Ore Geology Reviews 47 (2012) 1–4

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Ore Geology Reviews

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Preface

Manganese metallogenesisIntroduction to the special issue

Research into the origin and distribution of manganese deposits hasalways occupied a small but important niche in economic geology. Ofparticular value for the progress achieved in manganese depositresearch was a succession of programs funded by the InternationalGeological Correlation Programmes (IGCP). Through six of these IGCPprojects international research collaboration was effectively supportedfrom 1975 until 2002 (Table 1). These programs enabled a large num-ber of scientists and postgraduate students from various continentsand countries to interact with one another. Manganese ore depositsworldwide were investigated during field workshops and resultswere presented at numerous international conferences.

Results of such international research programs were alsopublished in several books and journal special issues. These include: Geol-ogy and Geochemistry of Manganese I, II, III (IGCP 111; Varentsov andGrasselly, eds., 1980); Manganese Deposits (IGCP 111; Roy, 1981);Manganese Metallogenesis and Metallogenesis of Manganese (IGCP226; Bolton ed., as Special Issues of Ore Geology Reviews, 1988, 1990); ASpecial Issue on Manganese Metallogenesis (IGCP 226; Bolton ed., asSpecial Issue of Economic Geology, 1992); Precambrian tomodernmanga-nese mineralization: changes in ore type and depositional environment(IGCP318;Nicholson et al., eds., 1997);Manganese and associated orede-posits of China (IGCP 226 and 318; Hein and Fan, eds., as Special Issue ofOre Geology Reviews, 1999); and Manganese Ores of Hungary (IGCP 111,226, 254, 318, 357, 429; Polgári et al., eds., 2000). These volumes arecomplemented by a large number of peer-reviewed journal papers andbook chapters. Despite this success, no international collaborationprogram has come into existence to support research into the origin ofmanganese deposits since the end of IGCP 429 in 2002.

As national chair persons and members of working groups theGuest Editors of the present special issue benefitted greatly fromseveral of these IGCP programs. The international short course inVeszprém in 2009 was organized not only in an attempt to revive inter-est in manganese research, but also to celebrate the 20th anniversary ofan international workshop of IGCP 226 that was held in Úrkút, Hungary(Fig. 1). Twenty years on, the international workshop “Manganese in theXXI. Century” featured many of the original lecturers, internationallyleading experts in the field of Mn deposit research (Fig. 2).

The contributions presented in this special issue reflect the diversityof geological environments, and associated mineralogical and geo-chemical complexity, typically associated with manganese deposits.Nicholson et al. (1997) stressed that this variability reflects “differencesin the processes of formation and depositional environments, which inturn are a response to change in the land–ocean–atmosphere systemover geological time. As much, manganese deposits can act as markersof major events in the dynamic evolution of the Earth's surface.” The

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contributions included in this volume focus on the origin of stratiformand stratabound manganese deposits ranging in age from the Paleo-proterozoic to the late Mesozoic and Tertiary. Manganese accumulationin various geological environments are considered.

The first two contributions in this volume concern the originof manganiferous and ferruginous sedimentary rocks of Devonianage in the Urals (Russia). The origin of proximal manganese- andiron-rich precipitates closely associated with VMS systems are con-sidered in the paper by Maslennikov et al. (2012-this issue). Bycareful analysis of textural, mineralogical and geochemical character-istics the authors reveal the importance of halmyrolysis (i.e., post-sedimentary but pre-diagenetic) replacement processes for the originof jaspers, jasperites, gossanites, and umbers. The proposed processesof halmyrolysis followed by silicification, in situ, may resolve theenigma of silica-rich sediment formation in a silica undersaturatedocean.

A second contribution (Brusnitsyn and Zhukov, 2012-this issue),collates and reviews the results of comprehensive studies of about100 occurrences and deposits of Paleozoic jasperite and jasper, andhydrothermal–volcaniclastic–sedimentary manganese deposits notassociated with known VMS deposits of the Southern Urals regions(Magnitogorsk paleovolcanic belt). Manganese ores associated withjasperites in this belt are identified as deposits localized at hydrother-mal discharge zones. Thin-banded jasper occurrences, in contrast, rep-resent distal formations formed under a decreasing influence ofseafloor hydrothermal systems. Mineralogical complexity (>70 differ-ent minerals identified) in these iron- and manganese-rich precipitatesis attributed to diagenetic and low grade regional metamorphism(T≈200–260 °C, P=2–3 kbar). The presence and abundance of organ-ic matter (OM) deposited with the ferruginous andmanganiferous pre-cipitates are identified as a critical parameter to determine theresponse to postdepositional alteration as a oxide–carbonate–silicate(“reduced”) mineralogical facies (high primary OM content), whichcan be distinguished from a oxide–silicate (“oxidized”) mineralogicalfacies (low primary OM content).

