pb. The later elements are attributive for chimneys from ancient VHMS deposits formed in ensimatic and ensialic island arc basins.

Both zoning in distribution of sulfide mineral types within chimneys, and their trace element contents, are sensitive to a variety of geochemical factors, and thus their study enables an interpretation of the chimney’s growth history, including details of fluid interactions within the chimney walls and composition of foot wall rocks. This study has provided additional information on mineral and trace element distribution within Mesozoic black and gray smoker chimneys.

The research was supported by Presidium RAS (project no. N-09-П-5-1023). The authors are grateful to prof. R.R. Large and prof. Danyushevsky for access to LA-ISPMS analyses. The LA-ICPMS analyses were carried out during a visiting program (2009 y) funded by the ARC Centre of Excellence grant to CODES, University of Tasmania.

RefeReNCeSDanyushevsky, L., Robinson, P., McGoldrick, P., Large, R. and Gilbert, S.,1. 2003. LA–ICPMS of sulfides: Evalu-ation of an XRF glass disc standard for analysis of different sulfide matrixes // Geochimica et Cosmochimica Acta, v. 67, 18, A73 Suppl.Herrington, R.J., Maslennikov, V.V., Spiro, B., Zaykov, V.V., and Little, C.T.S.2. , 1998. Ancient vent chimney structures in the Silurian massive sulfides of the Urals // Modern ocean floor processes and the geological record. Geol. Soc. London Spec. Publ., v. 148. P. 241–257.Large, R.R., Danyushevsky, L.D., Hollit, C., Maslennikov, V.V., Meffre, S., Gilbert, S., Bull, S., Scott, R., 3. Emsbo, P., Thomas, H., Singh, R., and Foster J., 2009. Gold and trace element zonation in pyrite using a laser imaging technique; implications for the timing of gold in orogenic and Carlin-style sediment-hosted deposits // Economic Geology, v. 104. P. 635–668.Little, C.T.S., Herrington, R.J., Haymon, R.M., Danelian, T.,4. 1999. Early Jurassic hydrothermal vent commu-nity from the Franciscan Complex, San Rafael Mounains, California // Geology, v. 27. № 2. P. 167–170.Little, C.T.S., Herrington, R.J., Maslennikov, V.V., Morris, N.J., and Zaykov, V.V.,5. 1997. Silurian high-temperature hydrothermal vent community from the Southern Urals, Russia // Nature, v. 385. P. 3–6. Maslennikov, V.V., Maslennikova, S.P., Large, R.R., Danyushevsky, L.V.,6. 2009. Study of trace element zonation in vent chimneys from the Silurian Yaman-Kasy volcanic-hosted massive sulfide deposits (Southern Urals, Russia) using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) // Economic Geology, v. 104. P. 1111–1141.Maslennikova, S.P., Maslennikov, V.V.,7. 2007. Sulfide chimneys of Palaeozoic black smokers (on the Urals example). Ekaterinburg-Miass: UD RAS. 312 p. Oudin, E., Constantinou, G.,8. 1984. Black smoker chimney fragments in Cyprus sulfide deposits // Nature, v. 308. P. 349–353. Scott, S. D.,9. 1981. Small chimneys from Japanese Kuroko deposits // Seminars on Seafloor Hydrothermal Systems (R. Goldie, T. J. Botrill, eds). Geosci. Canad., v. 8. P. 103–104. Shikazono, N., Kusakabe, M.,10. 1999. Mineralogical characteristics and formation mechanism of sulfate-sulfide chimney from Kuroko area, Mariana Trough and Mid-Ocean Ridges // Resource Geology Special Issue, v. 20. P. 1–11.Zaykov V.V., Novoselov K., Kotlyarov V11. . Native gold and tellurides in the Murgul and Cayely volcanogenic Cu deposits (Turkey) // Au-Ag-Te-Se deposits. IGCP Project 486, Field workshop, Izmir, Turkey, 24-29 Septem-ber 2006. P. 167-172.

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SulfuR iSOTOPiC COmPOSiTiON Of maSSive SulfideS fROm THe SemeNOv HYdROTHeRmal CluSTeR, 13°31’ N, maR

Melekestseva I. Yu.

Institute of Mineralogy, Ural Division of RAS, 456317, Miass, Chelyabinsk district, Russia, e-mail: [email protected]

Introduction. The Semenov massive sulfide hydrothermal cluster discovered in 2007 is located between Marafon and Capo Verde transform faults on a mafic-ultramafic seamount and consists of 5 hydrothermal fields (Beltenev et al., 2007; 2009). Samples of massive sulfides from the Semenov-1, -2, -3, and -4 fields, directly obtained on board of R/V “Professor Logachev” during the 30th cruise in 2007, have been studied for sulfur isotopic composition. The aim of the study is to determine dependences on sulfur isotopic composi-tion from textures and structures of different ore facies which are formed under various seafloor conditions.

Location of hydrothermal fields. The Semenov-1 field is situated in the western foot of the seamount at the depths of 2570—2620 m and, based on TV-works, it is a sulfide mound or several coalescent mounds and products of their destruction (Ivanov et al., 2008). Ultramafic rocks and basalts were dredged in the area of the field. The Semenov-2 field is located on the northwestern seamount slope at the depths of 2480—2750 m on the variously altered basalts. The Semenov-3 field associated with basalts was sampled only once at the depths of 2400—2600 m in the northeastern part of the seamount. The Semenov-4 field also associated with basalts occurs in the eastern part of the seamount both on its foot and slope at the depths of 2850—2950 m.

Massive sulfides of the Semenov-1 field were collected at two stations. Samples of the 30L186 station are fine-grained, sooty, nodule-like, and radial-shaped crystalline marcasite-pyrite aggregates with bar-ite (~20%), opal, and accessory sphalerite and galena (Melekestseva et al., 2010a). Massive sulfides of the 30L292 station are similar by mineral composition with major pyrite and marcasite, subordinate barite and opal, and accessory sphalerite, galena, pyrrhotite, hematite, and jarosite but differ by textures. Sulfides form porous, colloform, nodule, banded, and crystalline aggregates with microscopic layers of pyrite framboids. Sulfide samples from both stations show no fragments of host rocks and their textures are similar to those formed above the seafloor being the parts of the sulfide mounds or diffusers (?). Difference between textures could be explained both by different localization of massive sulfides (inside the mound, on its top or flanks) and the degree of hydrothermal reworking.

Massive sulfides of the Semenov-2 field (station 30L287) are characterized by fine-grained and fine-crystalline structures with major wurtzite, chalcopyrite, and isocubanite, abundant sphalerite, pyrite, mar-casite, covellite, barite, and aragonite and rare pyrrhotite, galena, native gold, and unnamed silver telluride. Cu-Zn assemblage is typical for the black smoker chimneys but no clear zoning in mineral distribution was observed, probably, due to the small size of specimens. Absence of host rock inclusions also indicates their formation above the seafloor.

Massive sulfides of the Semenov-3 area show clastic structure with mostly pyrite clasts from several mm up to 20 cm in size included in a fine-grained sulfide-quartz cement and characterized by colloform, porous, concentric-zonal, massive, and crystalline structure similar to that of massive sulfides from the Semyenov-1 field, station 30L292. A lot of drusoid barite occurs as table-shaped hexagonal crystal aggregates in the cracks and holes of sulfide breccia, sometimes associating with anhedral chalcopyrite grains. The major minerals are pyrite and marcasite with less abundant chalcopyrite and hematite and accessory sphalerite, pyrrhotite, bornite, covellite, and jarosite. Quartz and barite are the main non-opaque minerals.

Massive sulfides of the Semenov-4 site were formed under the seafloor inside the strongly altered ba-salts and are characterized by massive and veinlet-disseminated structure. They have quite simple mineral composition with main pyrite and significantly less abundant marcasite, chalcopyrite, sphalerite, pyrrhotite, hematite, and covellite. Quartz and barite are also components of the veins.

Results of δ34S study. Samples for δ34S study were drilled from sulfides using microdrill with a diamond nozzle. The powders were chemically cleaned using acids. Sulfur isotope compositions of sulfides were mea-sured on SO2 with a MI-1311 mass spectrometer (IGEM RAS, Moscow, analyst L.P. Nosik). Analyses are reported as standard δ notation relative to Canyon Diablo Troilite (CTD). Sulfur isotope ratio showing a difference in the isotopic composition in sulfides is given in Table.

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δ34S in samples from the Semenov-1 field, st. 30L186, vary between –3.03 and –3.26‰ for the early sulfides (Table, no. 186-2-a, b) to –0.80 and –1.09‰ for the late sulfides (Table, no. 186-1-a, b). Massive sulfides from the st. 30L292 of the same field have higher sulfur isotope ratio in comparison with sulfides of the 30L186 station, between +1.40 and +1.53‰ for the early sulfides (Table, no. 292-1-1a, b) to –0.07 and –0.08‰ for the late sulfides (Table, no. 292-2-a, b). Cu-Zn sulfides from the Semenov-2 area show posi-tive δ34S values ranging from +3.27 and 3.41‰ for the early Cu-assemblage (chalcopyrite+isocubanite, Table, no. 287-2-a, b) to +1.78 and +1.79‰ for the late Zn-sulfides (sphalerite+wurtzite, Table, no. 287-1-a, b). Sulfides from breccia of the Semenov-3 field have δ34S which varies from +0.67 and +0.69‰ (Table, no. 284-1, a, b), +1.37 and +1.51‰ (Table, no. 284-3, a, b) to +3.74 and +3.88‰ (Table, no. 284-2-a, b). Pyrite from the Semenov-4 field has δ34S values ranging from +1.53 and +1.66‰ (Table, no. 145-1, a, b). The lightest δ34S value of –7.52‰ was determined for pyrite in strongly altered basalts of the Semyenov-4 field.

Discussion. The light δ34S values of the early low temperature (< 300 °C) fine-grained sooty Fe-sulfides (Semenov-1, st. 30L186), which crystallized after euhedral barite aggregates [Melekestseva et al., 2010b], suggest (i) fractionation of sulfur between early barite with heavy δ34S value and following early Fe-sulfides with light sulfur isotopic ratio due to disproportional reaction 4SO2 + 4H2O = 3H2SO4 + H2S at T < 300 °C (Ohmoto, Rye, 1979) and, in the same time, (ii) that reduction of SO4 from the seawater was not involved in the precipitation of sulfides, probably, related to the gradual infiltration of hydrothermal fluids inside the sulfide edifice. From the other side, the higher δ34S values of the late sulfides relatively the early generation may already reflect some mixing of hydrothermal fluid enriched in light sulfur isotope with seawater at the late stage of sulfide precipitation.

Fe-sulfides of the st. 30L292 (Semenov-1) differ by textures and also δ34S values from Fe-sulfides described above. Early porous colloform (with microscopic framboids) pyrite reflecting its rapid precipi-tation from the very saturated solutions displays a little involvement of SO4 from the seawater whereas the late crystalline pyrite has slightly lighter δ34S values, probably, due to its crystallization in a “closed” sulfide mound.

Tendency of changing of δ34S values depending on textures of Fe-sulfides in clastic facies (st. 30L284, Semenov-3) generally correspond to the Fe-sulfides from the Semenov-1 field. Sulfide clasts with porous

T a b l eSulfur isotopic data (δ34SCTD‰) for sulfides of the Semenov hydrothermal cluster, MAR

Hydrothermal field

Samples Pyrite Pyrite ± marcasite Cu-sulfides Zn-sulfides Brief textural-temporal description of sulfides

Semenov-1 186-1-a –0.80 Early sooty and extremely fine-grained186-1-b –1.09186-2-a –3.03 Late radial-shaped crystalline186-2-b –3.26292-1-a +1.40 Early porous292-1-b +1.53292-2-a –0.07 Late crystalline292-2-b –0.08

Semenov-2 287-2-a +3.27 Early crystalline287-2-b +3.41287-1-a +1.78 Late crystalline287-1-b +1.79

Semenov-3 284-1-a +0.67 Colloform-crystalline sulfide clast284-1-b +0.69284-3-a +1.37 Porous sulfide clast284-3-b +1.51284-2-a +3.74 Very porous and colloform sulfide clast284-2-b +3.88

Semenov-4 145-1-a +1.53 Massive crystalline145-1-b +1.66 Veined crystalline153-1 –7.52

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(Table, no. 284-3) and very porous (Table, no. 284-2) textures have higher sulfur isotopic ratio reflecting mixing of hydrothermal fluid and seawater like porous Fe-sulfides from the Semenov-1 field (Table, no. 292-1). At the same time, the presence of late crystalline sulfides in the clasts (Table, no. 284-1) leads to the decreasing of δ34S value like in similar case from the Semyenov-1 field (Table, no. 292-2).

Cu-Zn-sulfides of the Semenov-2 field with positive δ34S values have clear indication of the involvement of SO4 from the seawater in their precipitation and are characterized by decreasing of δ34S values from the early high temperature (> 300°C) Cu-Fe-minerals (chalcopyrite and isocubanite, Table, no. 287-2) to the late relatively low temperature (< 300°C) Zn-assemblage (sphalerite and wurtzite, Table, no. 287-1). A little bit similar tendency of lightening of δ34S values in Zn-sulfides in comparison with Cu-sulfides was observed in the black smoker chimneys of the Rainbow field (Lein et al., 2003). Another tendencies can be also deter-mined (Bortnikov, Vikent’ev, 2005).

Massive crystalline pyrite from the Semenov-4 field shows quite typical positive sulfur isotopic values (Table, no. 145) but coarse-grained pyrite from the veins in strongly altered basalts has unusual light δ34S value of –7.52‰ comparable only with pyrite from the Hine Hina field (Herzig et al., 1998) and chalcopy-rite of the Lucky Strike field (Bortnikov, Vikent’ev, 2005).

Conclusion. δ34S values of Semenov cluster sulfides (–7.52…+3.88‰) generally fall into the measured sulfur isotopic ratio interval in sulfides from oceanic hydrothermal fields (–7.7…+16.2‰) which reflect the sulfur involvement from different sources (Herzig et al., 1998; Bortnikov, Vikent’ev, 2005). The most wide-spread δ34S values of oceanic sulfides are greater than 0‰ suggesting the mixing of magmatic and seawater sulfur that we suggest for the Cu-Zn sulfides of the Semenov-2 and FeS2 from the Semenov-3 and -1 fields.

Negative δ34S values are peculiar for several hydrothermal fields, e.g. Lucky Strike (–7.0…+13.3‰), Broken Spur (–0.8…+1.4‰), Logatchev (–0.6…+12.3‰), Rainbow (–3.5…+5.0‰), PACMANUS (–1.0…+2.6‰) (compilation in Bortnikov, Vikent’ev, 2005), and sulfides of the Guaymas basin (–3.7…+4.5‰) (Peter, Shanks, 1992). Only negative δ34S values were measured in sulfides of the three hydrother-mal fields: Hine Hina (–7.7…–2.8‰), Lau back-arc basin (Herzig et al., 1998), Loihi volcano (–2.17…–0.7‰), Hawaii islands (Davis et al., 2003), and studied Semenov-1 (st. 30L186) and -4 (st. 30L153) (see Table). Excluding biogenic reduction of seawater SO4 in all three cases, explanation of the light δ34S values mostly involves magmatic input which leads to the boiling of the hydrothermal fluid and fractionation of sulfur between reduced and oxidized species as a result of large shifts in the oxidation state of the fluids or evolution of light sulfur directly from a magmatic volatile phase (Herzig et al., 1998 and many others). Disproportion of SO2 with H2SO4 producing in case of the Semenov-1 and -4 sulfides has led to the oxi-dation conditions and formation of barite from Na2SO4–K2SO4–Н2О и Na2SO4–NaНСO3–Н2О solutions (Semenov-1) (Melekestseva et al., 2010b) and strong acid alteration of hosted basalts (Semenov-4).

Together with different sources of sulfur we also would like to note that (i) the same minerals (e.g., pyrite) with different textures which reflect the different formation conditions have different δ34S values; (ii) there are tendencies of changing (increasing or decreasing) of δ34S values depending on temporal as-semblages both for the same and different minerals; and (iii) temperature and pH–Eh conditions also play an important role in sulfur differentiation along with other factors.

Author is grateful to V.N. Ivanov and V.E. Beltenev (Polar Marine Geosurvey Expedition, St. Peters-burg) for the possibility of sampling, L.P. Nosik (IGEM RAS, Moscow) for carrying out of analyses, and V.V. Maslennikov (IMin UB RAS) for discussion of results.

This study is supported by the Presidium of RAS (project no. 09-П-5-1023).

RefeReNCeSBeltenev V., Ivanov V., Rozhdestvenskaya I. et al.1. A new hydrothermal field at l3°30’ N on the Mid-Atlantic Ridge // InterRidge News, 2007. Vol. 16. P. 9–10.Beltenev V., Ivanov V., Rozhdestvenskaya I. et al.2. New data about structure of hydrothermal fields in the area of l3°31’ N (Semenov ore cluster) // In: Material of the XVIII school on Marine Geology “Geology of Seas and Oceans”. Moscow, 2009. Vol. II. P. 133–136.Bortnikov N.S., Vikent’ev I.V.3. Modern Base Metal Sulfide Mineral Formation in the World Ocean // Geol. of Ore Deposits, 2005. Vol. 47. № 1. P. 13–44.Davis A.S., Clague D.A., Zierenberg R.A. et al4. . Sulfide formation related to changes in the hydrothermal system on Loihi seamount, Hawai’i, following the seismic event in 1996 // Can. Miner., 2003. Vol. 41. P. 457–472.Herzig P.M., Hannington M.D., Arribas A.Jr. 5. Sulfur isotopic composition of hydrothermal precipitates from the Lau back-arc: implications for magmatic contributions to sea-floor hydrothermal systems // Miner. Deposita, 1998. Vol. 33. P. 226–237.

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Ivanov V., Beltenev V., Stepanova T.V. et al.6. Sulfide ores of the new hydrothermal cluster l3°31’ N of MAR // Metallogeny of ancient and modern oceans-2008. Ore-bearing complexes and ore facies. Miass, Institute of Mineralogy UD RAS, 2008. P. 19–22.Lein A.Yu., Cherkashev G.A., Ul’yanov A.A. et al.7. Mineralogy and Geochemistry of Sulfide Ores from the Logachev-2 and Rainbow Fields: Similar and Distinctive Features // Geochem. Intern., 2003. Vol. 41. № 3. P. 271–294.Melekestseva I.Yu., Kotlyarov V.A., Ivanov V.N. et al8. . Massive sulfides of the new hydrothermal sulfide cluster Semenov (13°31'N), Mid-Atlantic Ridge // Lithosphere, 2010a. № 2. P. 47–61.Melekestseva I.Yu., Yuminov A.M., Nimis P.9. Massive sulfides of the Semenov-1 hydrothermal field: textures, mineralogy, and forming conditions // In: Metallogeny of ancient and modern oceans-2010. Ore potential of spreading and island arc structures. Miass: IMin UB RAS, 2010b. P. 56–61.Ohmoto H, Rye R.O10. . Isotopes of sulfur and carbon. In: Barnes HL (ed) Geochemistry of hydrothermal ore deposits. J. Wiley and Sons, New York, 1979. P 509–567.Peter J.M., Shanks W.C11. . III. Sulfur, carbon, and oxygen isotope variations in submarine hydrothermal de-posits of Guaymas Basin, Gulf of California, USA // Geochim. et Cosmochim. Acta, 1992. Vol. 56, Iss. 5. P. 2025–2040.

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SOuRCeS aNd GeNeSiS Of HYdROCaRBONS iN THe BOTTOm SedimeNTS Of HYdROTHeRmal fieldS

aSHadZe-1 aNd aSHadZe-2 (maR, 13°N)

Morgunova I.P., Petrova V.I., Kursheva A.V., Litvinenko I.V., Stepanova T.V., Cherkashev G.A.

I.S. Gramberg All-Russia Research Institute for Geology and Mineral Resources of the World Ocean (VNIIOkeangeologiya) Angliysky pr., 1, St.-Petersburg 190121 Russia Fax: +7 812 714 14 70, e-mail: [email protected]

Properties and composition of dispersed organic matter (DOM) of deep sediments from the mid-oce-anic ridges are of particular interest for study the biogeochemical processes of hydrothermal active zones of the oceanic rifts. The increasing of the world scientific attention to this phenomena and related processes associated with the hydrothermal ore formation is caused not only by the practical meaning of the new ocean resources developing, but also the specificity of extreme environmental conditions typical for submarine volcanic zones. The rift hydrothermal circulation system is a complex geostructural formation, which can be used as a model of natural laboratory for detail geological, geophysical, geochemical, biological and other researches. The enormous amounts of heat released with the endogenous fluid into the near-bottom layers and their enrichment with highly mineralized substance during the fluid discharge stimulates development of unique chemosynthetic biocenoses. The specific patterns of diagenetic transformation of autochthonous chemotrophic organic and allochthonous organic matter (OM) are influenced by set of physical and chemi-cal factors with temperature as the leading [1, 2].

As a result of joint work of PMGE and VNIIOkeangeologiya during the 22 cruise of the R/V “Professor Logachev” in 2003 the two hydrothermal fields Ashadze-1 and Ashadze-2 (13°N, MAR) were discovered. The significant part of work was conducted during the French-Russian expedition “Serpentine” on-board «Pourquoi Pas» in 2007 [3, 4]. The ore cluster “Ashadze” is hydrothermally active. During the common work there were identified five groups of active chimney edifices on the first field and one active crater structure on the second.

Samples of sediments (9 stations, 31 sample) were collected using box-corer, TV-grab and drag and kept until the laboratory investigations in sterile containers at –18°C. The standard analytical procedure included determination of elemental (Corg, Norg, Ccarb) composition of sediments and group and molecular composi-tion of the soluble part of the DOM by methods of preparative liquid chromatography and GC-MS using Agilent Technologies GC System 6850/5973.

The comparative study of bottom sediments collected directly from the hydrothermal fields Ashadze-1 and 2 with distant background pelagic sediments was conducted. Low-carbonate muds and hydrothermal metalliferous sediments cardinally differ by their geochemical characteristics from the background samples: organic carbon content is sufficiently low Corg = 0.1 ÷ 0.6%, while the hydrocarbons reach in the surface layer 234.4 µg/g of sediment, which is an order of magnitude greater than background values (~26 µg/g of sediment). For comparison, the amount of hydrocarbons in surface sediments of the ore field TAG (1993, R / V “Professor. Logachev”) reaches values of ~170.4 µg /g of sediment. In contrast to the background, hydrothermal samples contain relatively less residual organic matter (for some samples ROM <84% dry sed.) together with a sufficiently high bituminousity β>10. In the group composition of DOM an increasing content of oil fraction is indicated and it reaches maximum values in the sediments of hydrothermal fields Ashadze-1 (Fig. 1, a).

The content of n-alkanes varies both in background and hydrothermal samples (Fig. 1 b, c). Bimodal type of distribution and strong odd-even domination for high-molecular homologues C27 ÷ C31 (allochtho-nous higher plants) is typical for background sediments [5]. A significant contribution of native transformed biogenic matter (CPI ~ 1 ÷ 3, Pristane/ Phytane <0.2) in composition of DOM and an increase of hydrobi-otic components C19 ÷ C21 was fixed in several samples. Surprisingly high degree of DOM maturity (OEP ~ 1) in one of background station surface sediments agrees with fixed nearby hydrophysical anomaly of water (T°, salinity and turbidity) [6], and indicates the active thermal catalytic alteration of DOM.

