Veins He Den Quist

7/31/2019 Veins He Den Quist

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Epithermal Au-Ag vein deposits:

Critical characteristics, variations, and exploration

Ares, January 2005

Jeffrey W. Hedenquist Ottawa, Canada

Epithermal vein deposits Terminology: metal variation

Background: features, variations and causes

LS deposits: Back-arc

IS deposits: Intrusion-centered (vs Mexican)

Exploration

Zacatecas, Mexico

Epithermal types:Alternative terminologyLargely synonymous

Type 3 Type 2 Type 1

Gold (Te, Se)-qtz veins Ag, bms veins Goldfield type, Au-al, 2nd qtzite 1903-33

Alkaline epithermal Acid epithermal 1977

- - - - Epithermal - - - - - 1981

Hot spring Au-enargite 1982

Adularia-sericite, low sulfur Acid sulfate, high sulfur, al-kaol 1986-89

Low sulfidation High sulfidation 1987

Low sulfide/bms, High sulfide/bms, High sulfidation 1991, 93

Type 2 ad-ser Type 1 ad-ser

Bimodal basalt-rhyolite Western andesite High sulfidation 1999, 01

Low sulfidation (LS) Intermediate (IS) High sulfidation (HS) 2000, 03

LS, LSa (alkalic) IS zoned, IS Mex HS, HS-IS zoned evolving

Ransome, Emmons, Lindgren, Nakovnik, Sillitoe, Buchanan, Ashley, Giles, Bonham,

Bethke, Heald et al., Berger, Albino, John, Hedenquist et al., Einaudi et al.

Examples of epithermal deposits

LS veins:Midas, Sleeper, Mule Canyon, Lewis-Crofoot; El Limn;

Beroen; Ares?; El Pen; Cerro Vanguardia, Esquel; Hishikari; Balei

LS veins, alkalic: Cripple Creek, Emperor, Porgera, Ladolam

IS veins:Comstock, Creede; Tethys, e.g., Rosia Montana,

Sacarimb; Victoria, Baguio, Philippines (adj. lithocaps); Toyoha, Sado,

Kushikino, Japan; Kelian; Arcata, Orcopampa, Cordilleran, e.g.,

Julcani, Colqui & Quiruvilca (w/ HS), all of Per, ; vs. Mexican

Ag:Au:bms, e.g., Tayoltita, El Oro, Guanajuato, Pachuca, Fresnillo,

Zacatecas

HS replacements:


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Metal Budgets: Function of salinity and volcanotectonics

LS Au-Ag:


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Temperature-dependentalterationmineralogy

LS deposits: sulfide assemblages

LS veins: AuAg, bonanzas

Pyhigh-Fe sph asp or po,

Se or Te

Distinctly related tovolcanotectonic setting

Barton et al., 1977, John, 2001,Einaudi et al., 2003, others

IS and HS deposits: sulfide assemblages

IS veins: AgAu PbZn

Pylow-Fe sphtn/tdccpgn, Te (Bi, Sn, In)

HS replacements: Cu-Au-Ag

Initial leaching, vuggy qtz-py

Early pyenargitelz-fm

Late Aulow-Fe sph

tn/tdccpgn, Te-Bi-Sn

Einaudi, Hedenquist and Inan, 2003

Sulfidation states


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Einaudi, Hedenquist and Inan, 2003

Sulfidation stateevolution

Wallrock

buffe

r

HS IS LSHS IS LS

Ya

RMt

Hedenquist et al., 2000

Vi To

Sillitoe and Hedenquist, 2003Low sulfidation vein setting

Champagne Pool,Waiotapu, NZ


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Lewis-Crofoot, NV:LS veins, steam-heated overprint (falling water table)(NB: remnant qtz veins + Au within overprinted zone)

Sulphur, NV, near paleosurface

Low-sulfidation schematic model

Hedenquist et al. (2000),modified from Buchanan

(1981), Sillitoe (1993)

McLaughlin, CA:LS sheeted veins beneathsinter with Hg

McLaughlin, CA:Atypical LS host

Sherlock et al. (1995)


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Hydro-thermal

brecciawith

sinter

Sheeted

vein


Mineral deposition in

conduits, pressureincreases above

hydrostatic, hydraulic

fracturing, and

hydrothermal eruption:

mineral (+Au) deposition


LS epithermal veins:

Extreme disequilibrium

Rapid ascent

Rapid boiling

Rapid cooling

Rapid supersaturation, silica, Au

Exploration implications Extensional setting, fault offsets

cf. Saunders 1994;

Saunders et al., 1996;

Sillitoe and Hedenquist,

2003

Sleeper banded ore: Au dendrites Hishikari, S Kyushu


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Hishikari, S Kyushu

>8 Moz AuHishikari,

S Kyushu:Geological and

geophysicaldiscovery,

LS veins in

greywacke

basement

Izawa et al., 1990

500 m

Hishikari, S Kyushu

Paleoisotherm reconstruction

Izawa et al. (1990)