Black shale-hosted Mn carbonate deposits represent distal environ-ments in the sense of metal source. There is typically a lack of geologicalevidence for the genetic association of such depositswith hydrothermalfluid flow.Nevertheless, hydrothermal fluids are often thought to be theultimate metal source for this economically very important deposittype. The origin of black shale-hosted manganese deposits has longremained contentious, in particular since high-grade manganese oxideores exploited from such deposits were derived by lateritic weather-ing—with metasedimentary manganiferous protoliths discovered onlymuch later. An important example for this deposit type is the Serra do

Table 1IGCP programs that had an important impact on manganese research.

Project No. Duration Title

111 1975–1985 Genesis of manganese ore deposits226 1986–1990 Correlation of manganese sedimentation to

paleoenvironments254 l987–1991 Metalliferous black shales318 1991–1995 Genesis and correlation of marine polymetallic

oxides357 1993–1997 Organics and mineral deposits429 1998–2002 Organics in major environmental issues

2 Preface

Navio deposit in the Amapá Province, Brazil (Chisonga et al., 2012-thisissue). Based on a detailed petrographic and geochemical study theauthors decipher the architecture and history of this deposit andpropose a comprehensive metallogenetic model. This model predictsdeposition of manganese (Mn4+ oxyhydroxide precipitates) andclosely associated chert in intra-arc basins, in environments thatwere bypassed by distal siliciclastic (carbonaceous mud) and proxi-mal pyroclastic/siliciclastic detritus. Mn carbonates then derived duringsuboxic diagenesis. Metamorphic alteration of manganese carbonate–chert assemblages resulted in the formation of Mn-silicates (1–2 kbarand 400–500 °C, upper greenschist facies). It is this metamorphosedsuccession that sourced the high-grade manganese oxide ores duringprolonged lateritic weathering.

Economically important black shale-hosted manganese carbonatedeposits also occur in certain parts of the Transdanubian Range inHungary. In his contribution, Haas (2012-this issue) provides asummary and critical review of factors that had an important bearingon the origin of these deposits at different scales. The deposits wereformed in a short interval coinciding with the Early Toarcian (Jurassic)global anoxic and mass extinction event that was associated with dras-tic perturbations of the oceanographic conditions. Simultaneous open-ing of two neighboring ocean basins created an extensional regimeresulting in a complex topography with tectonically-controlled small

Fig. 1. Group photo of participants of Manganese Workshop (IGCP 226) at Úrkút, Hungary(Hungary, Úrkút mine), Gyula Grasselly (Hungary), Andrea Mindszenty (Hungary), SuprSzabó (Hungary, Úrkút mine), Yu Hariya (Japan).

scale basins above an attenuated continental lithosphere. Only togetherthese different favorable circumstances facilitated the deposition (andpreservation) of this important manganese deposit.

Polgári et al. (2012-this issue) place further constraints on thismodel for the manganese deposits of the Transdanubian Range byestablishing the importance of microbial processes. In a first step,aerobic chemolithoautotrophs facilitated the efficient oxidation ofMn(II) and the precipitation of Mn(IV) oxyhydroxide proto-ores.The aerobic initial lithoautotrophic microbial step is followed by asyndiagenetic anaerobic heterotrophic bacterial cycle that resulted inthe formation of the Mn(II) carbonates that now predominate themineralogy of the Úrkút deposit. It is essential to note that this modelrequired oxygenated bottom water conditions during sedimentation,illustrating that black shale-hosted Mn-carbonate deposits may be animportant paleoenvironmental indicator. Although some of a numberof the black shale-hosted Mn-carbonate deposits are of biogenetic–bacterial sedimentary origin, a hydrothermal/exhalative source ofmetals may have contributed to their formation. An Fe–Mn-oxidechimney system is proposed to be a proximal facies to geofluid ventsthat occurred along fracture systems, which may have provided metalsfrom deep-seated sources. It is suggested that a similar microbialgenetic model may be applicable to many other black shale-hostedmanganese deposits.