The distribution of n-alkanes in hydrothermal sediments is less homogeneous and has a number of specific features. Thus, isoprenoids (Cn<25) dominate in the Ashadze-1 surface sediments and the highest content of hydrobiotic type of n-alkanes (C17-19/C27-31 ~ 3 ÷ 4.6) is typical for Ashadze-2. The phytane index values for the second field (K18=7.1) indicate the presence of a local source of OM (microbial), and the

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odd-even preference index OEP ~ 1 (for n-C <21 and C27 ÷ C31) points to the thermal catalytic alteration process of authochthonous and allochthonous OM components.

A characteristic feature of the aliphatic HCs mass spectra (m/z 71) for both hydrothermal zones is the presence of three intense peaks in the high molecular weight region (C37 ÷ C41). Their genesis and structure determination requires more detailed study, but detected similarity allows us to assume the existence of common processes of DOM formation, connected one or another way with the influence of hydrothermal environmental conditions.

Terpenoid mass chromatograms (hopanes m/z 191 and steranes m /z 217) characteristic for background areas indicate regular supply of biogenic material in sediments, while the availability of resistant to biodeg-radation cheilanthanes and diasteranes and the ratio for sterane isomers C29 20S/(20S +20R) ≥ 0.5 points to postdiagenetic stage of DOM transformation [5, 7, 9].

Situation changes significantly in the transition to the hydrothermal area. Cyclanes distribution in sur-face sediments of hydrothermal field Ashadze-1 indicates a low level of DOM transformation (Ts / Tm = 0.23), and the presence of hopenes and ββ-biohopanes confirms the fresh biogenic input to the sediments.

The singularity of hopanes and steranes chromatographic distribution in sediments of Ashadze-2 may be associated with the presence of specific sources of biogenic matter and strong influence of hydrothermal

Fig. 1. Comparative distribution of the geochemical parameters in the surface sediments of hydrothermal samples (a); distribution of n-alkanes in sediments of the background station (b) and hydrothermal stations Ashadze-2 (c).

Fig. 2. Cyclanes distribution in the bottom sediments: (a) — steranes mass spectra (Ashadze-2), (b) — hopanes mass spectra; (c) — steranes total content in all surface samples

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processes on the biogenic substances transformation. With all that the amounts of steranes in samples of both fields are significantly higher than the background values and reach ~ 180 ng/g (Fig. 2 a, b).

Polyaromatic hydrocarbons (PAHs) in the background sediments are the minor part of DOM and are presented by standard set of compounds, but their content is higher than that for the background abyssal areas and reaches values up to 90 ng /g [8]. This accounts for the bulk of phenanthrene and its methyl homologues with high transformation degree (MPI1 = 0.6 ÷ 0.9). The pyrogenic polyarenes composition (Flu/Pyr >1) points to a significant influence of far aerosol transfer of PAH [10]. This fact is consistent with the presence of components in sediments typical for continental DOM (n-alkanes C27÷31, steranes C29).

Within two hydrothermal fields Ashadze-1 and 2 the phenanthrene structures dominate in common PAH composition and the pyrogenic component (fluoranthene and pyrene) is also detected. The highest polyarenes content among the studied material was fixed for the Ashadze-2 sediment section (ΣPAH = 262 ng / g), mainly because of phenanthrene and its mono-and bi-methil homologues (178, 192 and 206 m.m.) high values. The anomalously high amounts of parent phenanthrene accompanied by an increase of the sterane total contents may point to the DOM in situ thermal catalytic alteration process [11, 12].

Thus, the result of two active hydrothermal fields Ashadze-1 and 2 investigation suggests the existence of similar sources and mechanisms of DOM generation for them. The similarity may be connected both with the influence of biological communities, distributed mainly in sites of hydrothermal activity, and with speci-ficity of biogenic OM transformation under the whole set of physical and chemical factors of hydrothermal environment.

Acknowledgments - We thank the Polar Marine Geosurvey Expedition for providing materials, selected during 22-nd and 30-d cruises of the R/V “Professor Logachev” and funded by the Federal Subsoil Resourc-es Management Agency of the Ministry for Natural Resources and Ecology of the Russian Federation.

RefeReNCeSHydrothermal systems and sedimentary formations of the mid-oceanic ridges of Atlantic Ocean / Lisitsin A.P., 1. Bogdanov A.U., Gordeev V.V. et al. Moscow: Nauka, 1993. – 256 p.Hydrothermal formations of the ocean rift zones / Lisitsin A.P., Bogdanov A.U., Gurvich E.G. Moscow: 2. Nauka, 1990. – 256 с.Fouquet Y., G. Cherkashov, J.L.3. Charlou et. al. Serpentine cruise - ultramafic hosted hydrothermal deposits on the Mid-Atlantic Ridge: First submersible studies on Ashadze 1 and 2, Logatchev 2 and Krasnov vent fields // InterRidge News. 2008. V. 17. P. 15-19. Bel’tenev V., A. Nescheretov, V. Shilov et. al.4. New discoveries at 12° 58'N, 44° 52'W, MAR: Professor Logatchev-22 cruise, initial results // InterRidge News. 2003. V. 12. № 1. P. 13-14.Peters K., Moldowan J.5. The biomarker guide. Interpreting Molecular Fossils in petroleum and ancient sedi-ments/ New Jersy, 1994,364 p.Kaminski D.V., Narkevski E.V., Sudarikov S.M6. . Structure of the near bottom water plumes at 12°58'N, MAR. Materials from 26 International Scientific conference (school) of marine geology. V. 2. Moscow. GEOS. 2007. 324 p. Yamanaka T., Ishibashi J., Hashimoto J.7. Organic geochemistry of hydrothermal petroleum generated in the submarine Wakamiko caldera, southern Kyushu, Japan // Organic Geochemistry. 2000. V. 31. P. 1117-1132.Petrova V.I.8. Geochemistry of polycyclic aromatic hydrocarbons in bottom sediments of the World Ocean. Ab-stract of doctoral dissertation in geology-mineralogical science: 04.00.10, 04.00.02. St.Petersburg, 1999. 30 p.Boni M., Simoneit B.R.T., Fruh-Green G.L. et al9. . Organic matter and carbon isotope composition of carbonate nodules and associated sediments from Middle Valley, Leg 139 // Proceedings of the ODP, Scientific Results. 1994. V. 139. P. 329-339.Yunker M., Macdonald R., Walter J. et al.10. Alkane, terpene, and polycyclic aromatic hydrocarbon geochemistry of the Mackenzie River and Mackenzie shelf: Riverine contributions to Beaufort Sea coastal sediment // Geo-chimica et Cosmochimica Acta. 1993. V. 57. P. 3041-3061.

77

THe ReSulTS Of HYdROPHiSiCal exPlORaTiONS iN THe aTlaNTiC OCeaN duRiNG THe 32TH CRuiSe

ON THe Rv “PROfeSSOR lOGaCHev”

Narkevskiy E.1, Gustaytis A.1 and Ermakova L.2

1Polar Marine Geosurvey Expedition, Saint-Petersburg, Lomonosov, e-mail: [email protected], 2VNIIokeangeologia, Saint-Petersburg, e-mail: [email protected]

In the 32th cruise on the RV “Professor Logachev” organized by Polar Marine Geosurvey Expedition (PMGE) there were done geological and geophysical researches. One of the main aims was to reveal the signs of the modern hydrothermal activity within two sections:

1) The first one is located in the hydrothermal valley which is a segment of Mid-Atlantic Ridge (from 11° till 12°30' N)

2) The second — is a part of ore cluster “Semenov” around underwater mount 13°30' NDuring the hydrophisical survey there were found two places with signs of modern hydrothermal activity

within the first section.The first place is at the bottom of the rift valley in the region of new volcanic rise in latitude 11°24'—

11°27' N. Station 32л125 was made just on the top of new volcanic rise with a depth 3840 m, here in the near-bottom seawater layer between 3600 and 3500 m there were observed significant jumps of all hydrophysical parameters including turbidity (FTU), potential temperature (θ), salinity (S) and density (D) so typical for hydrothermal plumes (Fig. 1). While lowering the СTD the turbidity was quickly rising from the horizon 3520 m, the maximum value (0.070 FTU) was achieved on the depth equal to 3540 m. After that the turbid-ity decreased, and after 10 m it began to rise again. Therewith the first turbidity jump was accompanied by slight decreasing of salinity (~0.003 ‰), potential temperature (0.020°C) and density. However the second turbidity jump was not accompanied by changing of hydrophysical parameters.

Three days later for the purpose of revealing the structure of hydrothermal plume there were made four hydrophysical stations at the new volcanic rising with a distance ~500 m between each other. The depth’s amplitude was not more than 10 m. Consequently the hydrothermal plume was observed along the new vol-canic rise nearly for 1000 m. The longitudinal spreading of plum was not explored.

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The second place is located in the southern part of the studied segment of MAR on the eastern edge of the rift valley. On the station 32L132 which is on the slope in the bottom layer of seawater were registered abnormal profiles of turbidity and thermohaline characteristics. Starting from the horizon ~3800 m we can see the increasing of turbidity function which has its maximum value (it is ~0.054 FTU) on the depth 3980 m (Fig. 1). Such kind of vertical distribution continues till the very bottom. So significant changes of po-tential temperature (∆ θ =0.158°C over the range of 1 m) probably is an evidence of the closest heat source neighborhood. It can be related with hydrothermal nature. In addition, so complex structure of thermoha-line characteristics distribution can be caused by complicated slop hydrodynamic processes. More detailed explorations were not made.

It stands to mention that nearby the station 32L132 hydrothermally altered rocks with a sulphide miner-alization were picked up by dredge. Thus, on the segment of MAR located in latitude 11°00'–11°30' N there were discovered two places kindly for hydrothermal multimetallic sulphides.

Within the second section (ore cluster “Semenov”) around the ore fields “Semenov-1” (st. 32L250) and “Semenov-2” (st. 32L243, 32L266, 32L267) there also were found evidences of the modern hydrothermal activity.

Firstly on the ore field “Semenov-1” we observed insignificant periodical potential temperature jumps in seawater layer starting from 2270 m. And finally in the bottom 60 m layer beneath the horizon 2480 m we noticed the turbidity jump. In tote the turbidity fluctuations were from 0,012 FTU to 0,049 FTU. Taking into account that the station was put on the ore field, we can suggest the slight hydrothermal activity as the explanation of the turbidity and temperature profiles.

On the ore field “Semenov-2” the traces of hydrothermal activity are registered three times — on st. 32L243, 32L266 and 32L267.

Numerous and frequent oscillations of potential temperature were observed on st. 32L243 in range of 2330—2360 and 2440—2480 m. The maximum value of the amplitude (0.0383° С) was registered in 2560–2610 m seawater layer. We can see the increasing of turbidity up to 0.031 FTU in layer 2260—2610 m. No-table that the layer of high turbidity values agrees with potential temperature oscillations layer.

On st. 32L266 which is situated 1.2 km in southwest direction from st 32L243 we also see a number of po-tential temperature jumps with higher amplitude in layer 2310—2360 m. The maximum value is 0.0590°С.

On st. 32L267 (1.7—km southwest from st 32L243) there were observed a number of potential tempera-ture inversions with a maximum amplitude 0.0276° С (seawater layer 2200—2210 m). The turbidity changes here are insignificant: the interval is 0,014-0,019 FTU.

Thereby, the hydrophisical analysis of potential temperature and turbidity vertical distributions on sta-tions 32л243, 32л266 и 32л267 shows us the presence of the modern hydrothermal activity in this place. Above all it was confirmed during video profiling of the oceanic bottom in this section (ore cluster “Se-menov”).

Summary1. In the region of new volcanic rise was discovered the hydrothermal plume, which was retraced in

meridional direction for the distance of 1000 m. In other direction it was not explored. The plum definitely is an evidence of the modern hydrothermal activity.

2. On points 32L132 and 32L133 (south of the section), where gabbroid with atacamite mineralization had been picked up earlier, there were observed abnormal profiles of turbidity and thermohaline charac-teristics in the bottom seawater layer. These kind of thermohaline vertical distributions are not typical for hydrothermal plumes. Significant jumps of potential temperature tell us the source of heat is close by and it can be hydrothermal by its nature.

3. By means of hydrophisical survey we observed the modern hydrothermal activity on several stations in the region of “Semenov-1” and “Semenov-2”. Moreover it is confirmed by video observations at the oceanic bottom.

The 32 cruise RV “Professor Logachev” was organized by PMGE and financed by the Federal Agency for Subsurface Use of Natural Resources Ministry of Russian Federation.

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THe PaliNuRO vOlCaNiC COmPlex (TYRRHeNiaN Sea): iNORGaNiC aNd miCROBial SulfuR CYCliNG

aS Revealed BY mulTiPle SulfuR iSOTOPe daTa

Peters Marc 1; Harald Strauss1, Sven Petersen2, Nicolai-Alexeji Kummer3, Christophe Thomazo1,4

1Westfälische Wilhelms-Universität Münster, Institut für Geologie und Paläontologie, Corrensstr. 24, 48149 Münster, Germany. e-mail: [email protected], Gebäude Ostufer, Wischhofstr. 1 – 3, 24148 Kiel, Germany3TU Bergakademie Freiberg, Lehrstuhl für Hydrogeologie, Gustav-Zeuner-Str. 12, 09596 Freiberg, Germany4Université Denis Diderot Paris 7, Institut de Physique du Globe de Paris, 75251 Paris Cedex 05, France

Seafloor hydrothermal systems in subduction related tectonic settings differ from those at mid-ocean ridges because of their shallow water depth (<1600 m), their host rock composition, and the magmatic contribution of volatiles and metals to the convecting hydrothermal system (Hannington et al., 2005). The location of fluid venting at lower hydrostatic pressure increases the likelihood of boiling during fluid ascent and venting. Magmatic degassing or magmatic contributions of volatiles at hydrothermal systems in island arc settings are likely to be important due to the higher H2O content of the magmas when compared to those at mid-ocean ridges. This is indicated by the discovery of liquid sulfur lakes, low pH-fluids, liquid CO2 dis-charge, and ongoing SO2-rich eruptions along the Mariana Arc (Embley et al., 2004). The strong acidity of some of these vent fluids has been attributed to the magmatic contribution of SO2, which disproportionates to H2S and H2SO4 during cooling (Herzig et al., 1998; Embley et al., 2004; Kim et al., 2004) highlighting the possible importance of magmatic volatiles on the sulfur budget at island arc hydrothermal system.

Shallow water hydrothermal activity, although most important along the western Pacific, has also been documented from the Tyrrhenian Sea, off-shore Sicily, where it caused the formation of massive sulfide min-eralizations (Marani et al., 1997; Dekov and Savelli, 2004). Recent drilling of these deposits allows studying the various processes responsible for the formation of shallow marine hydrothermal systems associated with island arc volcanism. This study centers on the Palinuro volcanic complex at the Aeolian island arc (Tyrrhe-nian Sea) near Italy (Fig. 1). Dissolved sulfide concentrations, pH and Eh were determined for pore water from sediments, as well as the isotopic compositions of metal sulfides, elemental sulfur and barite precipi-tates in sediments and from the massive sulfide complex of Palinuro. This allows conclusions to be drawn in respect to the formation process of the structures at hydrothermal systems associated with submarine arc volcanoes and the role of microbial life. The two study sites were sampled during the research cruise M73/2 with the German RV “Meteor” in 2007.

δ34S values for pyrite between -32.8 and +0.5‰, elemental sulfur with values between -26.7 and -1.1‰ and barite with values between +25.0 and +33.0‰ (Fig. 2) from the Palinuro massive sulfide complex indi-cate a strong influence of a microbial community presumably consisting of sulfate reducers, sulfide oxidizers and sulfur disproportionators. Isotope data reveal that both sulfide and native sulfur mainly result from mi-crobial sulfur cycling even if a contribution of magmatic SO2 to the mineralization is very likely. This under-lines the importance of microbial activity in hydrothermal systems particularly with respect to the formation of massive sulfide even in volcanic settings with a notable but minor sediment influence.

Multiple sulfur isotopic mea-surements for the sedimentary CRS fraction provide δ34S values be-tween — 29.8 and +10.2‰ and Δ33S values for sediments from one core between +0.015 and +0.134‰

Fig. 1. Map of the southeastern Tyrrhe-nian Sea showing the Marsili back-arc basin and the Aeolian Island Arc with the Palinuro volcanic complex (modi-fied after Beccaluva et al., 1985).

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(Fig. 3). The data suggest a direct re-lationship between hydrothermal and microbial activity. Additionally, pore water from Palinuro’s sulfide bearing sediments yields a broad range in dis-solved sulfide concentration between 1 and 537µmol/L, pH values between 6.10 and 7.67 and Eh values between -162 and +312mV. Hence, pore water chemistry reflects the pertinent redox conditions and a variable influence of hydrothermalism, depending upon the position of the core in respect to the center of hydrothermal activity.

In summary, combined δ34S/Δ33S analyses, applied here for the first time to samples from a hydrothermal system at an island arc setting, reveal the im-portance of microbial communities for the origin of massive sulfide mineraliza-tions and sedimentary sulfide in the hy-drothermal subsurface. Hence, multiple sulfur isotope measurements supple-mented with basic geochemical param-eters provide a deeper understanding of the pertinent processes in the subsurface of hydrothermal systems.

Fig. 2. δ34S vs. sediment depth for massive sulfide, elemental sulfur and barite from the Palinuro volcanic complex.

Fig. 3. δ34S vs. Δ33S for sedimentary sul-fide from Palinuro. Curved line repre-sents δ34S vs. Δ33S values for hydrother-mal sulfide in isotope equilibrium with dissolved sulfate. Numbers on the curve are isotopic equilibrium temperatures. Also presented is the field for sulfide pro-duced during bacterial sulfate reduction.

RefeReNCeSDekov, V.M. and Savelli, C.1. , 2004. Hydrothermal activity in the SE Tyrrhenian Sea: an over-view of 30 years of research. Marine Geology 204, 161-185.Embley, R.W., Baker, E.T., Chadwick, W.W., Jr., Lupton, J.E., Resing, J.A., Massoth, G.L., Nakamura, K.2. , 2004. Explorations of Mariana arc volcanoes reveal new hydrothermal systems. EOS Transactions American Geophysical Union 85, 37-44.Hannington, M.D., de Ronde, C.E.J., Petersen, S.3. , 2005. Sea-floor tectonics and submarine hydrothermal sys-tems. In: Hedenquist, J.W. (Ed.), Economic Geology 110th anniversary volume. Society of Economic Geolo-gists, Littleton, 111-141.Herzig, P.M., Hannington, M.D., Arribas,A.4. , 1998. Sulfur isotopic composition of hydrothermal precipitates from the Lau back-arc: Implications for magmatic contributions to seafloor hydrothermal systems. Mineral Deposita 33, 226-237.Kim, J., Lee, I., Lee, K.Y.5. , 2004. S, Sr, and Pb isotopic systematics of hydrothermal chimney precipitates from the Eastern Manus Basin, western Pacific: Evaluation of magmatic contribution to hydrothermal system. Journal of Geophysical Research 109, B12210.Marani, M.P., Gamberi, F., Casoni, L., Carrara, G., Landuzzi, V., Musacchio, M., Penitenti, D., Rossi, L., Trua, T.6. , 1999. New rock and hydrothermal samples from the southern Tyrrhenian Sea: The MAR-98 research cruise. Giornale di Geologia 61, 3-24.

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mOdeRN SeaflOOR maSSive Sulfide dePOSiTS: diSTRiBuTiON, ORe TYPeS, aNd eCONOmiC SiGNifiCaNCe

Petersen, Sven

IFM-GEOMAR, Kiel, Germany

Despite the recent economic downturn, there is still interest in the economic potential of seafloor mas-sive sulfides. There are currently a few companies that have claimed areas for exploration licenses in the territorial waters of Papua New Guinea (PNG), Tonga, Fiji, New Zealand and other countries. This pre-sentation deals with the variability of presently known seafloor hydrothermal systems and their likelihood to become an economic target or even a major metal resource in the future.

Currently more than 300 sites of seafloor hydrothermal activity are known on the ocean floor; about 240 of these are sites of confirmed high-temperature venting (black smokers) with associated polymetallic sulfide deposits. These deposits have been documented in all oceans and recent advances in technology have increased the speed at which such systems are found on the modern seafloor. Investigations of these systems over the past decade revealed important variations in their geological setting not previously recognized on the modern seafloor. Hydrothermal systems along mid-ocean ridges vary dramatically, from small scale pin-nacles to large steep-sided chimneys and mounds occurring in water depths ranging from 5000 m to as shal-low as 100 m. However, even greater variability is found along submarine portions of volcanic island arcs and back-arc basins, where hydrothermal systems dominated by CO2-discharge as well as systems enriched in SO2 with lakes of native sulfur have recently been observed.

Economic feasibility of mining of seafloor massive sulfides can only be shown by drilling. Several at-tempts to drill sulfide deposits were made in the past. However, they often showed disappointing results from an economic point of view. These results highlight even further the importance of seafloor drilling to validate grades and tonnages of seafloor massive sulfides that are often only based on surface sampling using submersibles, ROV’s or TV-guided grabs. With the existing database and lacking information on the third dimension it seems premature to comment on the economic significance of seafloor massive sulfides. Pub-lished geochemical analyses of sulfide samples indicate that some deposits may contain important metal concentrations, however, currently only ~10 deposits may have sufficient size and grade to be considered for future mining. Additionally, other factors such as water depth, distance to land, and jurisdiction also impact the economic potential. Marine mining appears to be feasible under specific conditions ideally including (1) high gold and base metal grades, (2) site location close to land, i.e., commonly within the ter-ritorial waters of a coastal state, (3) water depths below ~3000 m. Under these circumstances, massive sul-fide mining can be economically attractive considering that the mining system is likely portable and can be moved from one site to another. Given the limited sulfide tonnage presently known on the modern seafloor when compared to the geological record, mining of black smoker deposits might occur in the not so distant future, but it seems unlikely, that seafloor massive sulfides will be a substantial metal resource for humankind as often suggested. The search for hydrothermal systems on the modern seafloor has resulted in the discovery of a high proportion of small, widely-spaced deposits which is in contrast to land-based exploration where the larger deposits tend to be found early on. However, large, inactive deposits may exist in isolated areas or under thick sediment cover that are more difficult to identify by current exploration methods.

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defORmaTiON mOdel Of HYdROTHeRmal Sulfide ORe fieldS fOR PRediCTiON Of HYdROTHeRmal aCTiviTY lOCaTiONS

(fOR diffeReNT aReaS Of THe aTlaNTiC aNd iNdiaN OCeaNS)

Petukhov S.I., Alexsandrov P.A., Andreev S.I.

VNIIOkeangeologia, Angliysky Prosp., 1, St. Petersburg, 190121, Russia, e-mail: [email protected] ; [email protected]

Here we are considering a possibility of the prospecting hydrothermal zones on the basis of geodynamic analysis of the sea bottom.