Hishikari long section

Izawa et al. (1990)


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Zuisen vein, -10 mL

late truscottite

Patagonia, ArgentinaMidas, NV:Ken Snyder LS mine

from Goldstrand and Schmidt, 2000


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Ken Snyder mine: Long section

300 m


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Surface projections:

Lepanto,

Far Southeast

and Victoria

From Palidan slide

Hedenquist et al. (2001) Claveria (2001); Hedenquist et al. (2001)


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Arribas et al. (1995); Sajona et al. (2001); Claveria (2001); Hedenquist et al. (2001)

Surface projection of Lepanto

HS, Far Southeast porphyry,and Victoria-Teresa IS vein

ores, and ages

Hedenquist et al. (2001)

Teresa

veins

Bulalacao ?porphyry

X Biot

1.18 Ma

X Horn1.45 Ma

Hydro Biot

1.40-1.45 Ma

Alunite1.40-1.45 Ma

X Illite

1.15 Ma

Ser ~1.35 Ma

Bt 2.2-1.8 Ma

HS IS LSHS IS LS

Ya

RMt


Vi To

Kyushu epithermal deposits: LS and IS veins

Metallogenicprovinces inKyushu

Type, age andgeology ofepithermal Audeposits

Tectonicinterpretation

Y. Watanabe (2004)


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Au provinces in KyushuY. Watanabe (2004)

Volcanic setting of Kushikino IS deposit, Kyushu

(Izawa and Zeng, 2001) 55 t Au production

Kamuridake, capped by silicic zones

Kushikino veins (insets), 2 - 4 km west Temperature-

dependent

epithermal

alteration

mineralogy

compiled byHedenquist et al. (1996)


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Arcata, Per: IS Ag-Au vein:~100 Moz Au, 1 Moz Au (local Zn)

adv. argillic vein halo at surface

Arcata, Per:IS Ag vein: qtz-rhodochrosite

after Candiotti et al. (1990)

Comstock Lode, NV

6000 t Ag, 257 t AuCon Virginia: 1.13 Mt @

87.4 g/t Au, 1834 g/t Ag

Hudson (2003)

Propylite: Richthofen, BeckerAd: 12.7-14.1 Ma, Al: 15-16.3 Ma

SH

Al to

pyrop

diasp

to

kaol

dick

to

illite

2 km

2M mica


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ComstockLode:Ag-Au ISbonanzaveins; longsection plusreconstructionpre-faulting(?), with Slateral flow

Vikre (1989), flincs,

Hudson (1993, 2003)

500

m

1 km

Bartos (1987)

1 km

inner stib

outer tn-td

outer en

Quiruvilca, Peru:

Zoned IS bms vein systemProd. 1987, 8 Mt: Reserves 5.8%Zn, 2.0% Pb, 2.8% Cu, 230 g/t Ag

Alto Chicama

~5 km east

Calipuy Fm

Sillitoe and Hedenquist (2003),

modified from Einaudi et al. (2003)IS vein deposits

Principle IS deposits: Ag-Au (Zn-Pb, Cu)

Simple sulfide mineralogy & gangue: Mexico

Complex sulfides/sulfosalts, zoned: intrusion related

Up to many km long and 800 m vertical

Tops and bottoms not uniform

Common on margin of HS deposits (barren lithocaps?):

associated w/ adv. arg. alteration

Typically small (Rodalquilar, Rio del Medio at El Indio), but

exceptions (Victoria-Teresa)


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Zacatecas, Mexico: IS veins with multiple pulses of saline fluidMexican Ag-Au bms veins:

Depth below paleosurface and

Au:Ag:bms relationship

Albinson et al. (2001)

Pachuca, Mexico: IS vein and fault pattern

45,000 t Ag, 220 t Au

Simmons et al. (2005)

after Geyne et al. (1963)

4 km

Pachuca fractures, dikes, ore, surface alteration

Wisser (1948)

2360 m datum


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Pachuca:

Cross and long sections

Drier, 1982

Geyne et al., 1963

500

m

from Simmons et al.

(2005), with permission

HS IS

LS IS

10 km

Creede IS

from Simmons et al.(2005), with permission

2 km

LSa LSLSa

HSLSaIS


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from Simmons et al.

(2005), with permission

1 km

HS w/ IS to N

LS

IS w/ lithocap

IS w/ adv arg

HS

LS

LSa, VIILS

Sillitoe and Hedenquist (2003)

Schematic relations: HS and IS epithermal deposits,

and porphyry systems

+

+ +

+

Fresnillo, Mexico: Major IS deposit, Ag-Au veins

13,600 t Ag, 22 t Au

Co. ProaoSan Luis shaft Simmons et al. (1988)

Sillitoe (1977)

10 kt Ag, 18 t Au, 0.5 Mt Zn, 0.5 Mt Pb

Ag

bms

Low salinity(buoyant)

Higher salinity(dense)

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