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EPITHERMAL GOLD-SILVER DEPOSIT MODEL

CSA Australia Pty Ltd

CSA

Geological Consultants

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Redrawn and adapted from Hedenquist, Izawa, Arribas & White (1996)*

POSTER

Volcanic Centre 500°- 900° SO2 , HCl, CO2

Low sulphidation Au,Ag epithermal vein deposit

High sulphidation Au,Cu epithermal deposit

Crater Lake Acidic fluid

100° CO 2 , H 2S

Fumeroles

Hot springs

200°- 300° CO 2, HCl, S

200° ng 300°

20 0°

i li Bo ne Prim u tr ali ary sa tio n

Pb/Zn/Ag/Mn mantos

LEGEND Porphyry Cu (Mo,Au) deposit

Saline magmatic fluid Liquid flow

Limestone

300°

Vapour ascent

Porphyries

600°

Fault

1 km Approx

Schematic Cross Section of Volcano-Hydrothermal System RARE

Ore Minerals Quartz

Chalcedony Adularia Illite Calcite Smectite

NEVER

Selenides Stibnite Cinnabar Enargiteluzonite Tennantite Covellite

Barite Kaolinite

ALWAYS

Ore Minerals

Electrum Native gold Chalcopyrite Sphalerite Galena Tetrahedrite Arsenopyrite Tellurides Pyragarite

Pyrite

Gangue Mins

COMMON

Pyrophyllite Diaspore Alunite

Gangue Mins

ALWAYS

COMMON

Native gold Pyrite Tellurides EnargiteCovellite luzonite Tennantite Tetrahedrite Chalcopyrite Sphalerite Galena Quartz

Barite Alunite Kaolinite Pyrophyllite Diaspore Illite

RARE

NEVER

Electrum Selenides Pyragarite Arsenopyrite Cinnabar Stibnite

Chalcedony Smectite

Calcite Adularia

Mineral Abundance in Gold-Rich Systems High sulphidation

Low sulphidation Shallow

Neutral pH, Reduced Smectite Illite±Smectite Illite±Adularia

Deep

Veins

CSA Australia © 2002

Propylitic

Steam-heated Overprint Cristobolite - kaolinite - alunite Kaolinite±Smectite

Acidic, Oxidized Smectite Kaolinite -Alunite Illite±Smectite Propylitic

Alteration Schematic

Vuggy Quartz

Illite Patchy *Spec. Publ. No.1 of Soc. of Resource Geology