Also we present the basics of building deformational models using the finite-element method (FEM) for the sections of the sea bottom formed under the influence of a high-temperature hydrothermal fluid.

IntroductionThe deformational model of DSPS ore objects has been developed with the aim of understanding a

relation between the active hydrothermal zones with stressed sections of the Earth’s crust (the locations of stress, strain and discharge). The deformational model is based of the chart of block structure of the seabed preliminarily drawn using the method of geodynamic zoning. [4]

The block chart of bottom relief was approximated by a two-layer structure; the thickness of the upper, highly plastic one was taken equal to 1/4 of the thickness of the lower, plastic-deformed one. Because of the layered structure of seabed this approach is believed to be sound.

It was supposed that under the weight of the upper layer plastic deformation of the underlying one is tak-ing place. Its extent directly depends on the block levels, taking into account changes in the seabed relief.

Fig 1. Prediction chart showing the areas perspective for hydrothermal activity based on distribution of tangential stresses on the sea bottom relief block structure (the SWIR area).

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The stress distribution in the presented model is calculated using the finite-element method (FEM) which allows approximating a complex relief by the set of great number of elementary areas.

As a result we have the potential energy for every finite element which further allows describing the ac-tive normal and tangential stresses [1, 2, 3, 5].

Problem statement and solutionEarlier we carried out the works in six areas of MAR — the ore nodes Logatchev, Ashadze, Semenov, as

well as at the ore shows 24°30’ and Zenith-Victoria. We have found one regularity: the active hydrothermal centers tend towards zero-line (τtang. = 0), the relict and low-active ones are located in the zones of strain deformation where τtang.< 0. The charts were further compared with morphostructure maps and the maps of elementary surfaces. On this basis we chose sub-horizontal sites located in the zones of discharge. Using the data of lineament analysis and geophysical data we predicted probable hydrothermally active zones.

For further deepening and adjustment of the method for low-speed parts of the spreading we have car-ried out the works in the SWIR (48°—51° E.) area of the Indian Ocean.

The results have confirmed the regularity earlier noticed for MAR, i.e., that the active field (49°30’ E.) [6] is located in the discharge zone and the passive one (50°30’ E.) — in the zone of straining (Fig. 1).

Two maps have been drawn for the SWIR area, one based on the data of the two-minute grid ETOPO-2’, the other — on the basis of the the 30 second grid GEBCO-30’’. In both cases the areas of perspective in our opinion are the same. Finally we have singled out several perspective areas (polygons 1 and 2) where we recommend to search for hydrothermal fields (Fig. 1).

ConclusionsAn obvious correlation between the zones of hydrothermal activity and the discharge zones (τtang.= 0)

and strain (τtang.< 0) is seen in all the zones under study.Thus the suggested method allows defining perspective areas of hydrothermal activity with localization

of the deposits of deep-sea sulfide ore at early stages of exploration, mainly based on the analysis of bathym-etry data [1, 2, 3].

RefeReNCeSPetukhov S.I., Alexsandrov P.A.1. Deformation model of hydrothermal sulfide ore fields, based on the block structure of a host area, abstract Minerals of the ocean -3, 2006, pp. 123-124.Alexsandrov P.A., Anikeeva L.I., Andreev S.I., Petukhov S.I. 2. Thalassochemistry of the ocean ore genesis, editor: Academician RAS S.I. Andreev,Saint Petersburg, 2010,P 274 (in Russia)Petukhov S.I., Alexsandrov P.A.3. Deformation model of hydrothermal sulfide ore field for the Rainbow area, abstract Minerals of the ocean -4, 2008, pp. 70-72.Petukhov I.M., Batygina I.M.4. Geodynamics subsoil. Moscow, Nedra, 1999, pp.1 - 288. (in Russia).Petukhov I.M. 5. Bursting on the coalmine Saint Petersburg, VNIIMI, 2004, P238 (in Russia).Tao 6. C., et al. Inactive Hydrothermal Vent Field Discovered at the Southwest Indian Ridge 50.5°E. www.inter-ridge.org/en/node/5706, 2009

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SedimeNTaTiON HiSTORY Of meTallifeROuS aNd ORe-BeaRiNG SedimeNTS Of THe KRASNOV HYdROTHeRmal field

(16º38’N, maR) fOR THe laST 80 KYR

Rusakov V.Yu.1, Shilov V.V.2, Roshchina I.A.1, Kuzmina T.G.1, Kononkova N.N.1

1 V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKHI), RAS, 19, Kosygin str., Moscow 119991, Russia, e-mail: [email protected] Polar Marine Geological Prospecting Expedition (PMGPE), 24, Pobedy Str., Lomonosov 188512, Russia, e-mail:[email protected]

Discussed material was collected by V.V. Shilov in 28-th cruise on board of R/V Professor Logachev in 2006. For the first time on 16°38’ N, Mid-Atlantic Ridge (MAR), non-active hydrothermal field was revealed by researchers of PMGPE in 24-th cruise on board of the same ship in 2004. This field locates on eastern terrace within rift valley of MAR close to volcanic caldera at the depths between 3600 and 3700 m, and consists of two ore bodies: area of 580×380 m and 110x130 m; height from 1 m to 7 m (fig. 1). Total mass of these bodies is at least 13.9 million tons of ore. Maximal thickness of exposed strata by sediment box cores (40×40 cm) is 127 cm. The strata consist of carbonate metalliferous ooze (carbonaceous metalliferous sedi-ments) and ore-bearing sediments in lower layers (fig. 2).

Lithology and lithostratigraphy. On the basis of lithological, grain-size, and chemical compositions, as well as study of planktonic foraminifera and 230Th dating (Shilov et al., 2009), the sediments can be divided on three units: Unit I consist of Holocene biogenic carbonate ooze with lower contents of ore minerals; Unit II consist of Upper Pleistocene (11—75 kyr BP) biogenic carbonate ooze with higher contents of ore minerals; Unit III consist of Upper Pleistocene (>75 kyr BP) ore-bearing sediments with very low contents of biogenic carbonates or without them.

Chemical composition. It was revealed that the correlation ratios between chemical elements of the sedi-ments within the hydrothermal field are a mixture of hydrothermal-altered alumosilicates (silicates) and ore matter, while the background sediments (28L-50 core, 1.5 n.miles northeastwards) indicates a clear structure genetic fragmentation in the correlation ratios between clay minerals, volcanogenic and edaphogenic miner-als, biogenic carbonates, and ore-minerals as well. It was also shown in our previous work (Rusakov, 2010), that according to potential source, the metalliferous sediments can be divided on two different subfacies: the products of ore-body destruction (proximal facies) and material precipitated from the buoyant and non-buoyant plumes (distal facies). Results of geochemical research of the Krasnov hydrothermal field sediments showed that main source of the ore minerals in the sediments is the products of ore-body destruction, which form the ore-bearing sediments with high contents of Cu and Zn (Cu+Zn > 0.25 wt.% in carbonate-free matter (Beltenev et al., 2006).

Main stages of sedimentation history. Three times of sedimentation were found: active hydrothermal phase (>75 kyr BP), decreased phase (75—11 kyr BP), and non-active phase (last 11 kyr). The most intense phase of hydrothermal activity and accumulating of ore-bearing sediments stopped about 75 kyr BP. Time between 11 and 75 kyr BP indicates gradual decreasing hydrothermal activity. For that time the field reacti-vated short run at least two times. Pelagic biogenic carbonaceous sediments were mainly accumulated during the non-active phase for the last 11 kyr.

RefeReNCeSBeltenev V., Shilov V., Popova Y., Rozhdestvenskaya I1. . Geochemical features of sediments at the hydrothermal fields of MAR 13°N // Materials of International conference: Minerals of the Ocean – 3. Future develop-ments. St.-Petersburg, 2006. P. 28-29.Rusakov V.Yu.2. Possible reasons for correlation between the concentrations of major and trace metals in metal-liferous sediments // Geochemistry International. 2010. V. 48. No. 3. P. 305-314.Shilov V.V., Rusakov V.Yu., Roshchina I.A., Kononkova N.N3. . Lithological and chemical composition of metal-liferous sediments of the Krasnov field (16°38’ N, MAR) / Proceedings of the XVIII international conference on marine geology / Geology of seas and oceans. V. II. Moscow, 2009. P. 206-210.

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87

NeW daTa ON COmPOSiTiON Of Sulfide OReS iN «SemYONOv» ORe CluSTeR

Samovarov M.L., Ivanov V.N., Beltenyov V.Ye., Rozhdestvenskaya I.I.

State Enterprise “Polar Marine Geological Prospecting Expedition”

The main goal of the cruise 32 of R/V “Professor Logatchev” (December 2008—June 2009) was the investigation of the hydrothermal fields of “Semyonov” ore cluster, discovered in 2007 on the Western board of the rift valley, in the region of the mountain 13° 30' N.

The site of prospecting work is situated at he Northern part of the Western board terrace and limited from the North with a big non-tranыform fault which is the boundary of a third order. The main object of re-search was a sea-pick mountain, complicating the terrace surface. It has a sublatitudinal strike and extension of 9,5 km. The height of the mountain over the terrace level is about 700 m. The hilltop surface is crowned with two volcanic structures with excess heights of 50 and 150 m.

The site of works is characterized by wide spreading of deep-sea rocks of the upper mantle and crust complex of unknown age, occupying ca. 60% of the area of bedrock exposures. Exposures of the effusive rocks are correspondingly about 40% from the bedrocks area and represented mainly by aphyric and por-phyry tholeiitic basalts. On the North of the site and on the Nortern slope of the sea-pick mountain, the veined acid rocks and plagiogranites are uplifted.

The first stage represented investigations with geophysical complex AMK “Rift-3” in NF (natural field) modification. The NF anomalies of different intensity were discovered. The most part is stretched along the Northern slope of the mountain 13° 30'N., and in the central part of the mountain, near the Eastern and Western foothills.

The second stage comprised submarine television observations and sampling within the limits of previ-ously discovered hydrothermal fields (Semyonov-1, 2, 3, 4) and on the sites of the revealed anomalies of the natural electric field. As a result, new data were received on the structure of the known fields and a new hydrothermal ore field “Semyonov-5” was discovered.

The hydrothemal ore field “Semyonov-1” is inactive, is situated in the depths interval 2570—2620 m, spatially related to periodotites, has the dimensions 200 × 175 m. It is a single ore hill. The hydrothermal material is picked up on 9 stations. The sulfide ores are represented by the massive and brecciated sulfur-pyrite ores of marcasite-pyrite composition with the relics of the ancient modified pyrrhotite ore fragments and by the variable quantities of melnikovite, barite, opal. Few fragments of copper pipes, mainly of chal-cosine-chalcopyrite composition with variable quantities of isocubanite, secondary non-stoichiometric cop-per sulfides, sphalerite, opal, barite, crusts. The average contents of metals in the ores are: Fe — 38.27%, S — 39.10%, Cu — 4.21%, Zn — 0.22%, Cd — 13 g/ton; Ba — 1.81%, Sn — 20 ppm; Ag — 34.78 ppm, Au — 5.19 ppm, Se — 59 ppm, Te — 4 ppm, Tl — 17 ppm, Ga — 46 ppm.

Hydrothermal ore field “Semyonov-2” is situated at a depth interval of 2360—2580 m and spatially re-lated to basalts. It consists of two ore bodies. The first has the dimensions 600 × 400 m. The second one has the dimensions of 200 × 175 m. The field is active, two zones of contemporary activity with hydrothermal biocenose in the confines of the biggest ore body were defined. Hydrothermal fauna is represented by bi-valved mollusks, gastropoda, crabs, shrimps and other species typical for hydrothermal fauna. In the course of submarine television survey, hydrothermal outcomes were observed. The samples were taken from 14 sta-tions. Sulfide ores were represented by massive copper and copper-zinc ores, fragments of copper and copper-zinc composition and their opalized varieries, ore breccias, streaky ingrained mineralization in the rocks and sulfatized opal-barite formations, crusts. The average concentrations of metals in ores are: Fe — 13,03%, S — 19,77%, Cu — 24,87%, Zn — 4,20%, Cd — 168 ppm, Pb — 290 ppm, Co — 83 ppm, Ba — 0.85%, Sn — 16 ppm, Ag — 185,22 ppm, Au — 18,82 ppm, Se — 564 ppm, Te — 30 ppm, Tl — 4 ppm, Ga — 18 ppm.

Hydrothermal ore field “Semyonov-3” is inactive, related to basalts, has dimensions of 1200 × 650 m. It was tested by one TV bucket grab and one dredge. The sulfide ores are represented by sulfide breccia, massive ores, hydrothermal crusts and streaky ingrained ores in the ricks. The average concentrations of metals in ores are: Fe — 39,32%, S — 36,65%, Cu — 0,22%, Zn — 0,07%, Cd — 9 ppm, Pb — 78 ppm, Co — 96 ppm, Ba — 1,30%, Sn — 24 ppm, Ag — 9,98 ppm, Au — 0,60 ppm, Se — 9 ppm, Te — 3 ppm, Tl — 10 ppm, Ga — 42 ppm.

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Hydrothermal ore field “Semyonov-4” is inactive, spatially related to basalts, 2700 m in latitudinal direction and 1600 m — in meridional one. Samples were taken by 15 TV bucket grab and 3 КП. There are sulfide ores (massive, breccia, pipes), silificated sulfidized basalts, crusts. The average concentrations of metals in ores are: Fe — 41,83%, S — 42,62, Cu — 1,20%, Zn — 0,09%, Cd — 11 ppm, Pb — 1330 ppm, Co — 2470 ppm, Ba — 2,04%, Sn — 13 ppm, Ag — 10,05 ppm, Au — 0,73 ppm, Se — 14 ppm, Te — 3 ppm, Tl — 8 ppm, Ga — 45 ppm.

Hydrothermal ore field “Semyonov-5” is inactive (?). Spatially related with basalts as well as to ser-pentinized peridotites, has the dimensions of 700 x 500 m. Very different hydrothermal material is obtained with a help of two TV grabs and one dredge. The ore material is represented by pyrite fragments of pipes and sulfur ores. The average concentrations of metals in ores are: Fe — 39,55%, S — 38,15%, Cu — 10,61%, Zn — 0,28%, Cd — 17 ppm, Pb — 1330 ppm, Co — 4880 ppm, Ba — 1,04%, Sn — 5 ppm, Ag — 25,95 ppm, Au — 2,26 ppm, Se — 286 ppm, Te — 15 ppm, Tl — 8 ppm, Ga — 40 ppm.

While determining the absolute age ( method U/230 Th) of the sulfide ores samples, the following re-sults were obtained: ores of field “Semyonov-1” are 13—37 Ky old; “Semyonov-2” — 3—75 Ky; “Semyo-nov-3” — 35—51 Ky; “Semyonov-4” — 2—124 Ky; “Semyonov-5” — 8—16 Ky. Thus, large hydrothermal ore formation in this region began no less than 124 thousand years ago and is going on.

The ore cluster “Semyonov” is the biggest accumulation of sulfide ores within the limits of MAR. By the preliminary evaluations, ore resources are evaluated as more, than 40 million tons:

Resourses of sulfides in the ore cluster “Semyonov”

Ore fieldArea of the cal-

culated ore body, (m2)

Thickness of the ore body

(m)

Volume of the ore body

(m3)

Density of the raw ore DPS

(ton/m3)

Density of the dry ore DPS

(ton/m3)

Resources of raw ore mass (ths.t)

Resources of dry ore mass (ths.t)

“Semyonov-1” 56000 5 280000 3.24 2.86 900 800

“Semyonov-2” 92000 5 460000 3.46 3.24 1600 1500

“Semyonov-5” 105000* 5 525000 3.05 2.68 1600 1400

“Semyonov-3” 290000* 5 1450000 3.46 3.09 5000 4500

“Semyonov-4” 1800000* 5 9000000 3.94 3.76 35500 33800

Total in the ore cluster 44600 42000

* The probable resources were calculated for the area equal to half the outline of the ore hills.

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fluid iNCluSiONS daTa ON THe PHYSiCO-CHemiCal PaRameTeRS Of THe ORe-fORmiNG HYdROTHeRmal SYSTemS

aT THe GalaPaGOS RifT (PaCifiC OCeaN)

Simonov V.A.1, Maslennikov V.V.2, Shilova T.V.1, Maslennikova S.P.2

1Institute of Geology and Mineralogy SB RAS, Academician Koptyug ave., 3, 630090, Novosibirsk, Russia, e-mail: [email protected] of Mineralogy UrB RAS, 456317, Miass, Chelyabinsk region, Ilmen Reserve, e-mail: [email protected]

As a result of active researches of the Pacific ocean bottom a variety of hydrothermal fields with sulphide ores was discovered. The majority of these fields is situated at the East Pacific Rise (EPR). To the east from EPR in the subequatorial zone at the Galapagos Rift hydrothermal ores are also characteristic. In this region a large bodies of massive sulphides were found (Malahoff, 1982; Skirrow, Coleman, 1982; Rhona, 1986). With the help of deep-water submersible ALVIN samples of sulphide chimneys were gathered (Emblay et al., 1988; Ridley et al., 1994). Well preserved fragments of chimneys and channels was presented for research by I.R. Jonasson.

Trace element zoning across chimneys was analysed using laser-ablation ICPMS in CODES (Tasmania University). Fluid inclusions in minerals from sulphide chimneys were studied with the help of thermometry and cryometry methods (Ermakov, Dolgov, 1979; Roedder, 1984).

Chalcopyrite-pyrite-sphalerite “black smokers” show distinct mineralogical zonation. The outermost Zone A is composed of colloform pyrite and marcasite. Euhedral and subhedral pyrite crystals are cemented by chalcopyrite in the innermost part of the zone. Zone B is dominated by chalcopyrite with euhedral pyrite and the axial zone C by subhedral crystals of pyrite and sphalerite.

The study has shown systematic trace element distribution patterns across chimneys. Layers of chalcopyrite in the central conduits of the different samples of the chimneys are highly variable in Se (20 —3000 ppm), Ag (20—300 ppm), and Sn (50—250 ppm), but are low in other elements. Euhedral pyrite has elevated Te (up to 273 ppm) and Bi (up to 534 ppm), probably, due to Bi-tellurides in the outer part of chalcopyrite layers. Sphalerite in the conduits contains elevated Pb (up to 2146 ppm). Probably, Pb reside in micro-inclusions of galena. The sphalerite is enriched in Ag (up to 250 ppm).The highest concentrations of trace elements (Ag, Ni, Mn, Co, As) found in colloform pyrite within the outer wall of the chimneys, and likely result from rapid precipitation in high temperature-gradient conditions. This zonation is very similar to studied ones in ancient “black smoker” chimneys from the Urals VHMS deposits (Maslennikov et al., 2009). High Te, Bi, Pb and Ag are also typical of the chimneys from Uralian VHMS deposits but not for chimneys from EPR 9N.

Fluid inclusions were found in the translucent silica, consisting of densely packed micro globules (30—40 microns in diameter). Inclusions (10—30 microns) settle down in regular intervals in silica between micro globules in close association with small sulphide crystals. Two-phase inclusions have forms with concave borders depending on “packing” of globules. Thus, inclusions occupy actually residual space between micro globules, in which solutions, deposited silica on the internal walls of channels, were preserved. According to the external view they are similar to the inclusions, studied by us earlier in the silica from hydrothermal constructions of the «Vienna Wood» in the Manus back arc basin (Pacific Ocean) and from sulphide ores of Menez Gwen hydrothermal field at the Mid-Atlantic Ridge (Simonov et al., 2002, 2006).

Cryometry researches of fluid inclusions in silica from sulphide chimneys of the Galapagos Rift have shown that solutions of inclusions freeze at temperatures from –38°C to –42°C. According to values of eutectic parameters (–25— -26°C) there is a system NaCl-H2O with KCl impurity in solutions. According to melting temperatures of the last ice chips (from –2.1 to –2.8°C), salinity of the trapped solutions was 3.1–4.3 wt.% of NaCl equivalent. On the histogram only one maximum with a range of 3—4 wt. % is allocated, that testifies to obvious prevalence of sea water as a part of the hydrothermal fluid circulating in channels of “black smokers”.

Experiments in the heating stage have established two basic ranges of homogenization temperatures of fluid inclusions: 135—160°С and 170—250°С. There are separate measurements up to 330°С. Taking into account the amendments on pressure, according to depth of sulphide ores disposition at the Galapagos Rift (to 2850 m) (Rhona, 1986), it is possible to estimate real temperatures of silica formation: 170—190°С, 200—280°С and to 350°С.

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On the ratio of solutions salinity and homogenization temperatures the considered fluid inclusions in silica form actually one group (with intervals 2.7—4.8 wt.% and 120—280°С), different on smaller values of parameters from the data on inclusions in anhydrite of typical “black smokers”.

Comparing the obtained data on inclusions in silica from the Galapagos Rift to results of research of similar fluid inclusions in translucent opal like versions of quartz of Menez Gwen hydrothermal field (Mid-Atlantic Ridge) and from sulphide constructions of Manus Basin (western part of Pacific ocean) (Simonov et al., 2002, 2006), we can see both similarity and essential differences. According to the composition of solu-tions and their concentrations inclusions from the Galapagos Rift are most similar to the data on inclusions in minerals from the Manus Basin — prevails NaCl with KCl admixture and the content of salts in solutions is minimum: 1.6—4.2 wt.%. At the same time, homogenization temperatures of inclusions from the Manus Basin are essentially lower — 102—118°С. In the case of the Menez Gwen field the reverse situation is estab-lished: temperatures basically are close (185—265°С and to 350—440°С), but compositions (with possible additive MgCl2) and concentrations (5.0—7.8 and to 18.3—22.5 wt.%.) are different.

During comparison with results of typical “black smokers” researches it is found out that the minimum values of salinity of fluid inclusion solutions (3.5—5 wt.%) in anhydrite from sulphide ores as from low spreading (Logatchev and ТАG fields, Central Atlantic), and high spreading (9° N field, East Pacific Rise) ridges, are close to the data on inclusions in the silica of the Galapagos Rift. At the same time, tempera-tures, and also prevailing values of solution salinity are considerably above during crystallization of sulphide constructions with anhydrite. Thus, the studied fluid inclusions in the silica state, most likely, physical and chemical parameters of last portions of the solutions circulating on channels of sulphide chimneys of the “black smokers” at the Galapagos Rift.

We are grateful to say many thanks to I. Jonasson for excellent samples presented, and also for R. Large and L. Danyushevsky for support in LA-ICPMS analyses, which were carried during a visiting program (2009), funded by the ARC Centre of Excellence grant to CODES, University of Tasmania. The mineralogical researches and fluid inclusions study were supported by Project of UD RAS (N 09 И-5-2004) and Project N 98.