Different to the two papers above, Sinisi et al. (2012-this issue)illustrate the complexity of manganese mineralization formed by lowtemperature hydrothermal fluids in a synsedimentary shallow marineshelf environment or, alternatively, in a diagenetic terrestrial environ-ment. This study, in particular, demonstrates the particular difficultiesassociated with identifying the exact genetic history especially ofstratabound manganese deposits.

The final two contributions to this special issue are dedicated tounderstand and quantify the effects of fluid induced alteration onmanganese ores of the giant Kalahari Manganese Deposit, South Africa.The effects of hydrothermal alteration on the geochemistry and miner-alogy of sedimentary manganese carbonate ores are documented by

, 1989. From left: Vasilis Galanopoulos (Greece), James R. Hein (USA), Zoltán Kovácsiya Roy (India), Barrie R. Bolton (Australia), Nicolas J. Beukes (South Africa), Zoltán

Fig. 2. Group photo of participants of Manganese in the XXI. Century Course in Veszprém, 2009. From left: Zoltán Sas (Hungary), Borbála Máté (Hungary), Uroš Herlec (Slovenia),Tamás Vigh (Hungary, Úrkút mine), Tamás G. Weiszburg (Hungary), Jens Gutzmer (Germany), Igor G. Zhukov (Russia), Nicolas J. Beukes (South Africa), Márta Polgári (Hungary),János Haas (Hungary), Nuriya R. Ayupova (Russia), Edward P.W. Swindell (South Africa), Lóránt Bíró (Hungary), Sarolta Bodor (Hungary), Alexandra Müller (Hungary), ZoltánSzabó (Hungary, Úrkút mine), James R. Hein (USA), Susanna B. Muiňos (Portugal), Barrie R. Bolton (Australia).

3Preface

Chetty and Gutzmer (2012-this issue) for an example in the Nchwan-ing–Gloria mining area of the northern Kalahari Manganese Deposit.Pronounced mineralogical and major element alteration was impartedon the sedimentary manganese ores by a structurally-controlled hy-drothermal fluid flow event. Hydrothermal alteration results in residu-al enrichment and a much larger scatter in REE contents. A small Ceanomaly observed in the protolith remains similar in magnitude whenobserved in PAAS-normalized REE plots. The data define, however, apower trend in the (Ce/Ce*) vs (Pr/Pr*) diagram. Such behavior is inter-preted in terms of a conservative system that was predominantlyprotolith-buffered. Local remobilization of REE during hydrothermal al-teration is attributed to the dissolution of diagenetic apatite and redis-tribution of hydrothermal trace minerals, including neoformedapatite, monazite and cerianite.

In contrast, Gutzmer et al. (2012-this issue) apply 40Ar/39Ar geo-chronology to document the slow progression of the chemical weath-ering front from the Cenozoic Kalahari Unconformity into thecarbonate-rich manganese ores of the Kalahari Manganese Deposit.Chemical weathering results in complete oxidation and conversionof the low grade diagenetic mineral assemblage dominated by fine-grained kutnahorite and braunite into a high grade ore comprisingessentially of microcrystalline todorokite and manganomelane. Datingof small particles of such supergene enriched ore down the weatheringprofile yields successively younger ages, with oldest age steps of 42 Marecorded immediately below the Kalahari Unconformity. This approachyields an overall rate of downward progression of the weathering pro-file of only 10 cm/Ma. This confirms the long-lived nature of the Africanland surfaces.

Summarizing these aspects and internal relationships it becomesapparent that the study of manganese deposits has the potential toyield further important clues for our understanding of System Earthat different scales and in different eras of Earth History. Of particular

importance is the appreciation of the profound impact of geomicrobio-logical processes on the formation of ore deposits in the sedimentaryand supergene realm, a lesson certainly not limited to manganese de-posits. We hope that this special issue will foster a wider appreciationfor and understanding of the complexity of processes that influencethe composition and distribution of manganese deposits.

Sponsorship for this special issue has been kindly provided by BHPBilliton Ltd. The editors would like to extend our sincere gratitude toEdward (Ed) P.W. Swindell, Mineral Resources Manager, Manganeseof BHP Billiton/Samancor Manganese, South Africa, for offering thissupport. Every paper included in this special issue has been reviewedby at least two international referees. The guest editors and authorssincerely acknowledge the efforts of these reviewers, who each kindlyprovided helpful comments and constructive criticism. Refereesincluded (in alphabetical order): Brian Alexander, Russell H. Bailie,Barrie R. Bolton, Gerald van den Boogaart, Bernd Buschmann, SomnathDasgupta, Thomas Kuhn, Barry J. Maynard, Joydip Mukhopadhyay,József Pálfy, Bernhard Pracejus, Gerd Rantitsch, Carlos Rosiere, HennieTheart and Harilaos Tsikos.

