Volcanogenic massive sulfide (VMS) deposits

= VMS V olcanogenic M assive Sulfide

• - , - , - Volcanic associated volcanic hosted volcano sedimentary massive sulfides

• ( ; -Associated with volcanics mafic to felsic usually calc) ( ) alkaline and sediments siliciclastics in different

proportions

• Stratabound to stratiform tabular lenses accumulated in ( . . , , , , , , , )massive sulfides e g Py Ccp Asp Po Sp Gn sulfosalts

• : , , , , ( ), , , , , , , Polymetallic Cu Zn Pb Ag Au major Co Sn Se Mn Cd In, , , , , , ( )Bi Te Ga Ge As Sb Hg minor

• ( ) Hydrothermal origin hydrothermal fluids

• + = VMS SEDEX Massive sulfide deposits by hydrothermalfluids

• ( )Of all ages Precambrian to Phanerozoic

• Related to major ocean closing and terrane accretion events

• : (“ Modern equivalents Hydrothermal vents on seafloor Black”) Smoker

. .www whoi edu

General features

“ ” , Black smoker on seafloor submersible Alvin

General features

+ , Zn Pb– Cu

, Lydon 1984

Additional phases

•Pyrrhotite• Barite•Magnetite•Arsenopyrite•Bornite•Mackinawite• ( )Sulfosalts Tennantite etc•Tellurides• , Acanthite Argentite

Classifications I

- Host rock lithology

) - ( )6 High sulfidation bimodal felsic epithermal

Ø ( ) /Predominantly mafic volcanics tholeiitic basalts with minor sediments ultramafics

Ø - , Cu rich smallØ ( ), - Ocean ridge ophiolites back arc riftØ ( - ) Predominantly mafic volcanics tholeiitic to calc alkaline basalts

with minor felsic volcanics and subordinate sedimentsØ -Cu richØ( ) rifted primitive volcanic arcØ / ≈ , ± Mafic volcanics intrusives turbiditic sediments felsic volcanic absentØ , Sedimented oceanic rift rifted continental margin

Ø - ( ) Predominantly calc alkaline felsic volcanics rhyolite with minor mafic / volcanics felsic intrusives and subordinate sedimentsØ - , ± Highest Zn content on average bariteØ ( ) Compositionally rifted volcanic arc

) ( - )1 Mafic Cyprus type

) - ( - )2 Bimodal Mafic Noranda type

) - ( - )3 Mafic Siliciclastic Besshi type

) - ( - )4 Bimodal Felsic Kuroko type

) -5 Bimodal Siliciclastic

Ø ([ - ] > [ ] ) ≈ Volcanics calc alkaline felsic tholeiitic mafic siliciclastic rocksØ -/ - Highest Pb lowest Cu content on averageØ Greatest tonnage and largest size on averageØ( ) rifted continental arcØ - Characteristic similar to bimodal felsic group

Ø , ( , )Besides sulfides sulfosalts tetrahedrite stanniteØ (‘ ’ )Epithermal conditions hybrids of VMS and epithermal depositsØ -Shallow back arc

. ( )Galley et al 2007

, Decrease

inCu

Increasein

Pb

Primitiv eto

“”

maturesetting

Increasein

/size

ton nage

- Host rock lithology

) ( - )1 Mafic Cyprus type

) - ( - )2 Bimodal Mafic Noranda type

) - ( - )3 Mafic Siliciclastic Besshi type

) - ( - )4 Bimodal Felsic Kuroko type

) -5 Bimodal Siliciclastic

Increasein

SiO2

ofhost

rock

Classifications I

., ; , Franklin et al 1981 Large 1992

Classifications II

Base metal classification

• (- )Cu Zn

• -Zn Cu

• - -Zn Pb Cu

• - ( )Pb Zn SEDEX

World VMS( modified after

, )Franklin 1996

Classifications II

Base metal classification

• (- )Cu Zn

• -Zn Cu

• - -Zn Pb Cu

• - ( )Pb Zn SEDEX

., Galley et al 2007

World VMS( modified

after, Franklin

) 1996

Canadian VMS

Tectonic setting

., Galley et al 2007

General model

, Franklin 1993

Summary

What?

Where?

How and why?

Ø , ( ) Polymetallic stratiform deposits associated with volcanic mafic to felsic / and or siliciclastic rocks in different proportionsØ Massive sulfide lense with mineral zonation

Ø : Today Spreading ridges and arc settingsØ : Geologic record Primitive to more compositionally mature volcanic arc ( ), ( ) , , fore to back arc rifted continental arcs shallow back arcs and ( , )spreading ridges ophiolite minor

Ø ( ° ) Circulation of hot up to 400 C hydrothermal fluids within crustØ Interaction with cold seawater and cold wall rockØ - Precipitation of massive sulfides due to physico chemical processes ( . ., , , )e g ∆T ∆pH redox state