RefeReNCeSEmblay R.W., Jonasson I.R., Perfit M.R., Franklin J.M., Tivey M.A., Malahoff A., Smith M. F., Francis T.J.G1. . Submersible investigation of an extinct hydrothermal system on the Galapagos Ridge: sulphide mounds, stockwork zone and differentiated lavas // Canadian Mineralogists. 1988. V. 26. P. 517-539.Ermakov N.P., Dolgov Yu.A.2. Thermobarogeochemistry. M.: Nedra. 1979. 271 p.Malahoff A. A3. comparison of the massive submarine polymetallic sulfides of the Galapagos Rift with some continental deposits // Mar. Tech. Soc. J. 1982. V. 16. N 3. P. 39-45.Maslennikov V.V., Maslennikova S.P., Large R.R., Danyushevsky L.V.4. Study of Trace Element Zonation in Vent Chimneys from the Silurian Yaman-Kasy Volcanic-Hosted massive Sulfide Deposits (Southern Urals, Russia) Using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) // Economic Geology. 2009. V. 104. P. 1111-1141.Rhona P.5. Hydrothermal mineralization in the oceanic spreading regions. M.: Mir, 1986. 160 p. Ridley W.I., Perfit M.R., Jonasson I.R., Smith M.F. 6. Hydrothermal Alteration in Oceanic Ridge Volcanics - A Detailed Study at the Galapagos Fossil Hydrothermal Field // Geochim. Cosmochim. Acta. 1994. V. 58. Iss. 11. P. 2477-2494.Roedder E.7. Fluid inclusions // Rev. Mineral. Soc. Amer. 1984. V. 12. 644 p.Simonov V.A, Bortnikov N.S., Lisitsyn A.P., Vikentiev I.V., Bogdanov Yu.A.8. Physico-chemical conditions of mineral-forming processes in modern hydrothermal construction “Viennese Wood” (Manus Basin, Pacific ocean) // Metallogeny of ancient and modern oceans - 2002. Formation and development of deposits in ophi-olite zones. Miass: IMin UrB RAS. 2002. P. 61-68.Simonov V.A, Dranichnikova V.V., Maslennikov V.V., Lein A.Yu., Bogdanov Yu.A.9. Fluid inclusions in the quartz of sulphide constructions of the Menez Gwen hydrothermal field (Mid-Atlantic ridge) // Metallogeny of an-cient and modern oceans - 2006. Conditions of ore formation. Miass: IMin UrB RAS. 2006. P. 71-73.Skirrow R., Coleman M.10. Origin of sulphur and geothermometry of hydrothermal sulphides from the Galapagos Rift, 86° W // Nature. 1982. V. 299. P. 142-144.

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HYdROdYNamiCS aNd GeOCHemiSTRY Of HYdROTHeRmal diS-CHaRGe aT 13O N, mid-aTlaNTiC RidGe

Sudarikov S.M.1, Marshak P.A.2, Mikhalchuk N.N.2

1VNIIOkeangeologia, Angliysky prosp., 1, St.Petersburg, 190121, Russia, e-mail: [email protected], 21 Line, St.Petersburg, 199106, Russia

During Russian-French expedition SERPENTINE on board of RV Pourquoipas? at 13°N MAR it was observed the unstable hydrothermal discharge and phase differentiation of high-temperature solutions with high gas content, low pH and varying in space and time mineralization. In previous Russian expeditions high gas content had an effect on low water density in plume waters.

Results of on-board chromatographic analysis gave evidence of high Н2 and СН4 concentrations in fluid composition. This field is situated in ultramafic serpentinized rocks. The serpentinization process according to several alternative schemes produces significant amounts of H2, and CH4.

11 fluid samples have been taken during ROV dives from 4 different vents located at around 4085-4088m depth. All vents exhibit a temperature close to 353°C. During sampling, gas bubbles, coming out of the vent craters, were observed. Fluid formation is controlled by phase separation (presence of bubbles, chlorinity differs from seawater).

The composition of fluids seems to be uniform and homogeneous. According to the ICP analysis we calculated the end-member composition of fluids. Regression line S(SO4)/Mg shows the quality of sampling and analysis (fig. 1).

Obtained results show the high content of Li, Fe, Mn, Sr, Rb in the end-member fluids of this field in compare with other Atlantic fields.

The estimation of fluid’s volume and dissolved metal content seems useful for evaluation of real eco-nomic potential of hydrothermal fields. Yet the only possibility to solve this problem is mathematical model-ing. We produced the physical model of hydrothermal system at 13°N (fig. 2).

Fig. 1. Regression line of S vs. Mg in fluids.

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Fig. 2. The physical model of hydrothermal system at 13°N. rc — radius of the sulfide tube; rк — radius of the supplying con-tour; h — thickness of the filtration zone.

As a consequence of mathematical conversion of equation proposed by E. Romm we can express the discharge of hydrothermal solution by a formula:

= Qπ K g ∆ ρ h2

µ

lnrk

rc

,

where K — permeability, µ — viscosity,Δρ — difference of cold and hot solutions density. We made a calculation for three types of hydrothermal vents found at the field. According to data from

Russian and French expeditions we constructed physical, mathematical, geological models and made veri-fication with the natural object.

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PluTONiC COmPlex Of THe middle-aTlaNTiC RidGe, THe aGe aNd mulTiSTaGe Of iTS fORmaTiON

Shulyatin O.G., Andreev S.I., Beljatsky B.V., Trukhalev A.I

VNIIOkeangeologia, Angliysky prosp., 1, St.Petersburg, 190121, Russia

The mantle and low crust rocks of gabbro-ultrabasite complex are widespread in the axial part of the slow-spreading Middle-Atlantic Ridge between 14°S and 40°N where they compose the large tectonic blocks between young basalts. Crystal rocks are usually represented by significantly transformed species. The multi-stage character of the regressive metamorphism is determined from amphibolic to green-shale phase. Results of the isotopic-geo-chronological studies of gabbro-ultrabasite complex rocks received by different radio-logical methods (including SHRIMP dating of the zircons) show the wide range of the plutonic formations generation from the Cenozoic (Pleistocene) to the Archaean inclusive. The received discrete datings of the absolute age disintegrate on several groups which coincide with the time of planetary tectonic-magmatic events on the land that obviously evidences about the coordinative geodynamic development of the spaces occupied by the continents and now covered by the ocean. The arranged character of the age datings reflects multistage formation of the plutonic complex that was inherited from pre-oceanic epoch of geological devel-opment. At that, the plutonic formations sometimes were accompanied by outpouring of the effusive rocks that is confirmed by the fact of detection of metabasalts and metapicrites which in the age are complemen-tary with the ancient crystal rocks (protocrust).

Fig. 1. Age-probability diagram based on SHRIMP zircon age data (line, 100 zircon grain), and other isotope-dating method (~85 analyses, stacked diagram) and com-

parison with tectono-magmatic activization epoch.

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Section 3Sea Technology

Heinrichs Reter (Aker Wirth GmbH, Germany)

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96

high-reSoluTion Side-Scan mapping of large areaS of The mid-aTlanTic ridge near 3°n uSing a fleeT

of remuS-Type auTonomouS underwaTer vehicleS

Petersen Sven 1, Michael Purcell2, Greg Packard2, Andy Sherrell3, Dorsey Wanless4, Mark Dennett2, Geoff Ekblaw2, Robin Littlefield2, Neil McPhee2, Michael Mulrooney5, Steven Murphy2, and Marcel Rothenbeck1

1 Ifm-Geomar, Kiel, Germany2 WHOI, Woods Hole, USA3 Harbor Branch at Florida Atlantic University4 University of Florida5 Hydroid Inc., Pocassett, USA)

In April 2010 three remus6000 series autonomous underwater vehicles (AUV’s) have been used to si-multaneously map large areas near the Mid-Atlantic Ridge (3°N) axis in water depths ranging from 1000m to 4000m. One vehicle was provided by the Leibniz-Institute for Marine Science, Ifm-Geomar (Kiel, Ger-many) the other two were provided by the Waitt Institute for Discovery (La Jolla, USA) and managed by the Woods Hole Oceanographic Institute (USA).

The REMUS6000 vehicles, manufactured by Hydroid Inc. (USA), are “cigar-shaped” vehicles (4 m long and weighing approx. 900 kg) and consist of a tapered forward section, a cylindrical midsection and a tapered tail section. An internal titanium strongback, which extends through much of the vehicle length, provides the structural integrity and acts as a mounting platform for syntactic foam, equipment housings, various sensors and release mechanisms. The AUV’s can be used in various payload configurations such as multibeam bathymetry, electronic still camera, or subbottom profiler. For these missions the electronic still camera configurations was installed. An edGetech 2200 M dual frequency (120/410 kHz) side scan sonar was used to map the seafloor, but other frequencies are readily available for more options in resolution and range. The 120 kHz side scan transmitter was used for most missions in order to map large areas (increased range) and to be able to fly at higher altitudes (between 70 m and 90 m) above the rough seabed encountered in this area. The maximum slant range was between 600m and 700m on both sides resulting in a swath width of up to 1.2 km. Line spacing ranged from nearly 1000m in flat areas down to 400 m in steep terrain. Side-scan mosaics were generated with a 1m resolution. Selected areas were targeted by the higher resolution 410 kHz transmitter as well as by bottom photographs flying as low as a few meters above the seabed. The ve-hicles navigated autonomously using a combination of inertial navigation (Kearfott T-24 or T-16 INS) and long baseline acoustic navigation by computing their range to two moored acoustic transponders. Working efficiently in this rough topography at speeds above 3 knots was only possible due to the obstacle avoidance capabilities of these AUV’s.

Overall, 50 missions were completed covering 5487 line km with a nominal speed of 3.0 to 3.7 knots. Av-erage time of the vehicles in the water (including descent and ascent) for single missions was nearly 21 hours thanks to the Li-Ion batteries being used. All three vehicles together mapped an area of 2675 km2 in only 24.5 days which can be recalculated to a coverage of 109.2 km2/day or 36.4 km2/day/vehicle. One of the main benefits of these autonomous systems is their ability to maneuver in this steep terrain while still collecting data, something that would not have been possible with towed side scan systems. This, the fast turn-around time, and their reliability show that these systems are a prime choice not only for large scale exploration for hydrothermal activity using chemical and optical sensors but also for regional geological and oceanographic studies.

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developmenT of a Self-propelled miner and Shallow waTer TeST

Sup Hong, Hyung-Woo Kim, Jong-Su Choi, Tae-Kyeong Yeu, Soung-Jae Park, Suk Min Yoon and Chang-Ho Lee

Maritime and Ocean Engineering Research Institute, KORDI171 Jang-dong, Yuseong-gu, Daejeon, Republic of Korea, e-mail: [email protected]

Commercial production of the manganese nodules from 5,000 m water depth confronts with techno-logical problems in high complexity. Materials, structures and machinery components should resist high pressure, chloride-corrosion and abrasion. The core technologies, seafloor vehicle, nodule pick-up device, slurry pumping system, prediction and control of the coupled dynamic behavior, real-time sensing-and-monitoring, total integrated operation etc. are multi-disciplinary and require a high-level fusion in design phase. Deep-seabed mining operation consists of two stages, collecting and lifting, based on total integrated control of the underwater parts and the surface unit. Self-propelled miner, which collects nodules into the buffer, the intermediate storage for steady lifting operation, is the key to the technological feasibility, and should be supported by the position control of the total mining system.

A self-propelled test miner, named MineRoTM, was developed for the purpose of evaluations of mining performance and viability for scale-up. MineRoTM crawls on the seafloor by two tracks and sweeps the nodules from seafloor by nodule pick-up device. Multi-disciplinary design optimization (MDO) was applied for the development of MineRoTM. The weight and size are 10tons in air (5tons in water) and 5m(L)×4m(W)×3m(H), respectively. It is operated electro-hydraulically in real-time via umbilical cable. Software’s for real-time re-mote control, monitoring and database systems were developed as well.

The main parts of MineRoTM are driving system, nodule pick-up device, posture control link system, nodule disposing part, hydraulic power-pack, hydraulic valve assemblage, buoyancy modules, sensors, elec-tric-electronic system and surface control units (see Fig. 1).

By using the buoyancy modules the mean contact pressure was resulted in 5.6 kPa. The pick-up device was developed in form of hybrid type, i.e. combination of water-jet nodule lifter and mechanical conveyor. The clearance between water-jet nozzles and seafloor is controlled by the posture control link system. The main particulars of MineRoTM are given in Table 1.

The navigation in the sea test was conducted by DGPS for the barge and USBL and vehicle sensors for MineRoTM (refer to Table 2).

Sea tests were performed for validation of the integrated performance of MineRoTM and lifting system. The lifting system consists of one 2-stage pump of mixed-type and reinforced flexible hose. The sea tests were conducted in shallow water around 100 m deep in June, 2009. The seafloor was prepared by 49 tons of artificial nodules made of glass spheres (d = 19 mm, m = 10 g/ea). A non DP barge (L = 51 m, B = 19 m) was used instead of DP vessel. Fig. 2 shows the configuration of the sea test.

The performance results obtained from 7 test runs are summarized in Table 3. The data have been acquired by the Real-Time Opera-tion System of MineRoTM and stored in the DB computer automatically. The real-time remote control showed a flawless performance.

Fig. 1. MineRoTM in launching operation.

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T a b l e 1Main particulars of MineRoTM

Specifications

Mining capacity 8.6t/hWeight 10ton(in air), 5ton(in water)Size 5m(L) × 4m(W) × 3m(H)Power 3.3kVA, 135kW(hydraulic), 15kW(electric)Nodule pick-up hybrid (hydraulic+mechanical)Contact pressure 5.6kPa (mean)Thrusters heading controlRTOS PXI embedded controllerUmbilical single modeLARS Launch & Recovery System

T a b l e 2Sensors for navigation

Instrument Update rate Range Accuracy

VesselFusion USBL 1Hz 7,000m ±0.2m(0.5% rms)DSMTM 232 10Hz - H:0.25m, V:0.5mMAHRS 200Hz ±90° 0.03°

Miner

Combatt 5 - 3,000m ±3cmWHN1200 5Hz 0.5~30m ±0.2%TM0075 10Hz 7~56 LPM ±1%AHRS-S305 10Hz 0~360° ±1°

T a b l e 3Summary of the test results of MineRoTM

Mode Item Unit Full scale Shallow water Results

Driving

Speed m/s ~1.0 ~ 0.5 0.3Sinkage mm - ~ 100 -Slip % - ~ 20 6Torque Nm - ~ 9250 3700Roll deg - ~ 10 ±1Pitch deg - ±5 ±1Slip angle deg - - -

Pick-up Efficiency % 80 30 ~ -Pump torque Nm - 300 296

Launch & Recovery

Yaw rate deg - ±90 ±30Acceleration G - ~ 1.0 0.1

Fig. 2. Configuration of the sea test of MineRoTM.

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Some conclusions have been drawn as follow:Performances of • MineRoTM satisfy the design requirements. It was confirmed that the remotely con-trolled, self-propelled miner is conceptually feasible.Sufficient database has been acquired to be applied for design of pilot miner, which will be integrated •with surface unit operation. Learning process has finished one turn, and design experience and operational know-how were •achieved.

Pilot mining test is being planned for water depth of 2,000 m.

referenceSK.S. Min, J.Y. Shim, Sup Hong and J.S. Choi1. (1997), “Conceptual Design of a Hybrid Pick-Up device for Deep Ocean Mining”, Proc. ISOPE OMS-1997, Seoul, Nov. 24-26, pp. 91-94.Sup Hong, J.S. Choi and J.Y. Shim2. (1997), “Kinematic and Sensitivity Analysis of Pick-Up Device of Deep-Sea Manganese Nodule Collector”, Proc. ISOPE OMS-1997, Seoul, Nov. 24-26, pp. 100-104.Sup Hong, J.S. Choi, J.H. Kim and C.K. Yang3. (1999), “Experimental Study on Hydraulic Performance of Hybrid Pick-Up Device of Manganese Nodule Collector”, Proc. ISOPE OMS-1999, Goa, pp. 69-77.Sup Hong, J.S. Choi, J.H. Kim and C.K. Yang4. (2001), “A Note on Design and Operation of Waterjet Nodule Lifter of Manganese Nodule Collector”, Int. J. Offshore and Polar Engineering, Vol. 11, No. 3, pp. 237-239.Sup Hong and J.S. Choi5. (2001), “Experimental Study on Grouser Shape Effects on Trafficability of Extremely Soft Seabed”, Proc. ISOPE OMS-2001, Szczecin, pp. 115-121.Sup Hong, J.S. Choi and C.K. Yang6. (2002), “Experimental Study on Solid-Water Slurry Flow in Vertical Pipe by Using PTV Method”, Proc. ISOPE Conference.J.S. Choi, Sup Hong, H.W. Kim and T.H. Lee7. (2003), “An Experimental Study on Tractive Performance of Tracked Vehicle on Cohesive Soft Soil”, Proc. ISOPE OMS-2003, Tsukuba, pp. 139-143.J.S. Choi, Sup Hong, H.W. Kim, T.K. Yeu and T.H. Lee8. (2005), “Design Evaluation of a Deepsea Manganese Nod-ule Miner Based on Axiomatic Design”, Proc. ISOPE OMS-2005, Changsha, pp. 163-167.J.J. Jung, J.H. Yoo, T.H. Lee, Sup Hong, H.W. Kim and J.S. Choi9. (2005), “Metamodel-based Multidisciplinary Optimization of Ocean Mining Vehicle System”, Proc. ISOPE OMS-2005, Changsha, pp. 157-162.T.K. Yeu, Sup Hong, H.W. Kim and J.S. Choi10. (2005), “Path Tracking Control of Tracked Vehicle on Soft Cohesive Soil”, Proc. ISOPE OMS-2005, Changsha, pp. 168-174.Sup Hong, J. S. Choi, H. W. Kim, T. K. Yeu, S. J. Park, T. H. Lee, J. H. Yoo and J. J. Jung11. (2007), “Development of a Self-Propelled Test Collector for Deep-Seabed Manganese Nodules”, Proc. ISOPE-OMS-2007, Lisbon.T.H. Lee, J.J. Jung, Sup Hong, H.W. Kim and J.S. Choi12. (2007), “Prediction for Motion of Tracked Vehicle Travel-ing on Soft Soil Using Kriging Metamodel”, Int. J. Offshore and Polar Engineering, Vol. 17, No. 2, pp. 132-138.Sup Hong, J.S. Choi, H.W. Kim, M.C. Won, S.C. Shin, J.S. Rhee and H.U. Park13. (2009), “A path tracking control algorithm for underwater mining vehicles”, J. Mechanical Science and Technology, Vol. 23, pp. 2030-2037.T.H. Lee, M.U. Lee, J.S. Choi, H.W. Kim and Sup Hong14. (2009), “Method of Metamodel-based Multidisciplinary Design Optimization for Development of a Test Miner”, Proc. ISOPE OMS-2009, Chennai, pp. 270-275.Sup Hong, H.W. Kim, J.S. Choi, T.K. Yeu, S.J. Park, S.M. Yoon and C.H. Lee15. (2010), “A Self-Propelled Deep-Seabed Miner and Lessons from Shallow Water Tests”, Proc. OMAE-2010, Shanghai, China.

100

FROZEN HEAT: GLOBAL OUTLOOK ON METHANE GAS HYDRATES

Beaudoin Yannick

UNEP/GRID-Arendal, Teaterplassen 3, 4836 Arendal, Norway; e-mail: [email protected], tel. +47 9542 9247

As part of its 2010—2011 Programme of Work, the United Nations Environment Programme via its collaborating center in Norway, UNEP/GRID-Arendal, is undertaking an assessment of the state of the knowledge of methane gas hydrates. Global reservoirs of methane gas have long been the topic of scientific discussion both in the realm of environmental issues such as natural forces of climate change and as a poten-tial energy resource for development. Of particular interest are the volumes of methane locked away in fro-zen molecules known as clathrates or hydrates. Our rapidly evolving scientific knowledge and technological development related to methane gas hydrates makes these formations increasingly prospective to economic development. In addition, global demand for energy continues, and will continue to outpace supply for the foreseeable future, resulting in pressure to expand development activities, with associated concerns about environmental and social impacts. Understanding the intricate links between methane hydrates and 1) their role in natural systems including the global carbon cycle, 2) their sensitivities to climate variations such as global warming, 3) the key drivers (e.g. economic drivers; resource scarcity drivers; geopolitical drivers) asso-ciated with their evaluation as a possible source of natural gas, and 4) the environmental and societal impacts of possible development, are key factors in making good decisions that promote sustainable development.

As policy makers, environmental organizations and private sector interests seek to forward their respec-tive agendas which tend to be weighted towards applied research, there is a clear and imminent need for a an authoritative source of accessible information on various topics related to methane gas hydrates. The 2008 United Nations Environment Programme Annual Report highlighted methane from the Arctic as an emerg-ing challenge with respect to climate change and other environmental issues. Building upon this foundation, the Global Outlook on Methane Gas Hydrates aims to provide a multi-thematic overview of the key aspects of the current methane hydrate debate for both the land-based Arctic deposits and those in the marine envi-ronment. Although based on the latest scientific work produced by leading experts, the style and language are designed for non-experts. This Outlook will span a range of themes that include: the history of gas hydrates science, natural systems, human impacts, exploration and extraction technologies, sustainable economics and resource efficiency and policy perspectives and challenges.

Thematic ScopeThe Global Outlook on Methane Gas Hydrates seeks to provide policy makers, the general public and

the media with a synthesis of aspects of natural, social and applied sciences that relate to this type of natural gas occurrence. With an emphasis on visual media, the Outlook will define global methane gas hydrate oc-currences in their natural settings and examine the implications on communities and society of the potential use of methane gas hydrates as an energy source.

Volume 1 examines the settings and roles of methane gas hydrates in the natural system. It begins (chap-ter 1) with an examination of the history of hydrate science and a basic definition of methane gas hydrates including: molecular, chemical and physical characteristics, occurrence types and their geological settings and a brief overview of the sources of methane that lead to the formation of methane hydrates.

The volume continues (Chapter 2) with a qualitative examination of global methane gas hydrate oc-currences aimed at providing an overview of their global distribution by type and also of the inherent uncer-tainties linked to the published estimates. This section is meant to provide both a sense of scale but also to properly discriminate between the various global methane reservoirs.

Section 4GAS HYDRATES

101

The next section in the volume (Chapter 3) expands on the role of methane gas hydrates in the natural carbon cycle. A more detailed overview of the natural sources of methane (e.g. biogenic and thermogenic) will be provided including a summary of the global methane budget. Various physical processes that regulate natural methane emissions will be examined in addition to a discussion on the time scales of natural varia-tions in gas hydrate occurrences. Examples from the past will be used to illustrate these natural variations and include: negative carbon excursions in the geological past and the role of hydrates in global transition from ice ages to warm periods. Finally, seafloor and terrestrial geomorphological issues will be discussed including slope slides in the marine/lacustrine settings and the reshaping of the ground surface in permafrost settings.

Chapter 4 will discuss chemosynthetic ecosystems that are dependant on near surface methane emis-sions and how these emissions may be linked to deeper methane gas hydrates occurrences. It will present the various biological processes that regulate natural methane emissions in particular in the marine/lacus-trine environment. The sensitivities of the methane consuming ecosystems to natural climate and geological variations will form an integral part of this chapter.

The final section (Chapter 5) of Volume 1 will contain visual models depicting various scenarios of natural global warming and the associated impacts on global methane gas hydrate reservoirs. This is meant to provide a baseline of sensitivity for discussions related to the anthropogenic amplification of climate vari-ability leading to global warming.