Last but by no means least the guest editors acknowledge the helpof Nigel Cook, Editor in Chief of Ore Geology Reviews, as well as staff ofElsevier, namely Frank Wang, George Vleeming, Ronald Buitenhuis,Jetske Roodvoets, Pablo Labbé, Brian Villegas, Liz Wang, Shannon Quand in particular Hemalatha Moorthy and Katherine Eve.

References

Bolton, B.R. (Ed.), 1988. Manganese Metallogenesis: Ore Geology Reviews, 4, pp. 1–170.Bolton, B.R. (Ed.), 1990. Metallogenesis of Manganese: Ore Geology Reviews, 5, pp.

255–384.Bolton, B.R. (Ed.), 1992. A Special Issue onManganese Metallogenesis: Economic Geology,

87, pp. 1207–1440.

4 Preface

Brusnitsyn, A.I., Zhukov, I.G., 2012. Manganese deposits of the Devonian Magnitogorskpalaeovolcanic belt (Southern Urals, Russia). Ore Geol. Rev. 47, 42–58 (this issue).

Chetty, D., Gutzmer, J., 2012. REE redistribution during hydrothermal alteration of oresof the Kalahari Manganese Deposit. Ore Geol. Rev. 47, 126–135 (this issue).

Chisonga, B.C., Gutzmer, J., Beukes, N.J., Huizenga, J.M., 2012. Nature and origin of theprotolith succession to the Paleoproterozoic Serra do Navio manganese deposit,Amapa Province, Brazil. Ore Geol. Rev. 47, 59–76 (this issue).

Gutzmer, J., Du Plooy, A.P., Beukes, N.J., 2012. Timing of supergene enrichment of low-grade sedimentary manganese ores in the Kalahari Manganese Field, South Africa.Ore Geol. Rev. 47, 136–153 (this issue).

Haas, J., 2012. Influence of global, regional, and local factors on the genesis of the Jurassicmanganese ore formation in the Transdanubian Range, Hungary. Ore Geol. Rev. 47,77–86 (this issue).

Hein, J.R., Fan, D.L. (Eds.), 1999. Manganese and associated ore deposits of China: OreGeology Reviews, 15, pp. 1–176.

Maslennikov, V.V., Ayupova, N.R., Herrington, R.J., Danyushevskiy, L.V., Large, R.R.,2012. Ferruginous and manganiferous haloes around massive sulphide depositsof the Urals. Ore Geol. Rev. 47, 5–41 (this issue).

Nicholson, K., Hein, J.R., Bühn, B., Dasgupta, S. (Eds.), 1997. Manganese Mineralization:Geochemistry and Mineralogy of Terrestrial and Marine Deposits. : GeologicalSociety Special Publication, 119. The Geological Society, London. 370 pp.

Polgári, M., Szabó, Z., Szederkényi, T. (Eds.), 2000. Manganese Ores in Hungary. HungarianAcademy of Sciences. Juhász Publishing House, Szeged. 675 pp. (in Hungarian withEnglish summary).

Polgári, M., Hein, J.R., Vigh, T., Szabó-Drubina, M., Fórizs, I., Bíró, L., Müller, A., Tóth, A.L.,2012. Microbial processes and the origin of the Úrkút manganese deposit, Hungary.Ore Geol. Rev. 47, 87–109 (this issue).

Roy, S., 1981. Manganese Deposits. Academic Press, London. 458 pp.Sinisi, R., Mameli, P., Mongelli, G., Oggiano, G., 2012. DifferentMn-ores in a continental arc

setting: geochemical and mineralogical evidence from tertiary deposits of Sardinia(Italy). Ore Geol. Rev. 47, 110–125 (this issue).

Varentsov, I.M., Grasselly, Gy (Eds.), 1980. Geology and Geochemistry of Manganese,Volumes I, II and III. Akadémiai Kiadó, Budapest. 463 pp., 513 pp., 357 pp.

Márta PolgáriInstitute for Geochemical Research,

Hungarian Academy of Sciences,Budaörsi str. 45.,Budapest 1112,

HungaryE-mail address: rodokrozit@gmail.com

Jens GutzmerDepartment of Mineralogy,

Technische Universität Bergakademie, Freiberg,09596 Freiberg, Saxony,

Germany

31 March 2012