Volume 2 changes focus from natural systems to the examination of the human dimensions of methane gas hydrates ranging from key technological aspects related to methane gas hydrates as a potential large scale source of natural gas, to the development of new/sustainable economics models related to potential development, to the various societal and environmental issues surrounding their possible exploitation. The volume begins (Chapter 1) with an ambitious overview of global energy resource efficiency challenges that lead to the key drivers associated with possible methane gas hydrates extraction. These challenges include geopolitical considerations (e.g. regionalization of energy supply), the climate and energy debate, resource scarcity and global growth in energy consumption (i.e. linked to trends in population growth). Models will be used to present scenarios of the impacts (e.g. on global greenhouse gas emissions) of altering the global energy picture towards a more natural gas based economy while integrating and implementing a strategy for decarbonising the global energy system. From a geopolitical perspective, the possible ramifications of the availability of a large scale energy source that is more globally distributed will de discussed. The environmen-tal and social footprint of potential methane gas hydrates will also be examined in comparison to other non-conventional natural gas sources such as shale gas. Resource valuation taking into consideration ecosystem services (i.e. natural capital) will be proposed as a more realistic and holistic methodology when planning for development. Finally, the main headers of a new/sustainable economics-based business model will be developed and provided as a template for possible future resource development.

Chapter 2 details the technological considerations for the exploration side of possible methane gas hy-drates development. An initial definition of the types of methane gas hydrate occurrences that could poten-tially be developed using existing technologies is followed by a synthesis of the methods used to detect and define these occurrences. Examples of actual real world site that have been technically defined will be used for illustration purposes.

Following the examination of exploration and delineation, the next section (Chapter 3) will detail the technologies and challenges linked to the production of natural gas from methane gas hydrates. An investiga-tion of the recovery approaches using adapted conventional technologies will focus on key elements of the production cycle including accessing the reservoir, dissociation techniques and the requirements for achiev-ing long term production. Disassociation techniques for methane gas hydrates include both methods that can make us of existing technology (e.g. pressure reduction) and those that require additional research and development (e.g. temperature, chemical and mechanical stimulation; CO2 injection; kinetic inhibitors). Unique technical challenges linked to production include the management of water as a bi-product, sand production and gas leakage. This section will then address the broader environmental impacts of methane gas hydrates development based on various scenarios. Examples of impacts include: possible methane release to the atmosphere and/or hydrosphere; possible impacts on methane-based ecosystems; marine slope stabil-ity; impacts on surface morphology (i.e. in permafrost settings).

The following section (Chapter 4) addresses societal perspectives related to energy resource develop-ment. As resource development impacts society from the national to local community scale, this section seeks to illustrate various perceptions linked to energy resource development in order to help shape policies relating to potential future methane gas hydrate development. Areas with previous experience with conventional oil

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and gas development will provide guidance with respect to concerns related to development, the benefits on well-being of development and practical suggestions to improve the polices linked to potential future devel-opment. As occurrences of methane gas hydrates are more globally distributed, many areas with no previous experience with traditional oil and gas development may be affected by methane gas hydrates development. The advice provided in this section will be aimed at ensuring that these previously unaffected areas take into consideration the experiences of others. Case studies from areas including the Arctic region (local commu-nity scale) and countries like Japan and India (national scale having not experienced large scale traditional oil and gas development) will be used to illustrate different realities linked to energy resource development.

The final section of volume 2 (Chapter 5) will seek to summarize the main points emphasized in the entire Outlook into the context of sound policy making. Challenges, opportunities, policy responses and options will be provided for stakeholders from government, the private sector, community leaders and the general public in a broad wrap up of the key messages and discussions contained in the Outlook. This section will also examine past experiences in relation to policy issues and how these can be improved upon to shift away from unsustainable practices in global energy resource use towards the most sustainable development possible of non-renewable, finite resources. A development model for methane gas hydrates based on the conversion of financial revenue to new forms of capital (e.g. social capital in the form of national wealth sharing funds; natural capital in the form of revenue diversion towards the longer term need to develop re-newable energy sources to replace exhausted hydrocarbon reserves) will be expanded upon to provide both government and industry leaders with new management and policy options.

UNEP/GRID-Arendal’s mission is to provide environmental information, communications and capac-ity building services for information management and assessment. Established to strengthen the United Nations through its Environment Programme (UNEP), our focus is to make credible, science-based knowledge under-standable to the public and to decision-makers to promote sustainable development. We are dedicated to making a difference by exploring how environmental information impacts on decision-making and the environment. We seek to bridge the gap between science and politics.

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MODELiNG cOMpOSiTiON OF MixED H2-cH4 HYDRATES OF cUBic STRUcTURE i AND ii AT EqUiLiBRiUM wiTH GAS pHASE

Belosludov Vladimir 1, Subbotin Oleg1, Belosludov Rodion2, Hiroshi Mizuseki2, Yoshiyuki Kawazoe2

1 Nikolaev Institute of Inorganic Chemistry, SB RAS, Siberian Branch of Russian Academy of Science Lavretiev av. 3, Novosibirsk, 630090, Russia,2 Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai, 980-8577, JAPAN

A model has been developed permitting to accurately predict on molecular level phase diagram of the clathrate hydrates. This model allows taking into account the influence of guest molecules on the host lattice (non-rigid host lattice) and guest-guest interaction — especially when more than one guest molecule occupies a cage significantly improves known van der Waals and Platteeu theory. The theoretical study of phase equilibrium in gas–hydrate–ice Ih system for methane and hydrogen hydrates has been performed. The obtained results are in a good agreement with experimental data.

The proposed theory has been used for construction phase P, T - diagrams of mixed clathrate hydrates. On the molecular level the curves of monovariant equilibrium of in gas phase–gas hydrate-ice Ih and the degree of filling of the large and small cavities for mixed CH

4+H

2 hydrates sI and sII in a wide range of pres-

sure and temperature have been determined.It is shown that at divariant equilibrium ‘gas phase — gas hydrate’ with increasing pressure the fill-

ing of large cavities by hydrogen proceeds gradually from single filling to the four hydrogen molecules in clusters included in large cages preserving stability of the hydrates.

Tuning hydrate composition, for mixed hydrates of H2 + CH

4, becomes possible by mean of variation

of CH4 concentration in the gas phase in the interval 0—1%. In this interval of concentrations not all large

and small cages are filled by CH4 molecules that allows the hydrogen guest molecules to enter both large and

small cages.For the mixed hydrogen + methane sI hydrates it was demonstrated that thermodynamic stability de-

pends on the filling degree of small cavities by methane molecules and stability area shifts to lower pressure with increasing filling.

It was found that the largest values of hydrogen mass wt% can be achieved for CS-I structure mixed H2-

CH4 hydrate.This work has been supported by New Energy and Industrial Technology Development Organization

(NEDO) under “Advanced Fundamental Research Project on Hydrogen Storage Materials” and the Rus-sian Fund for Basic Research through Grant No.08-03-00191.

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GAS HYDRATE iNvESTiGATiON OFFSHORE SOUTHwESTERN TAiwAN: AN OvERviEw

Char-Shine Liu1, Saulwood Lin1, Yunshuen Wang2, San-Hsiung Chung2 and Song-Chuen Chen2

1 Institute of Oceanography, National Taiwan University, P. O. Box 23-13, Taipei, 106 Taiwan, e-mail: [email protected], [email protected] Central Geological Survey, MOEA, Taiwan

The area offshore southwestern Taiwan is the place where the Luzon subduction system impinges onto the passive China continental margin. Widespread bottom simulating reflectors (BSRs) have been observed on the seismic profiles which indicate wide distribution of gas hydrate beneath the sea floor. In order to investigate the potential of gas hydrate accumulation in the area, the Central Geological Survey of Taiwan started a 4-year multidisciplinary gas hydrate investigation program in 2004. Marine geological, geophysi-cal, and geochemical investigations have been carried out in the area offshore southwestern Taiwan. The objectives were to map the regional gas hydrate distribution in the investigation area and to understand the geological, geophysical, and geochemical characteristics of the gas hydrates in the region.

The BSR distribution map complied from multichannel seismic data suggests that gas hydrates are pres-ent in an area over 10000 km2 offshore of southwestern Taiwan (Fig. 1), extending from the passive margin of the China continental slope to the submarine Taiwan accretionary wedge, from water depth of 600 to over 3000 m (Liu et al., 2006). Velocity structures derived from pre-stack depth migration and from analyz-ing the wide-angle reflection and refraction data collected by the ocean bottom seismometer (OBS) reveal that low velocity zones exist underneath BSRs, indicating there are free gases within the sediment below the gas hydrate bearing layers (Schnurle et al., 2004). The distribution map of fluid activities identified by chirp

Fig. 1. BSR distribution map offshore southwest Taiwan. Locations of the BSRs as observed on the seismic pro-files are shown as think lines in color. Different colors indicate the depths of BSRs below seafloor. The curved line with teeth is the location of the deformation front which separates the passive China continental margin province west of the deformation front from the accretionary wedge province east of the deformation front. Class A BSR means the BSR is clearly identified on the seismic profiles, and Class B BSR means referred BSR (from amplitude anomalies) or BSR is parallel to the sediment strata.

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sonar data indicate that submarine mud volcanoes and gassy sediments are widely distributed on both the accretionary wedge and the passive continental margin provinces (Chiu et al., 2006).

Near 200 piston and gravity cores have been collected in the study area during the 4-year investigation period. Results from geochemical analyses reveal extremely high methane concentration (Chuang et al., 2006), very shallow sulfate/methane interface (Lin et al., 2006), and common occurrence of authigenic pyrite (Huang et al., 2006) at many coring sites of the investigation area. Anaerobic methane oxidation is indicated by sulfate and methane depletion, hydrogen sulfide formation and an increase in alkalinity in the sediments. The deep-towed camera images illustrate fluids/gases venting from structures, chemosynthetic communities, and widespread authigenic carbonate on the seafloor (Fig. 2). These features indicate that ac-tive fluids/gases vents have developed in the survey area.

The Central Geological Survey started the second phase of the gas hydrate investigation program in 2008, scheduled to last for another four years. In this phase, gas hydrate prospects have been selected for intensive high-resolution surveys which include pseudo 3-D MCS and OBS surveys, dense heat flow measurements, swath bathymetry mapping, controlled source electromagnetic survey, deep-towed side-scan sonar and chirp sonar surveys, deep-towed camera images, as well as ROV observations and sampling. More seafloor sedi-ments, water column samples, chemosynthetic communities, and carbonate crusts at the selected prospects have been collected and analyzed. 18 drill sites were selected from 13 potential prospects in 2008, and a gas hydrate drilling proposal was submitted to the Ministry of Economic Affairs of Taiwan to seek funds for a drilling expedition. This proposal has not been funded yet. A large-offset MCS reflection combined with OBS surveys were carried out in spring 2009 using the R/V Marcus Langseth to investigate the deep structur-al framework and seismic characters of the hydrate-bearing strata in the area offshore southwestern Taiwan. A giant piston coring cruise using the R/V Marion Dufresne is to be conducted in June 2010 to retrieve cored sediments up to 60 m. A gas hydrate database and information system has also been established to preserve the vast amount of data collected, and to facilitate their usages. In addition to the field investigations, ther-modynamic and kinetics of gas hydrate nucleation, growth, and decomposition has been and will continue to be simulated and modeled to provide insights into gas hydrate production technology.

Fig. 2. Authigenic carbonate and chimney structures photoed by the TowCam (deep-towed camera) system. Red arrows point to the small chimney structures on the seafloor.

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The area offshore southwestern Taiwan provides a unique opportunity to investigate characteristics of gas hydrate in both passive continental margin and active accretionary wedge settings. The multidisciplinary gas hydrate investigation program conducted in Taiwan aims (1) to understand the spatial variations of BSR distribution and its relation to the local structures; (2) to investigate the gas origin, its transport mechanisms and migration pathways, as well as its incorporation in gas hydrate; (3) to provide details of the reservoir structure, sediment stratigraphy and gas hydrate occurrence; (4) to develop a “gas hydrate” petroleum sys-tem model; and (5) to estimate the amount of gas hydrate and/or free gas in the sedimentary strata. The results of the Taiwan gas hydrate program will be integrated and used to asses the possibility of future gas hydrate exploration and exploitation offshore southwestern Taiwan.

REFERENcESChiu, J. K., W. H. Tseng and C.-S. Liu, 1. 2006: Distribution of gassy sediments and mud volcanoes offshore south-western Taiwan. Terr. Atmos. Ocean. Sci., 17, 703-722.Chuang, P. C., T. F. Yang, S. Lin, H. F. Lee, T. F. Lan, W.L. Hong, C.-S. Liu, J. C. Chen and Y. Wang, 2. 2006: Ex-tremely high methane concentration in bottom water and cored sediments from offshore southwestern Taiwan. Terr. Atmos. Ocean. Sci., 17, 903-920.Lin, S., W. C. Hsieh, Y. C. Lim, T. F. Yang, C.-S. Liu and Y. Wang, 3. 2006: Methane migration and its Influence on sulfate reduction in the Good Weather Ridge region, South China Sea continental margin sediments. Terr. Atmos. Ocean. Sci., 17, 883-902.Liu, C.S., P. Schnurle, Y. Wang, S.H. Chung, S.C. Chen and T.H. Hsiuan, 4. 2006: Distribution and characteristics of gas hydrate offshore southwestern Taiwan. Terr. Atmos. Ocean. Sci., 17, 615-644.Horng, C. S. and K. H. Chen,5. 2006: Complicate magnetic mineral assemblages in marine sedments offshore of southwestern Taiwan: possible influence of methane flux on the early diagenetic process. Terr. Atmos. Ocean. Sci., 17, 1009-1026.Huang, C. Y., C. W. Chien, M. Zhao, H. C. Li and Y. Iizuka,6. 2006: Geological study of active cold seeps in the syn-collision accretionary prism Kaoping slope off SW Taiwan. Terr. Atmos. Ocean. Sci., 17, 679-702.Schnurle, P., 7. C.-S. Liu, T.-H. Hsiuan, and T.-K. Wang, 2004, Characteristics of gas hydrate and free gas offshore southwestern Taiwan from a combined MCS/OBS data analysis, Marine Geophysical Research, 25, 157-180.

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iNvESTiGATiON OF GAS HYDRATE FORMATiON iN FROZEN AND THAwiNG GAS SATURATED SEDiMENTS

Chuvilin Evgeny M., Lupachik Maria

Geology faculty, Moscow State University, Moscow, Russia, e-mail: [email protected]

The feature of permafrost sediments is capability to accumulate considerable quantity of natural gases mainly methane with low admixture of carbon dioxide. Formation of favorable thermo-baric conditions for transformation of intra-permafrost gas accumulations into gas hydrate is possible due to natural and climatic changes.

By consideration of high gas-saturation of the frozen sediments the active processes of hydrate for-mation in permafrost during the transgression of Arctic seas under conditions of relict submarine perma-frost formation can be expected. Due to sea transgression the pressure over underlying frozen sediments increases inducing the processes of hydrate formation in submarine conditions and leadinh to expansion of gas hydrate stability zone. As a result, gas-saturated frozen rocks imbedded in comparatively low depth get into gas hydrate stability zone and, therefore, intra-permafrost free gas accumulations transfer into gas hydrates.

According to geological and temperature modeling of seabed conditions of Arctic seas, solid subma-rine permafrost on the shelfs of the northern seas can occur up to isobaths of 50-60 meters and its thick-ness can reach 200—300 m. Thus, processes of natural hydrate formation under negative temperatures in permafrost zone can be distributed widely that is necessary to take into account during development of Arctic regions.

Taking into account insufficient knowledge of hydrate formation processes in frozen and thawing rocks, special experimental technology was developed aimed on physical modeling of hydrate formation conditions in cryogenic rocks. Special experimental installation was used providing the modeling of assumed thermo-baric conditions under the wide range of temperatures and pressures. This consists of pressure chamber, thermostat, devices transforming of transmitted electric signal into digital, computer and automatic system of temperature and pressure registration.

During the experimental investigations mechanisms and patterns of gas hydrate accumulation in porous media in cooling, frozen and thawing dispersed rocks (in the range temperatures from -8 to +4 °С and gas pressure up to 8 MPa) were studied. Influence of different factors on the dynamics of gas hydrate accumula-tion in cryogenic rocks was considered.

The aim of the investigation was modeling using original sandy grounds and sandy-loam samples ob-tained in permafrost regions. For the samples preparation the grounds of disturbed structure were used and degree of ice filling of pores from 29 to 80% was provided. The experiments were carried out under constant negative temperatures ranging from -2°C to -8°C. The hydrate-forming gases were methane and CO

2. Analy-

sis of thermo-baric condition change in pressure chamber during process of hydrate formation allows to de-termine characteristics of phase transition in ground samples and also to evaluate quantitative part of porous water (Kh) which turned into hydrate state and to calculate hydrate-saturation of ground samples (Sh).

During the experiments it was determined that accumulation of gas hydrates (methane and СО2) in

porous media runs actively both under positive and negative temperatures (Chuvilin and Gureyva, 2009). In sandy-loam samples under the reduction of the temperature from +2 to -8 oC the rate of gas hydrate forma-tion during initial 10 hours of experiment decreases in 1.5 times (Fig. 1).

However, in spite of decrease of the hydrate formation intensity under reduce of temperature during initial period of time, further decrease of the hydrate formation rate under negative temperatures takes place more slowly that resulted in little differences in hydrate accumulation process.

The experimental data show that after attenuation of hydrate formation in frozen sediments the consid-erable intensification of hydrate accumulation processes can occur during the thawing of residual pore ice, which does not turn into hydrate (Fig. 2). Probably this is connected with thawing of porous ice accompany-ing with its structural-textural changes that is resulted in appearance of new gas-water contacts. As a result there is secondary hydrate formation on the background of thawing of ice.

During the experiments it was determined that intensity of hydrate accumulation depends on degree of ice filling of pores, which defines a surface of ice-gas contact. It was experimentally shown that maximum hydrate-saturation of porous media occurs at optimum value of ice-saturation (Fig. 3). The most favorable

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degree of ice pores filling is in range of 45-65%. If value of ice-saturation is higher, hydrate formation reduces in consequence of gas-ice surface decrease.

Thus, experimental results shows those active processes of hydrate accumulation which can take place in porous media of frozen and thawing gas saturated grounds under thermo-baric conditions of hydrate for-mation. Due to long existence of relict frozen strata on the shelves of the Arctic seas considerable accumula-tion of gas hydrates in frozen and cooling intervals of rocks these shelves is possible.

REFERENcESChuvilin E.M., Gureyva O.M. Experimental investigation of CO2 gas hydrate formation in porous media of frozen and freezing sediments. Earth Cryosphere Journal, 2009, vol. XIII, № 3, p. 70-79 (in Russian).

Fig. 1. Influence of temperature on the rate of CH

4 hydrate formation in sandy-

loam sample (W = 14%) during initial 10 hours of experiment.

Fig. 2. Kinetics of СН4 hydrate accumu-

lation in sandy-loam sample Si = 0.66 (W = 23%) at the constant temperature -3°С and during temperature increase from -3 to +4.1°С.

Fig. 3. Influence of initial ice-satura-tion (Si) on methane hydrate accu-mulation (Sh) in sandy-loam samples under temperature of -2.9°С.

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BREAKUp OF DEEp-wATER METHANE BUBBLES AND GAS HYDRATE FORMATiON

Egorov A.V1, R.I. Nigmatulin1, N.A. Rimskii-Korsakov1, A.N. Rozhkov1,2, A.M. Sagalevich1, E.S. Chernjaev1

1 P.P. Shirshov Institute of Oceanology RAS2 A. Ishlinsky Institute for Problems in Mechanics RAS, [email protected]

During the Russian Academy of Sciences «MIRI na Baikale 2008-2009» expedition, deep-water experi-ments on methane bubbles emerging from the lake bottom at depths of 1400 and 860 meters were carried out. Bubbles escaping the seabed were caught by a trap, which was an inverted transparent glass of diameter of 100 mm. Entering in the trap, bubbles became covered by a gas hydrate envelope and then after a time period collapsed into a number of gas hydrate solid fragments. Due to positive buoyancy, fragments remained in the top part of a trap, exhibiting properties of a powder. The glass’s bottom was replaced with a 1 mm mesh grid, allowing the finest gas hydrate particles to sift through the grid, rising upwards. It is proposed that bubble col-lapse into fragments is related to the pressure drop in the bubble in the course of formation of the gas hydrate envelope. No visible changes in the gas hydrate powder were observed in the course of lifting it to a depth of 380 meters. Shallower than 380 meters, i.e. outside the zone of gas hydrate stability, decomposition of the gas hydrate powder into methane gas was observed.

Pictures show consecutive stages of transformation of the methane bubbles in gas hydrate sand and re-verse process. Data are received with the use of submarine “Mir” on lake Baikal. 1 — the capture of gas bub-bles by means of a trap. The captured bubbles remain within several minutes, depth 860 m. 2 — in 12 minutes bubbles were transformed in gas hydrate sand. 3 — the beginning of process of gas hydrate decomposition at submarine lifting on depth of 380 m. 4 — 84 seconds after beginning of decomposition, depth 327 m.

Work is supported by Federal Program «The World Ocean» (the project 0013), Program of basic research № 17 of the Russian Academy of Sciences and Foundation of Assistance to Preservation of Lake Baikal.

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DEcOMpOSiTiON OF GAS HYDRATES iN BOTTOM SEDiMENTS OF LAKE BAiKAL: pOSSiBLE cAUSES AND cONSEqUENcES

Granin N.G.1, Suetnova E.I.2, Granina L.Z.1

1 The Limnological Institute of SD RAS, Ulanbatorskaya st. 3, Irkutsk, 664033, Russia, e-mail: [email protected] Institute of the Earth Physics by O.Yu. Schmidt of RAS, Russia

Gas hydrates are known in the areas of permafrost, in many oceans and seas. They are considered as possible new source of hydrocarbon fuel. Lake Baikal is the only fresh water body, in which gas hydrates were found in the bottom sediments. The very first travelers who visited Lake Baikal in the 18th century have already pointed out the gas escapes from the bottom. The evidences indicated the presence of gas hydrates in Baikal sediments were firstly found in 1978 (Efremova et al., 1980). Discovery of BSR (Bottom Simulated Reflector) and later on, the gas hydrates themselves (Kuzmin et al, 1998) in Baikal sediments, gave a new impulse to the prospecting works aimed to search for gas and oil escapes in the lake. In accordance with BSR distribution in the sediments and with the interpretation of seismic data, gas hydrates are distributed in two provinces of the lake, located symmetrically about the Selenga River delta. The thickness of gas hydrate layer is estimated to be 34 to 450 meters and, 260 meters on average (Golmshtok et al., 2000). It should be noted that gas escapes were registered also outside the area characterized by BSR existence (Granin et al., 2010). For the gas hydrates stability the temperature and pressure (PT) conditions should be complied in the sediments and there should be enough gas (in free or dissolved form) available to provide the thermodynamic equilibrium between hydrate and pore fluid as well. If these conditions are not met, the gas hydrates decompose.

Gas hydrates may decompose at the lower boundary of their stability due to process of sedimentation. One can estimate the volume of gas evolved because of this process. The lower boundary of gas hydrates sta-bility in Southern Lake Baikal is located at the intersection of temperature profile in bottom sediments (TG) and the curve (Teq), which describes the boundary of thermobaric stability of the gas hydrates in presence of pore fluid (Fig. 1). Various authors have determined the gas reserves in Baikal gas hydrates, taking in their calculations the porosity of sediments to be 50% (Golubev, 2000) or 56% (Vanneste et al., 2001) and assum-ing that gas hydrates occupy from 5 to 10% of pore volume. These starting data we used when assessing the volume of gas released as a result of gas hydrates decomposition due to process of sedimentation.

According to published data (Granina et al., 2004), the characteristic sedimentation rate in Baikal is about 0.65 mm/year in the southern and 0.24 mm/year in the central lake basins; near the Selenga River delta it is around 0.8 mm/year. Based on these sedimentation rates and taking into account that destruc-tion of one volume of gas hydrate under normal conditions produces 164 volumes of gas, we can estimate the amount of methane resulted from decomposition of gas hydrates. It is 5300 m3/(km2 year) in Southern Lake Baikal, 2000 m3/(km2 year) in Central Lake Baikal, and 6500 m3/(km2 year) in the area adjacent to the Selenga River delta.

Changes in both lake level and bottom temperature should also lead to displacement of the boundary of gas hydrates stability in the sediments, and this is conducive to the hydrates

Fig. 1 A phase diagram of the gas hydrates stabil-ity in Southern Lake Baikal, Tw — water tem-perature, for other designations see the text.

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destruction or production. However, temperature fluctuations in the bottom waters may not be significant in the deepwater part of the lake (Schmid et al., 2008), so we neglect this factor. As to changes in the lake level, they certainly contribute to decomposition or production of hydrates. There were periods in Baikal history, when the lake level was changing, which should lead to displacement of the boundary of gas hydrates stability in the sediments. Such periods are exemplified by Fig. 2 that shows the changes of water level in Lake Baikal since the mid of the 20th century.

Displacement of the lower boundary of the zone of gas hydrates stability (Δ H) caused by the changed water level is described by the following expression

l

1

∆∆ =

−

hH'G

'eq

TT

where lh∆ — change in the lake level, 'GT — geothermal temperature gradient, = eqdT

dH'eqT — derivative of

the temperature of gas hydrates stability along the depth. Geothermal temperature gradients typically range

in Baikal 60 to 100 mK m-1 (Golubev, 1997); they significantly exceed the gradient of equilibrium tempera-

ture of gas hydrates. In such a case lh∆ ≈ ∆H

'eq

'G

TT

A simple calculation shows that about 1 m change in the lake level caused by construction of the Irkutsk hydropower station has resulted in changed pore pressure and, correspondingly, in displacement of the lower boundary of gas hydrates stability zone by about 5 cm. When the lake level is lowering for a long time, the escaping gas may accumulate under the newly established boundary of the hydrate layer. Volume of this gas depends on the amount of hydrates, which used to exist within the sediments before the level has changed. Under sediment porosity and amount of hydrates typical of Baikal (see above), 1 m lowering of the lake level would result in gas release of 4100 m3 per km2. However, the chance of this gas to reach the sediment surface depends on the permeability of sediments, initial pore pressure existed in the sediments before the level fall, and the methane concentration in pore fluid as well. Simulation of the process of hydrates decomposition due to lowering of the reservoir level showed that this process results in the increased strata pressure below the boundary of hydrates stability zone (Xu, Germanovich, 2006).

The hypothesis that intensity of the bottom gas escapes into Baikal water column is related to fluctua-tions of the lake level has indirect evidence. It is known that in the 18-20th centuries, there was mass death of the deep-water endemic oilfish golomyanka (Comephoridae) in Lake Baikal. As far back as in the 19th century, one of the early Baikal investigators A.L. Chekanovsky suggested that this phenomena could be re-lated to the gas escapes from the bottom (Granin, Granina, 2002). If such a relationship actually existed, the disappearance of this phenomenon since the 1960s of the 20th century may indicate a decreased intensity of gas escapes from the bottom. Stopping of the mass death of golomyanka is probably the consequence of the lake level raising after construction of the Irkutsk hydropower station in 1958, since rise of the level should result in deepening of the lower boundary of gas hydrates existence by about 5 cm. Increased external pres-sure acts as a stabilizing factor and leads to additional formation of gas hydrates in the sediments; therefore it may reduce the gas input into the water.

The methane escape caused by the gas hy-drates decomposition may significantly affect the climate and contribute to a serious restruc-turing of the ecosystems, including speciation (Kemp et al., 2005). During the glacial periods in the Baikal region, there were considerable drops of the lake level, as evidenced by the regional climate reconstructions (Goldberg et al., 2005). In the early isotopic stage MIS4 (70-90 thousand years ago), the level drop was

Fig. 2 Fluctuationsof average annual water levels of Lake Baikal (Sinyukovich, 2005).

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about 30 meters (Urabe et al., 2004). According to our calculations, it was accompanied by 1-2 meters rise of the lower boundary of hydrates stability, which should, after a certain period of time, provoke significant emissions of methane. Estimates based on the paleotemperature regime of sediments and velocity of gas filtration within the sediments (which ranges 0.5 to 0.05 m / year, depending on the sediments permeabil-ity), show that this time interval is about one hundred years. The results of molecular-biological studies indicate that at a time close to the catastrophic drop of the lake level (39-109 thousand years ago), a new fish species — small golomyanka — has been created in Baikal (Teterina et al., 2010). Perhaps it was due to significant the methane release from bottom sediments caused by the lake level lowering during this period. Some earlier, endemic species of the largest freshwater diatoms have appeared in the lake: Cyclotella bai-kalensis (146 thousand years ago) and Aulacoseira baicalensis (122 thousand years ago) (Khursevich et al., 2001). Probably, their appearance is related to the beginning of intensification of the methane escapes from the sediments caused by BSR formation and accumulation of gas hydrates near the lower boundary of their existence.

ConclusionIn the lake areas, characterized by BSR and the gas hydrates existence, the methane hydrates are decom-1. posed during sedimentation. At this, if there is low permeability of sediments, abnormally high pore or strata pressure can be generated, leading to formation of mud volcanoes and the methane escapes from the bottom. The volume of methane escaping due to sedimentation should be taken into account when estimating the methane balance in the atmosphere.The volume of methane resulted from the gas hydrates decomposition is controlled by amount of gas hy-2. drates at the lower boundary of their stability. The estimates indicate that destruction of hydrates due to sedimentation may annually produce in some lake areas up to 6500 m3/km2 methane. Changes in the lake level significantly affect the methane escape from the sediments. It is estimated that 3. 1 m lowering of the lake level can trigger release of 4100 m3/km2 methane. Happened in the past lowering of the lake level could lead to significantly increased methane escapes from the bottom, which may have contributed to speciation.

This work was supported by RFBR grants 08-05-98091, 10-05-01094а, by interdisciplinary integration SD RAS projects № 20 and № 23 and project of Prezidium RAS 20.10.

REFERENcESGolubev V.A.1. Geothermal forecast of the depths of lower boundary of the gas hydrate layer in sediments of Lake Baikal // Doklady of Academy of Science, 1997, v. 352, № 5, p. 625-655 (in Russian).Golubev V.A.2. Geothermal forecast of the gas hydrate reserves in the sediments of Lake Baikal // Abstracts of all-Russian scientific conference “Geology and petroleum potential of the Western Siberian megabasin”. Tyumen, 2000, p. 14-17 (in Russian). Goldberg E.L., Chebykin E.P., Vorob’eva S.S., Grachev M.A.3. Uranium signal of paleoclimates humidity in the sediments of Lake Baikal // Doklady of Academy of Science, 2005, v. 400, № 1, p. 72-77 (in Russian).Granin N.G., Granina L.Z. 4. Gas hydrates and gas escapes in Lake Baikal // Russian Geology and Geophysics, 2002, v. 43, № 7, p. 625-633 (in Russian).Efremova A.G., Andreeva M.V., Levshenko T.V. etc.5. On the gases in the Baikal sediments // Geology and explora-tion of gas and gas condensate fields, 1980, v. 2, p. 15-23 (in Russian).Kuzmin M.I., Kalmychkov G.V., Geletei V.F., etc.6. First record of gas hydrate in the sediment of Lake Baikal // Doklady of Academy of Science, 1998, v. 362, № 5, p. 141-143 (in Russian).Sinyukovich V.N7. . Reconstruction of the natural level of Lake Baikal after construction of the Irkutsk hydropower station // Hydrology and Meteorology, 2005, № 7, p. 70-76 (in Russian).Khursevich G.K., Karabanov E.B., Prokopenko A.A. et al.8. Detailed diatom stratigraphy of the sediments in Lake Baikal in the Brunhes age and climatic factors of speciation // Geology and Geophysics, 2001, v. 42, № 1-2, p. 108-130 (in Russian).Golmshtok A.Y., Duchkov A.D., Hutchinson D.R., Khanukaev S.B. 9. Heat flow and gas hydrates of the Baikal Rift Zone // International Journal of Earth Sciences, 2000, v. 89, Issue 2, p. 193-211.Granin N.G., Makarov M.M., Kucher K.M., Gnatovsky R.Yu. 10. Gas seeps in Lake Baikal — detection, distribution, and implications for the water column mixing // Geo-Marine Letters. 2010. DOI10.1007/s00367-010-0201-3.Granina L., Muller B., Wehrli B.11. Origin and dynamics of Fe and Mn sedimentary layers in Lake Baikal // Chemi-cal Geology, 2004, v. 205, p. 55-72.

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Kemp D.B., Coe A.L., Cohen A.S., Schwark L.12. Astronomical pacing of methane release in the Early Jurassic pe-riod // Nature, 2005, v. 437, p. 396-399 | doi:10.1038/nature 04037.Schmid M., Budnev N.M., Granin N.G. et al.13. Lake Baikal deepwater renewal mystery solved // Geophys. Research Letters, 2008, v. 35(L09605), p. 1-5.Teterina V.I, Sukhanova L.V, Kirilchik S.V. 14. Molecular divergence and sympatric speciation of Baikal oilfish (Come-phoridae): facts and hypotheses // Molecular Phylogenetics and Evolution. 2010, in press.Xu W., Germanovich L.N.15. Excess pore pressure resulting from methane hydrate dissociation in marine sediments: A theoretical approach // J. Geoph. Res., 2006, v. 111, B01104, doi: 10.1029/2004JB003600, 2006, p. 1-12.Vanneste M., De Batist M., Golmshtok A. et al.16. Multi-frequency seismic study of gas-bearing sediments in Lake Baikal, Siberia // Marine Geology, 2001, № 172, p. 1-21.Urabe A., Tateishi M., Ionuchi Y. et al.17. Lake-level changes during the past 100,000 years at Lake Baikal, southern Siberia // Quaternary research, 2004, v. 62, p. 214-222.

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METASTABiLiTY iN GAS HYDRATE SYSTEMS

Istomin Vladimir A.1, Kvon Valerii G.1, Chuvilin Evgenii M.2, Nesterov Alexander N.3

1 Gazprom VNIIGAZ JSC, Moscow region, Russia2 MSU, Moscow, Russia3 IKZ, Tyumen, Russia

The metastability problems of gas hydrate systems are discussed.Metastability during gas hydrate formation processes.The following questions are under consideration:

Gas hydrate’s formation from metastable water phases (supercooled water, cubic ice etc.). 1. Determination of equilibrium line for three phase equilibrium “supercooled water — gas hy-drate — gas” (in absence of ice in the system) from experimental data and comparison with thermodynamic calculations.Gas hydrate formation from supersaturated gas water solution. “Memory effect” for second-2. ary hydrate formation and its possible thermodynamic explanation.Metastable hydrate phase formation in the stability zone of another type of hydrate (for in-3. stance, the formation of gas hydrate structure I when thermodynamically more stable the structure II). Formation the mixture of several hydrate structures.The formation of another hydrate phase from previously prepared hydrate.4. Conditions when the formation of hydrate phase with practically empty of small cavities is 5. possible.

Metastability during gas hydrate decomposition processes.Self-preservation and forced-preservation of gas hydrates during surface decomposition pro-1. cess. Thermodynamic conditions for hydrate decomposition to supercoolled water and gas.Some particularities of self preservation effect in porous media.2. Prolonged induction time for hydrate decomposition to ice and gas: metastability without 3. any ice film covering!Spinodal mechanism of gas hydrates decomposition. Is it really possible?4. The classification of metastability of gas-hydrate systems is presented including a thermo-5. dynamic state of gas hydrate phase itself (inner equilibrium or its absence, boundary of a thermodynamic stability, etc.); by quantity of phases in the system (two or three-phase equi-libria with a metastable gas-hydrate phase); by formation of gas-hydrate phase from different metastable aqueous phases.

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GAS SEEpAGE AND pOSSiBiLiTiES FOR THE SHALLOw GAS HYDRATE AccUMULATiON AT THE BARENTS AND KARA SEAS

Korshunov D.A.1, Matveeva T.V.1, Logvina E.A.1, Rekant P.V.1, Shkarubo S.I.2

1 All-Russia Research Institute for Geology and Mineral Resources of the Ocean (VNIIOkeangeologia), St.Petersburg, Russia, e-mail: [email protected] 2 Murmansk Arctic Geological Expedition (MAGE)

Gas emission indications and shallow sediment gas hydrate occurrences in the Arctic seas are still poorly understood due mainly to the lack of direct observation. It is known, that hydrocarbons seepage toward the seafloor ordinary controls formation of the shallow-seated gas hydrate accumulations. Therefore, the aim of this study was to allocate possible shallow-seated gas hydrate accumulations within Barents and Kara seas basing on (1) investigation of high-resolution seismic data from Murmansk Arctic Geological Expedition (MAGE) and VNIIOkeangeologia expeditions; (2) forecast mapping of potential gas hydrate-bearing water areas.

Interpretation of the high resolution seismic images allowed revealing various gas-related acoustic signa-tures in the uppermost sediment. The following types of the acoustic anomalies related with free gas presence in sediment pore space were identified based on the changes of seismic signal amplitude values and acoustic impedance in the wave pattern: (a) acoustic turbidity, (b) columnar acoustic turbidity or gas chimneys, and (c) enhanced reflections with acoustic shadow beneath (Fig. 1).

Totally 58 acoustic anomalies were recognized and mapped over the study area. It is remarkable that seismic images from northern Barents Sea area characterize exclusively by presence of chimney-like anoma-lies (21 gas chimneys from total 58 were detected), whereas images from northern Kara Sea area characterize by presence of all the identified types of the gas-induced anomalies. Specific feature of northern Kara Sea is occurrence of wide-spread acoustic turbidity (more than 25 km wide) and enhanced reflection zones with lengths varying from 2 to 10 km.

In order to define PT conditions of the shallow hydrate formation the CSMHYD Hydrate Program software (Sloan, 1990) was used. The calculations were based on the distribution of measured bottom water temperatures ranging from 0.5 to -1.0°C and from 0.0 to -1.5°C for the Barents and Kara seas, respectively, and assuming the pure methane as a hydrate-forming gas and water salinity of 35‰. As a result, the pres-sure values (water depth function) required for the shallow gas hydrate formation were obtained allowing to predict hydrate-prone areas. These areas with the appropriate PT conditions are limited by minimum water depths of 320 m at the Barents Sea and 280 m at the Kara Sea.

When considering locations of the identified seismic anomalies with respect to those favorable for the shallow gas hydrate formations, it is appeared that 10 from 58 seismic anomalies are occurred within the hydrate-prone areas. For the instance, South Barents Depression, Eastern Novaya Zemlya Trough, and southern part of St. Anna Trough are characterized by combination of gas seepage occurrences and thermo-baric conditions favorable for the shallow sediment gas hydrate formation suggesting these areas as the most perspective for the shallow gas hydrate formation.

This work is supported by OSL-Fellowship program 2010, grant OSL-10-18.

Fig. 1. Examples of gas-induced anomalies recognized on the seismic records: a) acoustic turbidity, b) gas chim-ney, c) enhanced reflection with acoustic shadow beneath.

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pOcKMARK-LiKE STRUcTURES iN THE cHUKcHi SEA

Logvina E.A.1, Matveeva T.V.1, Petrova V.I.1, Korshunov D.A.1, Gladysh V.A.1, K. Crane2, T. Whitledge3

1 I.S. Gramberg All-Russia Research Institute for Geology and Mineral Resources of the Ocean, “I.S. Gramberg VNIIOkeangeologia”, St. Petersburg, Russia, e-mail: [email protected] National Oceanic and Atmospheric Administration, Silver Spring, MD, USA3 University of Alaska Fairbanks, Fairbanks, USA

In the framework of RUSALCA (RUSsian-American Long term Census of the Arctic) Project in Au-gust-September 2009 pockmark-like structures at the water depths of 565-680 m were investigated with a variety of methods, including side scan sonar and subbottom profiler surveys, sedimentological and geo-chemical analyses of cores and sediment pore waters studies. These structures were discovered by USCGC during 2003 HEALY-0302 cruise in a shallow region of the Chukchi Cap at approximately 76° 30’N and 163° 50’W (Mayer et al., 2009). It is necessary to mark that the coring of the pockmark field was carried out for the first time in 2009.

More than 20 circular depressions were revealed on the side-scan sonar images. These depressions are cone-shaped, as deep as 40-50 m and 150- 850 m in diameter and in a good accordance with USGS multi-beam data (Mayer et al., 2009). Based on results of the seismic survey, three pockmarks were choosing for the coring. Sediments recovered from these pockmarks represented by alternation of banded greenish and brownish clayey silts testifying to periods of glacial and interglacial sedimentation, respectively that is char-acteristic for the ‘normal’ Arctic marine sedimentation. It should be noted, that contrary of our expectations no evidences of gas presence in the recovered sediments were observed. The feature that defines these sedi-ments from those, accumulated at normal marine environment, is the presence of brecciated sediment struc-tures (different in color). These breccia-like sediments resembling mud volcanic breccias was represented by silty-clay matrix brownish-gray in color with dark-gray dense clay inclusions with sizes up to 1.5 cm and rocks clasts (up to 4cm). The sediment characterizes by high content of carbonate (allothigenic dolomite) reaching in some core intervals up to 55%.

Pore water chemistry has shown that the major ion concentrations in the pore waters are higher than those of the bottom water from most of the other RUSALCA coring stations. In addition, analyses revealed considerable fluctuations with depth in the concentrations of potassium, sodium, and magnesium content at all the sampled structures. These fluctuations may indicate upward water infiltration. In addition, Oxygen isotope composition in the pore waters gets heavier with increasing Cl- concentration suggesting possible upward infiltration of water with chemical and isotopic composition different from the seawater above. Thus, some of the studied pockmarks characterize by indications of the upward water infiltration most probably occurring in the past.

On the other hand, according to our study of dispersed organic matter (DOM) in the sediments, sterane indexes of the maturity (20S/20S+20R C29) are evidence for a post-diagenetic stage of the DOM transfor-mation. The specific character of composition and distribution of triterpanes, steranes, and arenes signifies a mixed origin and a considerable post-diagenetic level of the organic matter maturity. Aromatic hydrocarbons represented mostly by phenanthrene and its alky-homologies with anomalously high content (> 3000 ng/g) were associated with a high value of MPI1 index (up to 0.75) suggest a high degree of the OM maturity. The highly matured OM may have been supplied to the studied sediments by (1) ice rafting, (2) suspended or-ganic material transported by river run-off or (3) mud flows from deeply buried sediments (result of a mud volcano activity).

It is obvious that pockmarks are not active now and besides have undergone a number of stages of activization-attenuation. Since the origin of the pockmark structures is thought to be related to the faults occurring below and visible on the deep seismic section obtained by USGS, the faults may serve as fluid infiltrations pathways.

REFERENcES:Mayer A. Larry, Armstrong A. Andrew and Gardner V. (2009) James Mapping in the Arctic Ocean in Support of a Potential Extended Continental Shelf.

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GAS HYDRATES OF THE RUSSiAN ARcTic SEAS: DiSTRiBUTiON AND RESOURcE pOTENTiAL

Matveeva T., Krylov A.

All-Russia Research Institute for Geology and Mineral Resources of the Ocean, (VNIIOkeangeologia), St.Petersburg, Russia, e-mail: [email protected]

Since natural gas hydrates are a vast potential, though not presently commercial, source of unconven-tional gas and possible factor of geohazards, there is necessity to attract considerable attention to the subma-rine gas hydrate research at the Arctic shelf and deep water areas. At present, Arctic gas hydrates is still the subject of theoretical investigations. Our long-term activity in the gas hydrate studies have shown that due permafrost presence gas hydrate accumulations (GHA) of the Arctic can be subdivided into two main groups according their origin.

1. Cryogenetic GHAs forming due to exogenous cooling of the sediments during formation of perma-frost:

- subaqueous GHA within the relic permafrost;- gas hydrates in frozen rocks forming from a gas previously dissolved in waters of the frozen sediments

due to self-preservation.2. Filtrogenous GHA precipitating from water and gas infiltrating toward the seafloor:- shallow-seated GHA related to concentrated gas infiltration;- deep-seated GHA that are controlled by dissipated gas infiltration.Eastern-Arctic shelf and the Kara Sea characterize by predominance of the second type of gas hydrate

occurrences, whereas the Western-Arctic shelf - by the first type.In this study gas hydrate environments and potential hydrate-bearing water areas of the Arctic Ocean

and Russian Arctic seas were considered and estimated based on the analysis of PT conditions at the seafloor and within sediments. As a result both water areas characterizing by presence of favorable PT conditions for the gas hydrate formation and those where such conditions are absent were allocated. The following criteria were the base for the recognition of the hydrate-bearing water areas: on the Arctic shelf (with the exception of deep oceanic trenches) their bounded by relic permafrost distribution (continuous and insular). These areas characterize by the permafrost base (~0°C isotherm) occurring at the depth exceeding 260 m from sea surface (independently from the water depth). For the rest area 3°С/ 100 m value of thermal gradient was applied.

The permafrost-free water areas with water depth of 250 m and less and the areas where gas generation conditions are not sufficient to produce and preserve enough amount of gas are hydrate-free. Since the main mapping criterion was a thickness of sediments, hydrate-free areas are those where thickness of sediments does not exceed 0.5 km.

Distribution of bottom temperatures and submarine permafrost allow to estimate gas hydrate PT stabil-ity conditions and to allocate the GHSZ along the area and across the section. As a whole, the mapping pro-cedure and GHSZ recognition resolves into coinciding of measured temperature values (and/or geothermal gradient values) and pressure value in the certain location with one or another gas hydrate stability curve.

When considering the factors controlling thermobaric stability conditions of the Arctic gas hydrates it is appeared that GHSZ can be detached and non-detached from the seabed. The detached GHSZ occurs within depth interval varying from meters to 200 m below the seafloor. Non-detached GHSZ is typical for the continental slope and for the relatively deep-water permafrost-free shelves. The detached GHSZ is con-trolled either by relic permafrost presence (of various thickness) or confines to permafrost-free shelves char-acterizing by bottom temperatures low enough and significant water depth (although not enough to provide pressure required for the gas hydrate formation just on the seafloor).

Gas hydrates could potentially be found within about 37% of the Arctic shelf off Russia. The total vol-ume of the GHSZ for hydrates of all the abovementioned types is estimated as much as 3.18·1015 cubic me-ters with potential gas resources (for the continental slopes and trenches off Russia and the shelf Arctic seas) of more than 10 000 billions cubic meters.

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REGULARiTiES iN THE DiSTRiBUTiON OF GAS HYDRATES iN THE SEA OF OKHOTSK

Obzhirov Anatoly1, Baranov Boris2

1 V.I.Il’ichev Pacific Oceanological Institute FEB RAS, 690041, Baltiyskaya St., 43, Vladivostok, Russia, e-mail: [email protected] P.P. Shirshov Institute of Oceanology, Moscow, Russia

Eleven gas hydrate fields in the subsurface sediment were found at the Sakhalin slope of the Sea of Ok-hotsk during our investigations from 1991 to 2009. All these gas hydrate occurrences are related to methane flux from the sediment to the seawater. For the first time gas hydrates in the Sea of Okhotsk were discovered in the subsurface sediment on the western slope of Paramushir Island in 1986. The first flux of methane bubbles into the water column was found at the slope of Paramushir in 1983 at the area, where gas hydrates were recovered from the subsurface sediments (from the depths of 1-5 m below sea floor) (Zonenshain et. al., 1987; Gaedicke et. al., 1997). The first flux of methane bubbles into the water column on the North-East Sakhalin slope was found in 1988 (Obzhirov et. al., 1989). It is in this area in 1991 gas hydrates were discov-ered in near surface sediment as well (at the depths of 1-5 m below sea floor) (Ginsburg et. al., 1993).

Later during 1998-2004 in the framework of German-Russian KOMEX, Russian-Japanese-Korean CHAOS (2003, 2005-2006), and Russian-Japanese-Korean SAKHALIN (2007-2012) projects comprehen-sive studies aimed on the search of the methane seeps and gas hydrates were performed by POI FEB RAS (Russia), IO RAS, GEOMAR (Germany), and VNIIOkeangeologia (Russia) at the shelf and slope of NE

Sakhalin (Obzhirov, 1993; Obzhirov et.al., 2002; Obzhirov et.al., 2004).

The following regularities were established during our investigations of the gas seepage fields off NE Sakh-alin by using of geological, geophysi-cal, and hydro-acoustics methods.

1. New methane seeps are ap-pearing and detecting year by year. In most seepage locations methane concentrations in the water column vary from 1000 to 10000 nl/l; meth-ane content in sediment varies in the range of 10-100 ml/l. Thus, the con-tents of methane within the studied seepage sites from 100 to 1000 times exceed those of background values. It should be noted, that during summer 2009 the number of methane seeps on the Sakhalin shelf and slope has in-creased up to about 500 (Fig. 1).

Fig. 1 The map shows a region where detailed gas geochemical investiga-tions have been carried out. Many new flares were found on North-East slope of Sakhalin in the Sea of Okhotsk. Red circles indicate flare positions.

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2. The methane fluxes occurrences in most cases confine to fault zones.2.1 Sakhalin shelf is characterizing by the presence of numerous oil and gas fields. The thickness of sedi-

ment within these fields reaches 7-9 km at the shelf and about 5-6 km at the slope. Most probably, methane seeps confines to these deep gas deposits.

2.2 Methane monitoring results showed that intensity of the methane fluxes is increased with the in-creasing of seismotectonic activity of the study area during period from 1988 up to date (Fig. 2). The increase of the seismotectonic activity is expressed in numerous earthquakes in the Neftegorsk (1995), Uglegorsk (2001), Khokkaido (2003), Nevel’sk (2007), and others.

2.3 When methane bubbles pass through the sediment the gas hydrates form in near surface sediment within the gas hydrate stability zone. Free gas accumulates below this zone (bottom gas hydrate thickness, BSR). An activation of the fault zones induces increase of fluid-conductors that is resulted in the free gas (mostly methane) seepage into the seafloor and water. The high temperature and low pressure within the ac-tive fault zones are the reason for the decomposition of gas hydrates occurring in the zone of their stability and, therefore, for the methane release.

2.4 Secondary gas hydrate formation in the subsurface sediment takes place when methane reaches the seafloor under the low temperature conditions and the water depths more than 400 m. The size of these secondary hydrate layers and fragments does not exceed first centimeters. A large sample representing by massive hydrate layer with the thickness of about 40 cm was remarkable.

Fig. 2 Variations in methane concentrations in the water column and the number of flares on the North-East Sakhalin shelf and slope. Triangles show the number of flares, squares depict methane concentrations in bottom water.

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3. The seafloor within the methane flux areas is often destroyed that is resulted in the formation of holes and hillocks resembling mud volcano-like structures. Diameter of one of the structures is estimated to be of about 100-800 m.

4. A new assemblages (numerous shells and other benthos, crabs and fishes) usually occur on the seafloor and carbonate fragments and concretions form in the near surface sediment layers within the methane flux areas.

Thus, the increasing number of the methane flares and methane concentrations in the water column since 1988 are obviously related to the seismotectonic activation of the Sea of Okhotsk. This idea is sup-ported by earthquake events and mud volcano eruptions on the eastern Sakhalin. The seismotectonic oscil-lations lead to the opening of fault zones and, therefore, can induce migration of the gas-containing fluids. The average annual methane flux from the sediment into the water column and further to the atmosphere within the Sakhalin shelf and slope is estimated to be 1000000 m3. Thus, comprehensive investigations in cooperation with international institutions allow us to discover gas hydrates and to understand formation/dissociation regularities of the gas hydrate in the Sea of Okhotsk.

REFERENcESGinsburg G.D., Soloviev V.A., Cranston R.E., Lorenson T.D., Kvenvolden K.A.1. (1993) Gas hydrates from the continental slope, offshore Sakhalin Island, Okhotsk Sea //Geo-Marine Letters, 13, 41-48.Gaedicke Ch., Baranov B. et. al. 2. (1997) Seismic stratigraphy, BSR distribution and venting of methane –rich fluids west off Paramushir and Onecotan Island, Northern Kurils // Marine Geology, V.116.3.Obzhirov A.I., Kazansky B.A., and Melnichenko Yu.I.3. (1989): Effect of the sound scattering in water of the Okhotsk Sea. // Pacific Geology, N2: 119-121 (in Russian).Obzhirov A.I. 4. (1993): Gas geochemical fields in bottom water of seas and oceans; Science Publ., Moscow: 139 pp. (in Russian).Obzhirov A.I. et .al.5. , (2002) Methane monitoring in the Sea of Okhotsk. Dalnauka, Vladivostok, 250 p. (in Russian).Obzhirov A., Shakirov R., Salyuk A., Suess E., Biebow N., Salomatin A. 6. (2004). Relations between meth-ane venting, geological structure and seismo-tectonics in the Okhotsk Sea//Geo-Marine Letter. Vol. 24, № 3., p. 135–139.Zonenshain L.P., Murdmaa I.O., Baranov B.V., et.al,7. 1987, Submarine gas vent in the Sea of Okhotsk to the west from Paramushir Island: Oceanology, 27, 795-800 (in Russian).

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THE UNcONvENTiONAL GAS SOURcES AND pROSpEcTS OF THEiR DEvELOpMENT

Perlova E.V., Leonov S.A.

Gazprom VNIIGAZ, Moscow region, Russia, e-mail: [email protected]

At present there is no definition of the unconventional natural gas sources. Based on the geological, technological, and economical criteria by International Gas Union (IGU) it is possible to estimate com-mercial value of the unconventional gas sources (natural gas hydrates, coalbed methane, and shale gas). The efficiency of a deposit development is determined by a balance of its geological (permeability, free gas con-tent, depth of occurrence), technological (density of resources, gas flow rate, wellhead pressure), economi-cal (supply distance, natural gas price), and environmental parameters. The study of the unconventional sources is important by the following reasons. First, the unconventional gas sources are widespread. Their resources are huge and locations are close to the gas consumption regions. This is the reason why their eco-nomical potential is coming near to that of the conventional gas. Second, the study of unconventional gas sources is necessary because their growing importance due to the changes in global gas market. For example, more than 50% of gas production in USA comes from unconventional domestic gas sources. So, based on the experience of USA many Russian gas consumers propose development of their own unconventional gas sources in order to decrease gas import.

Natural methane hydrates possess the best market opportunities in comparison with other unconven-tional gas sources due to their wide spread, shallow depths occurrence (in comparison with con-ventional gas) and huge resource potential ranging from 2500 to 21000 TCM. The temperature factor impacts principally on the formation of gas hydrate zone in continental environment. The gas hydrate accumulations are always associated with the permafrost areas. The pressure factor has the key impact on the occurrence of hydrates under the seabed. The hydrate-bearing onshore and offshore areas appear to be a proved matter. The works targeted on the hydrate exploration are not widely carried out: there are very few examples of special geological studies and testing drillings for natural gas hydrates. This is stipulated by low exploration maturity of gas hydrates. The formation mechanism of gas hydrate accumulations is not still fully understood. The direct technologies of the exploration and mapping of hydrate-bearing deposits are poorly developed (especially, onshore). These investigations are of high costs and require the unique equipment and high expenses for the specialists training. Works at the onshore Mallik field (the delta of Mackenzie River, North-West Canada) and investigations in the Nankai Trough (offshore Japan) for submarine gas hydrates are the most representative.

Russia, as a northern country has substantial potential for the gas hydrates exploration. The special stud-ies aimed on the industrial production of natural gas from hydrate accumulations have not been initiated in Russia yet. Nevertheless, there are high prospects of gas hydrate accumulations over the Russian territory. The geological data allow to forecast hydrate gas resources and to map out the top-priority sites for pilot test-ing and geological prospecting works.

The prospects for commercial hydrates development in Russia are the followings:1. The costs of gas production from hydrates are incompatible with those from conventional

gas sources. Apparently, the gas hydrate deposits will not be commercially developed during next 15-20 years.

2. It is reasonable to believe that technological progress in gas production will change the state of affairs and ensure the economic viability of the hydrates development.

3. The continental hydrate accumulations are prospective for development since the established pro-duction and transportation infrastructures are already existed over the areas of hydrates occurrence.

4. The Yamburg oil- and gas condensate field (West Siberian OGP) and the western part of the Sea of Okhotsk (Deruygin Basin) are the high-priority targets for the geological prospecting and pilot testing drill-ing on natural gas hydrates.

The most part (90%) of methane in coalbed methane deposits is in a stranded (hard to recover) form absorbed in coal. The well-known San Juan coal deposit (75% coalbed gas production in USA) is not a pure coalbed methane deposit. It is associated with the local accumulation of conventional gas in coalbed forma-

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tions. The commercial production of coalbed methane is a complex engineering and economic problem caused by retained form of gas occurrence. Moreover, methane is considered as a dangerous for coal mines operating. It should be eliminated away before starting a coal deposit development. On the other hand, the coalbed methane is considered as an important part of fuel and energy sector for the coal-producing coun-tries. The world experience shows necessity in development of possibility and economic effectivity of large-scale coalbed methane development. Its production is reached up to 52 Bcm in USA, 2.4 Bcm - in Canada, 0.7 Bcm - in Australia, 1.1 Bcm - in China (2005). The recourse potential ranges from 200 to 250 TCM. The coalbed methane production in USA, which is leading in this sector, reaches 50 BCM (more than 9% of total gas production). In many coal-producing countries (Italy, Germany, South Africa, India, Venezuela, Argentine, etc.) there are National programs for methane coalbed exploration.

The industrial development of coalbed methane deposits is putting on during last decade in Kuznetsk methane-coal basin (Russia). JSC “Gazprom” started this project in 2003. “Promgas” Ltd. (associated with JSC “Gazprom”) is the project operating company. Thus, JSC “Gazprom” enlarges its own hydrocarbons resource base in order to provide a wide-scale gasification of the southern regions of Western Siberia and to increase export to the Asian-Pacific region. The works on the coalbed methane production are carried on gradually to reduce geological and engineering risks that are specific for the projects on the early stages of their implementation.

The Russian prospects for coalbed methane development are:1. The first-priority object for test production is Taldinskaja area in Kuznetsk coal basin. Pechora, Tun-

gus, Lena, and East Donets Basins are perspective for the development on the basis of geological and litho-logical criteria.

2. It is unlikely that the commercial production of the coalbed methane starts before 2030 because of the economical reasons.

3. The production of coalbed methane for local gas needs is perspective at present.4. It is important to organize the prospect evaluation surveys on coalbed methane at perspective Rus-

sian basins.Up to date, shale gas is one of the most perspective types of unconventional gas resources. Its production

is constantly growing in United States (up to 300% from 1996 to 2006). The European countries are con-sidering shale gas as an alternative to the conventional gas supplying from Russia. An achievement of some projects like “Mako” (Hungary) will allow partially substitute the imported gas with local shale gas.

At present the shale gas is considerable expensive than traditional one. Nevertheless, it development can strongly influence the global gas market. The shale gas resources range from 380 to 420 TCM. For the day, more than 40000 wells produce methane from 5 largest American shale basins. A number of countries carry out prospecting works at new shale gas fields and preparation of the existing fields for development. Nevertheless, the wide-scale shale gas production in Europe is not realistic in the near future because of the technological and ecological problems. The drilling of dozens of thousands wells in densely populated area is unlikely. This can essentially decrease the scale and economic feasibility of the shale gas exploration in Europe.

The Russian problems for shale gas development are the followings:1. Low level of the geological and geophysical extent of exploration that can result the low efficiency of

exploration. The exploration extent of shale basins in USA are notably higher, which allows making realistic geological and technological models.

2. The lack of the production technologies. The horizontal drilling and hydraulic fracturing are aimed to other technological objects. Their application for the shale gas recovery depends from the geological and ecological features.

3. Low scale of drilling. It is necessary to drill thousands of wells per year in order to provide shale gas economical feasibility in Russia.

4. The lack of economic and law incentives in Russian legislation (like American section “29 tax cred-it”).

These are common problems for all types of the unconventional gas development in Russia.

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THE wEST– SiBERiA HYDRATES-BEARiNG pROSpEcTS

Perlova E.V., Leonov S.A.

Gazprom VNIIGAZ, Moscow region, Russia, e-maei: [email protected]

The search, prospecting, and development of natural hydrate accumulations are perspective for the resource potential increase. The upper parts of the sedimentary cross-section of the giant West-Siberian gas fields are most promising for the prospecting and development of the hydrates. The hydrate accumula-tions are associated with conventional gas deposits that may promote the hydrate prospecting and potential utilization. Formation of large hydrate accumulations in continental environment is controlled by a number of factors. These factors can be divided into two categories. First category of the factors includes climatic (paleoclimate) and thermobaric conditions (temperature and pore pressure under the hydrate formation) and paleoclimatic conditions favorable for the hydrates preservation in sediments. Another category of fac-tors consists of geological and tectonic features of the region including the presence of collectors overlying by seals, and fracture zones. All of these factors determine the sources of hydrate-forming gas and potential sites for gas hydrate accumulations.

These two groups of factors are not completely studied in northern part of West Siberia. The special works targeted on the natural gas hydrate investigations similar with those conducted at Alaska and Canadian North were not carried out there. The results of our works are based on determination of most important factors controlling formation of large (industrial-scale) hydrate accumulations in permafrost.

The influence of climate (paleoclimate) and thermobaric factors on the hydrate formation was con-firmed by experimental studies in Alaska. Since West-Siberia is the permafrost region, its territory can be ranged by topology and thickness of gas hydrate stability zone (GHSZ) on the basis of permafrost thick-ness and temperature regimes evaluations. The severe climate during Pleistocene stipulated the progres-sive permafrost growth there. The temperature oscillations in that period were constantly below zero. The thaw of permafrost rocks occurred at the surface part only at the South of the region. Similarly, according to paleoclimate reconstruction, an optimum both of rocks long-term freezing and of cryolithozone pres-ervation was established during Pleistocene for the gas hydrate accumulations at Alaska and Canadian North.

At the northern part of West Siberia temperature conditions of permafrost rocks, which are defined by complex of zonal, regional, and local factors, determines an existence of gas hydrate stability zone. At the same time, baric conditions are also affected the formation and preservation of gas hydrate accumulations. Thus, existing gas accumulations may be transformed to hydrate state due to external change of the baric conditions.

As regards to geological and tectonic features of the northern part of West Siberia, its prospects of the hydrate formation are defined by existence of regional reservoirs within the limits of GHSZ and regional cap rocks.

One more factor controlling the formation of concentrated gas hydrate accumulations is an existence of fluid migration pathways from underlying gas-bearing horizons, especially paleo-faults in the Earth crust. The existence of neo-tectonic faults, dislocations, and fractures in the underlying cap rocks can be served as an additional opportunity for vertical and lateral hydrocarbon migration.

Additional factor, determining the formation of large commercial gas hydrate accumulations is an ex-istence of present-day gas inflow renewing these accumulations. The existence of such inflows suggests in-tensive deep generation of hydrocarbons and in case of high-quality reservoirs and cap rocks presence it can lead to formation of underlying traditional hydrocarbon deposits.

Next factor determining the formation of gas hydrate accumulations is an existence of sufficient vol-umes of water and hydrate-forming gas. Gas in sedimentary section can be formed in situ as the result of bacterial transformation of organic matter (biogenic) or deep migrated upward from underlying horizons (thermogenic). The comparison of isotopic-geochemical data from northern West Siberia, Alaska, and Ca-nadian North shows the similar change in the isotopic composition of methane suggesting favorable forecast of hydrates formation within Russian areas.

Based on the thermobaric and structural factors we have zoned the area of research on the hydrate-bearing perspective zones (upper-Cenomanian sediments). It has been established that:

- the thickness of methane hydrate stability zone varies from 300 to 600 m;

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- Nadym-Pur-Taz region is the most perspective hydrate-bearing region taking into account the localiza-tion and thickness of GHSZ and anomalously low thermal gradient in permafrost;

- in Nadym-Pur-Taz region two regional stratigrafic complexes (lower-Paleogene continental sub-suite of Tibey-Salin suite and Maastricht-Dutch horizons of Upper Cretaceous Tanam suite) are entirely or partly occur in the methane hydrate stability zone.

Based on the complex of factors controlling hydrate-bearing perspectives (square of studied territory and the proximity to infra-structure), the northern part of Nadym-Pur-Taz region can be suggested as the most perspective area (especially its Upper-Cenomanian gas fields). We also suggest Yamburg and Zapolyarnoe fields (Kharvutinskaya and Aneryakhskaya areas, first of all) as the first-priority objects for the experimental and methodic works on gas hydrates. The first-priority sites for these studies are gas fields including stations 4 and 9 (Yamburg field) and 1 and 3 (Zapolyarnoe field).

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RELATiONSHip BETwEEN GASHYDRATE FiELDS AND METHANE FLUx iN THE SEA OF OKHOTSK

Pestrikova Natalia, Obzhirov Anatoliy

V.I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Baltiys-kaya Str. 43, Vladivostok, 690041, Russia, e-mail: [email protected]

Gasgeochemical investigations in the Sea of Okhotsk were carried out during 1984-2009 by gasgeo-chemistry laboratory POI FEB RAS. The anomalous methane fields (with respect to background methane concentrations) are established in the seawater at eastern Sakhalin shelf and slope. Sharp increase of meth-ane concentration in the water column was detected on the boundary of 1988-89 years at this area: two-three times for the background values (70-80 nl/l) and more than 100 times for anomalies (up to 10 000–20 000 nl/l).

The data analysis allows to conclude that this phenomenon is conditioned by an increase of seismo-tectonic activity. Fluxes of natural gas from the source-rock to the seabed, from seabed to the water and, finally, to the atmosphere get more intensive due to renew of fault zones. As a result, the number of methane vents on NE Sakhalin slope was increased from 2-3 to 400 at present. The most representative hydroacoustic anomalies (“flares”) mapped there and related to methane hydrates were studied by direct methods.

Two gas hydrate-bearing areas are known in the Sea of Okhotsk: slope of NE Sakhalin (the western part of the Deryugin Basin) and slope off NW Paramushir Island (SE part of Golyginskii flexure) [12, 4, 1, 2, 10, 5, 3, 7, 8]. These geological structures are characterized by sufficient potential of hydrocarbons generation [11]. Gas hydrates associated with these gas vents are located near the deep faults.

The most noticeable anomalous methane fields in the water column with methane concentrations 100 times exceeding background values are formed on the shelf and slope of NE Sakhalin. These anomalies in methane concentrations are referred to submarine gas discharge zones. For example, Obzhirov, Gizella, and Ervin characterize by methane concentrations in the bottom waters up to 23 000 nl/l (2000), Hieroglyph and Chaos – 2000 nl/l, Obzhirov – 260 000 nl/l (August, October, 2003) etc. The process of methane discharge (as a result of gas hydrate decomposition) was for the first time found in 1986 on the north-western slope of Paramushir Island [6]. In this area gas bubbles (mainly methane) at the water depth of about 800 m rose up to 200-300 m from the seafloor to the water column and created a sound-scattering acoustic anomalies (“flares”) at the echograms. As a result of investigations carried out by Institute of Volcanology and Oceanol-ogy [12], gas hydrates were found in the sediments of the methane seepage area.

The study of gasgeochemical fields in the Sea of Okhotsk has shown that on the boundary of 1988-1989 there was a sharp increase of methane concentration in bottom seawater [6]. The sharp increase of methane concentration in the water of the Sea of Okhotsk is probably connected to seismotectonic activa-tion of the Sea of Okhotsk area. As a result, a thermal flow through fault zones has amplified and the rocks containing gas hydrates and free gas beneath were broken. Natural gas escaping both from decomposed gas hydrates and from deep gas reservoirs beneath the hydrates began to act to the seafloor that inducing methane bubbling from the seafloor to the water and in some place from sea surface to the atmosphere. Methane fluxes resulting from the gas hydrate decomposition created sound-scattering anomalies (flares of various forms) on echograms. At first, two hydroacoustic anomalies describing methane fluxes were recorded. By 1995 their amount is increased to about 30. In 1995 there was an earthquake on the north-east Sakhalin at Neftegorsk area. By 2002 the number of methane vents in the Sea of Okhotsk is exceeded 100.

The results of research suggests that all these natural gas vents are referred to the zones of faults inter-section (of north-western and north-eastern directions) controlled by the East Sakhalin Fault Zone. Obvi-ously, the Zone is responsible for the seismotectonic activation of north-eastern shelf and slope of the Sea of Okhotsk [9]. It was established that continuation of the seismotectonic activation of the Sea of Okhotsk region in 2002 is resulted in the speeding-up of the gas hydrate decomposition and, therefore, in an increase of the methane vents number. The data obtained during 2003-2005 indicate further intensification of the seismotectonic activation and confirm aforesaid. The methane monitoring carried out within the area of gas vents has shown that the methane concentrations measured from May to June, 2005 remained as high as it was determined during 2003 expedition. Since 2003, 400 methane fluxes were revealed in the north-western part of the Sea of Okhotsk during further investigations (fig. 1).

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Analysis of the data obtained during 1998-2006 has shown that there are no regularities responsible for the quantitative changes of gas hydrate distribution with depth. However, it should be noted, that at the central parts of the gas vents gas hydrates occur at the shallower sediment depths than that at the periphery of the vents. We suppose that this is due to the secondary gas hydrate formation within the zones of gas hydrate destroying located near the active deep faults, which are conductors and generators of the methane fluxes.

Methane concentrations in the gas hydrate-free cores as a rule increase from the depth of 200 cm below seafloor (0.1 — 1 ml/l and higher). This is probably can be explained by the presence of sulfate-reduction zone. In the sediments containing gas hydrate this regularity is not observed because gas hydrate-bearing sediments locating at different subbottom depths contain a huge volume of methane. In the gas hydrate-bearing cores (independently from the depth) methane concentrations are increased to 500 ml/l and reach-ing sometimes of 3000 ml/l.

The obtained data indicate the urgent necessity of study of gas hydrate formation-dissociation mecha-nisms and the influence of the methane flux from hydrocarbon sources on the environment.

REFERENcESBiebow N. and Huetten E. (eds.) 1. KOMEX Cruise Reports I & II RV Professor Gagarinsky, Cruise 22, RV Akade-mik M.A. Lavrentyev, cruise 28. GEOMAR Report 82 INESSA. Kiel, Germany. 1999. 188 p.Biebow N., Kulinich R., and Baranov B. (eds.). Kurile Okhotsk Sea Marine Experiment (KOMEX II). Cruise 2. Report: RV Akademik Lavrentyev, cruise 29. Leg 1-2. 2002. 190 p.Dullo W.-Chr., Biebow N., and Georgeleit K. (eds.). 3. SO178-KOMEX Cruise Report: RV SONNE. Mass exchange processes and balances in the Okhotsk Sea. Germany. 2004. 125 p.Ginsburg G.D., Soloviev V.A.4. Submarine gas hydrates. Saint-Petersburg: VNIIOkeangeologia, 1994. 199 p.Matveeva T., Soloviev V., Shoji H., Obzhirov A. (eds.)5. . Cruise Report CHAOS-I: RV Akademik M.A. Lavrentyev, cruises 31 and 32. SPb.: VNIIOkeangeologia, 2005. 164 p.Obzhirov A.I., Astahova N.V., Lipkina M.I., Vereshchagina O.F., Mishukova G.I., Sorochinskaya A.V., Yugai I.G. 6. Gasgeochemical zoning and mineral associations of the bottom of the Sea of Okhotsk. Vladivostok: Dal’nauka, 1999. P. 184.Obzhirov A.I. (eds.)7. Complex geological, hydrological, gasgeochemical and geophysical research in the area of

Fig. 1 Hydroacoustic anomalies (from Salomatin, 2008).

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gashydrate accumulation in the Sea of Okhotsk: CHAOS-2 Cruise Reports, RV Akademik M.A. Lavrentyev, cruise 36. Vladivostok. 2005. 123 p.Obzhirov A.I. (eds.)8. Complex litological, hydrological, gasgeochemical and geophysical research in the area of gashydrate accumulation in the Sea of Okhotsk: CHAOS-3 Cruise Reports, RV Akademik M.A. Lavrentyev, cruise 39. Vladivostok. 2006. 62 p.Obzhirov A.I., Salyuk A.N., Shakirov R.B., Druzhinin V.V., Mishukova G.I., Ageev А.А., Salomatin A.S., Pestriko-9. va N.L., Veselov O.V., Kudel’kin V.V. Methane flux and gashydrates in the Sea of Okhotsk // Science and technics in the gas industry. Moscow: Publishing house OOO “IRTS Gasprom”, 2004. № 1-2. P. 20-25.Obzhirov A.I., Shakirov R.B., Mishukova G.I., Druzhinin V.V., Luchsheva L.N., Ageev A.A., Pestrikova N.L., Obzhi-10. rova N.P. Study of the gasgeochemical fields in the water environment of the Sea of Okhotsk // Vestnik FEB RAS. Vladivostok: Dal’nauka. 2003. № 2. P. 118-125.Veselov O.V., Iien A.Ya., Kononov V., Kochergin E.V., Patrikeev V.N., Semakin V.P., Senachin V.N., Ageev B.N., 11. Vasyuk I.B., Volgin P.F., Gretskaya E.V., Zlobina L.M., Giguliev V.V., Kornev O.S., Kochergin A.V., Kudel’kin V.V. Tectonics and hydrocarbon potential of the Sea of Okhotsk. Vladivostok: FEB RAS, 2004. 160 p.Zonenshain L.P., Murdmaa I.O., Baranov B.V., Kuznetsov A. P. and others. 12. Submarine gas vent in the Sea of Ok-hotsk to the west from Paramushir Island // Oceanology. 1987. V. 27. Publication 5. P. 795-800.

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pEcULiARiTiES OF BiOGEOcHEMicAL cHARAcTERiSTicS THE GAS HYDRATE-BEARiNG SEDiMENTS OF THE AREA OF THE GOLOUSTNOYE

(LAKE BAiKAL, RUSSiA)

Pogodaeva T.V., Zemskaya T.I., Pavlova O.N., Suslova M.Yu., Khlystov O.M.

Limnological Institute SB RAS, 3, Ulan-Batorskaya, Irkutsk 664033, Russia, e-mail: [email protected]

Lake Baikal is the only known fresh-water gas hydrate-bearing basin. Four mud volcano provinces (near Posolsky Bank, near Olk’hon Gate, near Kukuyu Canyon, and opposite to the Peschanaya Bay) uniting 14 mud volcanoes, deep-water oil and Gorevoy Utes gas seep field and Goloustnoye gas seep field were discovered here during recent years. Subsurface gas hydrates forming different textures of hydrate-bearing sediment occur in the seven mud volcanoes (of three provinces) and within both seep fields [1].

The purpose of this presentation is to reveal the origin of the water involving in the subsurface gas hydrate accumulations from area of the Goloustnoye seep.

Chemical and microbiological investigations of the near-surface gas hydrates aimed on recognition of a fluid short run activity were done within the Goloustnoye seep during 2008 year (in different months). Investigations were carried out in winter from the ice of the lake (two expeditions) and in summer time (three expeditions). Changes in pore waters chemical composition and distribution of microorganisms utilizing of hydrocarbons (with different chain length) in anaerobic and aerobic conditions mark trends of events in the sediments.

Pore waters sampled in March are characterized by low concentration of dissolved salts and bicarbonate and calcium ions (Fig.1). The HCO

3- concentrations along all the studied cores did not exceed 1.6 mM. Composi-

tion of the pore waters in different sediment horizons was virtually identical with the exception of some horizons where pore water with anomalous low sum of ions was found (that is resulted from the gas hydrates presence).

Fig. 1 Profiles of bicarbonate and sulfate ions distribution in pore waters from sediments of Goloustnoye seep.

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An absence of sulphate-ion in pore waters from this site was determined even in sub-surface (0-10 cm) sediment layers in contrast to other sites including background ones. During microbiological studies, dominance of anaero-bic hydrocarbon-oxidizing microorganisms (HCOM) was observed. Their number was twice higher than that of aerobic HCOM. It should be noted, that the latter was found in surface sediment layers (0-10 cm) only. Microor-ganism distributions in cores from this area have been investigated weekly and they are appeared to be identical. Consistency of chemical profiles, the absence of sulphate-ion in the pore water from near-bottom sediments, and low value of hydrocarbonate-ion in deeper sediment layers suggest an inflow of water from below.

Pore waters sampled in June were characterized by presence of sulphate-ion in near-bottom sediment layers. Near-bottom water saturating the subsurface sediments during pauses in the upward water discharge may serve as a source of this pore water. Pore waters from deeper sediments layers are characterized by low hydrocarbonate-calcium mineralization similar with that observed in March. Other pattern was revealed for the microbial distri-bution. Cultured anaerobic HCOM were not recorded. Aerobic HCOM were found in deeper sediment layers (35-100 cm).

Aerobic HCOM distribution studied during July and August appeared to be the same as it was observed in March. Similar pattern was obtained during investigation of distribution of organotrophic spores form bacteria and bacteria of genus Pseudomonas in the same cores. An absence of sulphate-ion was documented in composition of pore water both in August and in March. Bicarbonate–ion and calcium-ion patterns reflect decreasing trends in concentrations of these ions with sediment depth (measured concentrations are lower than those observed in March). The obtained results allow to suggest discharge of water with anomalous low concentration of dissolved salts within this area.

Therefore, both discharges of gases and water with low concentration of dissolved salts are identified and studied within Goloustnoye cold seep area. Fluctuation in the aerobic and anaerobic microorganisms growth is established in the studied fluid discharge area. Most likely it is caused by different intensity of gas-contained fluid input that is resulted in changes of chemical pattern and, therefore, induced the growth of different HCOM groups.

This work was supported by the programme of Russian Foundation for Basic Research No 08-05-00709 and 10-05-00681, Integration Project SB RAS No. 27, and Presidium Programme RAS, Project 20.9

REFERENcESKhlystov O.M., Zemskaya T.I., Grachev M.А. (2007). Gas Hydrates of Lake Baikal: History and Outlook of their Study. Collected papers of First International Scientific Conference «World Gas Resources and Leading-edge Tech-nologies of their Exploration (WGRR-2007):163-174.

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GAS-GEOcHEMiSTRY FEATURES OF SEDiMENTS OF THE EAST-SiBERiAN SEA (RESULTS FROM 45 cRUiSE Rv

«AKADEMiK M.A. LAvRENTYEv», 2008)

R.B. Shakirov1, A.V. Sorochinskaja1, A.I. Obzhirov1, G.I. Ivanov2

1 V.I. Ill’ichev Pacific Oceanological Insitute FEB RAS, Vladivostok, 690041, 43 Baltiyskaya Str., Vladivostok, e-mail: [email protected], [email protected], [email protected] The Federal State Unitarian Research and Production Company for Geological Sea Survey (SEVMORGEO), 198295 St. Petersburg, 36 Rosenshtein Str. [email protected]

The regional transect of sub-meridian direction (550 km length, Fig. 1) from the Billings Cape to the Mendeleev Ridge was carried out in the East-Siberian Sea in 2008. Sediment were collected and described and hydrocarbon gas distribution in the subsurface sediments was studied.

The main goal of this research was the gas-geochemical study of the bottom sediments using “head-space” method. Several methane anomalies and other hydrocarbon gases presence were found in the sedi-ments. Gas leakage with methane content of about 2.4% vol. was determined in the central part of the profile. These concentrations are sufficient for the gas hydrates formation. Obtained data characterize basic features of the hydrocarbon gases distribution down the lateral section. Methane content was measured in all gas samples which were collected from the bottom sediments. Measured methane concentrations varied widely from 2.0 ppm to 2.4 %. Methane concentrations increase down the lateral section with the various gradients indirectly indicating gas content in sediments. The high content of methane is revealed along the entire profile. Heavy hydrocarbon gases in the bottom sediments are represented by ethane, ethylene, pro-pylene, propane, butane, and pentane. Ethylene, with the concentrations varying from 0.06 to 80 ppm, was determined practically in all the samples. Ethane was determined in 98% of the studied samples. The highest value of ethane (0.43 ppm) was measured at the station 470 at 90 cm horizon. Propylene with its maximum

Fig. 1 Anomalies of methane in the bottom sediments of the East-Siberian Sea. The diagrams of methane content (ppm) in the sediments are in the logarithmic scale.

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content of 0.61 ppm was determined in all the gas samples. Propane with the maximum value of 0.33 ppm was detected in 70% of the gas samples. Butane is founded in 60% of the studied gas samples mainly at the northern end of a structure. The highest butane content (up to 0.7 ppm) was determined at the station 490 at 65 cm horizon. Pentane with its maximum value of 17 ppm (station 110) was determined at the northern part of a structure.

Near-bottom sediments (0-5 cm beneath seafloor) along the profile were represented by aleurite pelitic, aleurite psammitic and pelite aleuritic (Fig. 2). The coarse-grained material accumulation in sediments is resulted from offshore ablation.

Significant content of pelite at all the stations locating along the profile is explained by subglacial marine settings of sedimentation, which are typical for the East-Siberian Sea. Hereupon, the basic process respon-sible for the sediment accumulation is gravitation settling of clay particles [4].

Concentrations of Corg

in the sediment samples are in the range of 0.29-2.27% and 1.6% in average. The high content of C

org in the subsurface sediment layer testifies the active productive processes in the water

layer and the calm hydrodynamic conditions. These conditions promote an accumulation of argillaceous material and organic remains. Week correlation between C

org and methane contents specifies an insignificant

consumption of the organic material during the gas formation. This allows to assume a mixed origin of the methane in the bottom sediments.

The elemental composition of the subsurface sediments along the entire profile was determined by ICP-MS and ICP-OES methods. The obtained results have shown that the subsurface sediments are enriched with Na (4-8 times), P (1.5-4 times), Fe (1.5 times), Zn (2 times), Ag (1.3-2 times) as compared to the aver-age values of these elements in continental sedimentary rocks [5]. The Rb, Cs, Li, K, Ca, Sr, Ba, U, Th, Mo, Ti, Ga, Tl, Be, Hf, Nb, Zr contents in the sediments are lower than the clarke values.

The alkaline elements (Li, Rb, Cs, and K) were united on the base of their content in the upper part of the continental sedimentary rocks .The increased content of Na indicates its presence in the crystal lattice of hydromica (the main mineral of pelitic fraction) and extraction of the element by phytoplankton [2]. The content of the alkaline elements is controlled by the content of pelitic component.

Fe, Mn, Zn, Cu, Cd, Ni, Co, Cr are known as the organizers of hardly soluble humate complexes [3]. That is why the contents of these elements correlate quite well with C

org. values

A sharp increase of Mn, Cu,

and Cd contents at some stations was found in the uppermost sediments (Fig. 3). Sediments sampled from

Fig. 2 Variation of Corg

and sediment grain-size composition along to the studied profile.

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these stations have the maximal amount of pelitic component (50-70%) and high Corg

content (1.5-2.3%). Moreover, gas anomalies (measured methane content 3-4 times higher than that of its background value) were registered in sediments near these stations. The abovementioned conditions provide diagenetic redis-tribution of Mn. All forms of manganese from Mn to Mn+2 which is high-fluent form of Mn are remobilized due to the organic matter decay. The solid compound of Mn+ is formed due to an inverse process occurring out of the gas anomalies [6]. H

2S is one of the main Cu and Cd nonsolvents producing as a result of the or-

ganic matter decay.The rare-earth elements content measured in the studied sediments was normalized according to the

rare-earth elements in North-American schist (NASC). The rare-earth elements content in the studied sedi-ments correlates well with the contents of С

орг and Fe that is related with sorption of lanthanoids by ferric

hydroxide and organic matter.The silver content in sediments is increased in 1.2-2 times down the profile. One of the reasons of this

is the ability of silver to be sorbed by humic acids (that are natural complexing sorbent for the ions of silver) with production of not readily soluble lignite material complexes [1].

Conclusions1. The results of the gasgeochemical study along with the regional profile from the Billings Cape to-

ward Mendeleev Ridge in the East-Siberian Sea allow to obtain qualitative and quantitative characteristic of hydrocarbon gases distribution in the subsurface sediments. Methane seepage (with methane content of 2.4% vol.) occurrence is revealed in the central part of the profile. The features of general distribution of the hydrocarbon gases are probably controlled by lithology, whereas the methane anomalies are tectonically controlled.

Fig. 3 Mn, Cu, Cd, CH4 distributions in the subsurface sediments.

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2. High Сorg

content in the subsurface sediments (up to 2.3%) reflects active production processes in the water and calm hydrodynamic environment. Weak correlation of С

org and methane contents allows to sup-

pose a mixed origin of methane in the sediments.3. The uppermost sediments studied along the profile are weakened with the most of examined chemical

elements.4. The chemical elements distribution in the subsurface sediments studied along the profile are con-

trolled by the following factors:a) Grain-size composition, variations of psammitic and pelitic components content.b) Organic and mineral complexes production playing an important role in the accumulation of many

elements.c) The presence of the methane anomalies in sediments provides specific physical-chemical conditions

and, therefore, accumulation of some elements (Mn, Cu, Cd).

REFERENcESVarshall G.M., Velyukhanova T.K., Baranova N.N., Koshcheeva I.Ua. et al.1. Complex formation of Ag and humid acids and geochemical significance of this process // Geochemistry. No. 8-9. 1994. P. 1287-1294. In Russian.Dudarev O.V., Botsul A.I., Anikeev V.V. et al. 2. Modern sediment formations in the cryolitic zone of the NW part of Anadir Bay (Bering Sea) // Pacific Geology. 2001. Vol. 20. No. 3. P. 12-25. In Russian.Lisitsin A.P. 3. Marginal filter of ocean. Oceanology. 1994. Vol. 34. No. 5. P. 735-747. In Russian.Pavlidis Yu.A., Shcherbakov F.A. Modern sediments of Eurasion Arctic Seas. Oceanology. 2000. Vol. 40. No. 1. 4. P. 137-147. In Russian.Perel’man A.I. 5. Geokhimiya. Moscow. 1979. 423 p. In Russian.Rosanov A.G., Volkov I.I. 6. Bottom sediments of Kandalaksha Bay of Beloe Sea: manganese phenomena. Geo-chemistry. 2009. No. 10. P. 1067-1085. In Russian.

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MODELiNG OF THERMODYNAMic pROpERTiES AND pHASE EqUiLiBRiA OF MixED METHANE – ETHANE GAS HYDRATES cS-i AND cS-ii

Subbotin O.S.

Nikolaev Institute of Inorganic Chemistry, Novosibirsk, 630090 Russia

The calculations in the framework of molecular level model of phase transformations structure sI- struc-ture sII were performed for binary ethane-methane hydrates with different gas phase compositions taking into account. The conditions of hydrate formation in equilibrium with gas phase and ice are determined at different gas phase compositions and pressures. It was shown that even at very low ethane concentration in the gas phase (about 0.5%) hydrate structure sII becomes more stable than sI.

Regions of stability of mixed hydrate phases sI and sII in T-P plane have been predicted. For mixed hydrates with ethane content about 5% in gas phase we predict pressure-induced phase transformation at low temperatures.

This work has been supported by the Russian Foundation for Basic Research through Grant No. 08-03-00191 and integration project No 62 RAS.

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cHARAcTERiSTicS OF SHALLOw GAS HYDRATE AND RELATiONSHip wiTH cOLD SEEpAGE

Xiwu Luan1, Anatoly Obzhirov2

1 Key Lab of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China2 V.I. Il’ichev Pacific Oceanological Institute of the Far Eastern Branch of Russian Academy of Sciences, Vladivostok 690041, Russia

Multidisciplinary field investigations were carried out in Okhotsk Sea by R/V Akademik M.A. Lavren-tyev (LV) of the Russian Academy of Sciences (RAS), in May 2006 supported by funding agencies from Rus-sia, Korea, Japan and China. Geophysical data including echo-sounder, bottom profile, side-scan-sonar, and gravity core sample were obtained aimed to understand the characteristics and formation mechanism of shallow gas hydrates in Okhotsk Sea. Based on the geophysical data, we found that the methane flare detected by hydroacoustic complex in this cruise was the evidence of free gas in the sediment layer. While the convex structure on the slope imaged by side-scan sonar and bottom profile several hundreds meters in diameter and several tens meters in height was the root of gas venting. Most of the gravity cores were targeted on the convex structures. According to the side-scan image, the size of convex structure is only?) on top of the convex structure may be even smaller. Gravity coring works of this cruise were all targeted on those slope convex structures. Based on the sediment sample we found that free gas commonly exists within the gas hydrate stability zone, and cheese like structure is a special structure due to saturated gas releasing from the sedimentary layer. Two of the gravity cores retrieved gas hydrate sample which was interbedded as thin laminae, and lenses with thickness varying from a few millimeters to 3 cm. Gas hydrate content in hydrate-bearing intervals visually amounted to 10-80% of the sediment volume. But small gas hydrate pellets still could be found within the sedimentary grain when took a close look. More gas hydrate cells that can’t be seen visually by eyes might still exist in the sedimentary pores. Gases in the sediment core are not all from gas hydrate decomposition during the gravity core lifting. Free gases must exit in the gas hydrate stability zone. Tectonic structures like mud volcano, mud diaper and convex structure in this paper are free gas central. Gas hydrate formed only when gases over saturated in this special structures. Out side this structures gas hydrate might not formed due to low gas concentration. Sulfide-methane interface also controlled the gas hydrate formation. Gravity core can’t sample gas hydrate above the sulfide-methane interface.

Modeling work results show that cold seepage provides benefit condition for the gas hydrates formation not only for sufficient methane supply but also for a favorable temperature and pressure conditions.

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GEOcHEMicAL AND MicROBiOLOGicAL cHARAcTERiSTicS OF SEDiMENTS NEAR THE MALENKY MUD vOLcANO (LAKE BAiKAL,

RUSSiA), wiTH EviDENcE OF ARcHAEA iNTERMEDiATE BETwEEN THE MARiNE ANAEROBic METHANOTROpHS ANME-2 AND ANME-3

Zemskaya T.I.1, Pogodaeva T.V.1, Shubenkova O.V.1, Сhernitsina S.M.1, Dagurova O.P.2, Buryukhaev S.P.2, Namsaraev B.B.2, Khlystov O.M.1, Egorov A.V.3, Krylov A.A.4, Kalmychkov G.V.5

1 Limnological Institute, SB RAS, 3, Ulan-Batorskaya St., Irkutsk, 664033, Russia, e-mail: [email protected] Institute of General and Experimental Biology, SB RAS, Ulan-Ude, Russia3 Institute of Oceanology, RAS, Moscow, Russia4 VNIIOkeangeologia, St.-Petersburg, Russia5 Vinogradov Institute of Geochemistry, SB RAS, Irkutsk, Russia

Detailed lithological, biogeochemical, and molecular biological analyses of core sediments collected during 2002-2006 from the Malenky mud volcano (Lake Baikal) are revealed considerable spatial varia-tions in pore water chemical composition with total concentrations of dissolved salts varying from 0.1 to 1.8‰. Measured values of δ13С methane in the sediments suggest its biogenic origin (δ13Сmin -61.3‰, δ13Сmax -72.9‰). The rates of sulphate reduction varied from 0.001 to 0.7 nmol cm-3day-1, of autotrophic methanogenesis - from 0.01 to 2.98 nmol of CH

4 cm-3day-1, and of anaerobic methane oxidation - from 0

to 12.3 nmo cm-3day-1. These results indicate that methane generation is the dominating processes in gas hydrate-bearing sediments of Lake Baikal. Based on clone libraries of 16S rRNA genes amplified with Bac-teria- and Archaea-specific primers, investigation of microbial diversity in gas hydrate-bearing sediments reveals bacterial 16S rRNA clones classified as Deltaproteobacteria, Gammaproteobacteria, Chloroflexi, and OP11. Archaeal clone sequences are related to the Crenarchaeota and Euryarchaeota. Baikal sequences of Archaea form a distinct cluster occupying intermediate position between the marine groups ANME-2 and ANME-3 of anaerobic methanotrophs.

This work was supported by the Russian Foundation Basic Research program No 08-05-00709, Integra-tion Project SB RAS No. 27 and Presidium Program RAS, Project 20.9.

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