porphyry transitions anti ago

8/2/2019 Porphyry Transitions Anti Ago

1/20

Sakurajima, Kyushu: ionized gases Bingham Canyon, Utah: >31 Mt Cu!

Sociedad Geolgica de Chile: July 2011

Adv. argillic?

Bingham porphyry, Utah

Redmond et al., 2004

80% 20%


2/20

Diorite intrusion: if X magmatic fluid advected,

intrusion heat convects ~19X meteoric water

Extreme hydrolytic = advanced argillic

Na-Ca basinbrines

F - feldspar stable (potassic)

H - hydrolytic (attack by H+)

(phyllic and advanced argillic)

E - caused by external fluids

(propylitic and sodic-calcic)

propylitic

Lowell and Guilbert, 1970

Giggenbach,

1984, GCA

Potassic or phyllic

Sodic-calcic

(propylitic)


3/20

Dilles et al., 2000

Ann Mason MacArthur

porphyry Cu-Mo porphyry Cu

~3 km

~3 km

Seedorff et al., 2005

Adv argillic

Seedorffet al., 2005

potassic

sericitic

potassic

sericitic

argillic

argillicT

emperature

Low

H

igh

adv. arg.

Time >

Depthkm2

4

2

4


4/20

80% 20%

Redmond etal., 2004

Cathodo-

luminscence


5/20

Grade: Cu equiv

Vein density ~40%

Vein density ~5%

Modifiedfrom LCMC,1994

-100 m elev. plan

Far Southeast porphyry, Philippines:

Cu equiv. grade and quartz vein density

Changet al.,

2011

Seedorff et al., 2005, fromHemley and Montoyo, 1964, etc.

White mica KAl3Si3O10(OH)2

PyrophylliteAl2Si4O10(OH)2

Andalusite

Al2SiO5

Dickite / kaoliniteAl2Si2O5(OH)4

(Na,Ca)1/3(Al,Mg)2(Si4O10)(OH)2!nH2O


6/20

Mineral stabilities vsfluid compositions

150

Watanabe and Hedenquist, 2001,

after Hemley et al., 1980

El Salvador, Chile: Watanabe and

Hedenquist, 2001, after Hemley et al., 1969

pyrophyllite

muscovite


7/20

Watanabe and

Hedenquist, 2001


8/20

Watanabe andHedenquist, 2001

El Salvador, Chile: Watanabe and Hedenquist, 2001

pyrophyllite alunite lithocap (late)

El Salvador, looking ~SE



9/20

Pebble

dikes

Muscoviteoverprint

(andal)trans

ition

pyroph

Watanabe and Hedenquist, 2001

Fluids from alteration at present-day level of exposure

Deep biotitedickite


2M1 musc

late Q-A

early qtz-alun

lithocap??

retrograde

pyroph

Damiana exotic

paleosurface?

encapsulated

potassic, sulfides

Lithocap with metals present??

Erosion at El Salvador


10/20

Magma mine, Arizona:1875~1990s; 2nd Ag, cc

cc-en-bn vn,

ser (dk-zy)hm-py-cp-bn

(gn-spl) mantos


11/20

E

H


12/20

1998 resource:

455 Mt at 1.2%

Cu, 0.02% Mo;

1250-1550 m

below surface,

1050 x 365 x305 m

http://riotinto.msgfocus.com/q/1cRLO25OxfDl/wv


13/20

Sericite halos to py-

qtz veins; ccp, bn,cv, cc, en, tn, spl

Chuquicamata, Chile

Rusk et al. (2008)

potassic centers

3 km

3 km

Seedorff et al., 2008

1 km Main Stage

QSP

pyrophkaol-dick

ser-

kaol

ser-

kaol

R. Sales, C. Meyer, J. Proffett, compiled by M. Einaudi

Rusk et al. (2008)

m

pre-Main Stage

(potassic)

pre-Main

Stage

(potassic)

ZnCu


14/20

Sulfide zoning

in porphyries:Greys=potassic

Lined=sericiticoverprint

Marco

Einaudi,2002,

unpub.


15/20

Bingham

Chuquicamata

Potrerillos

El Salvador

Gibraltar

Sungun

Ann Mason

Silver Bell

Sierrita-Esperanza

Butte

py-en,py-bn

py-hm-(cp)

Early, higher temp Late, lower temp

bn + cp, cp + pyss

dominant assemblageore

no pyrite pyrite

(bn-cp) dg-bn-cp

bn-cp

(dg-bn)-cp

(bn)-cpcp-py

py-cp-(tn)

mt-cp

cp-py

py-cp-bn,py-bn

py, cv, dg,en, cp

py-cp-tn

py-cp

bn-cp

(mt)-bn-cp

mt-bn-cpmt-cp-py

bn-cp

(mt-bn-cp)

py, tn, en

cp-py

dg-bn-(cp)

(bn)-cpcp-py

cp-py

cp bn-cpbn-cp,

cp-py (SC)

cp cp-py py

cp-py cp-py (C) py-cp

mt-cp-py(EDM)

mt-cp-py (SC)py-cp (S)

py, cv, dg,bn, cp, en

Early to intermediate (potassic to phyllic), high to lowT, progressively higher sulfd state in porphyry; --

metals introduced early or intermediate

Einaudi, Hedenquist,

Inan, 2003

alunite host

phyllic

potassic

illite

Einaudi et al., 2003, modifiedby Seedorff et al., 2005


16/20

Marte Au-rich porphyry,

Maricunga, Chile

Sillitoe, 1994Sillitoe, 1990

?

Singer et al., 2008J. Muntean unpub.

epithermal

Au

?


17/20

Muntean andEinaudi, 2000

1 km

Maricunga

(Refugio):

Geology

Muntean and

Einaudi, 2000Maricunga (Refugio): Verde West

Qtz diorite

porphyry


Maricunga:Pancho

Maricunga porphyry Au:

banded silica gel +mt, recrystallized

low-grade to barren



18/20

Highstrain

rate

3

2

1

0

40

Early BarrenQ uartz-Alunite Ledges

MeteoricWater

MagmaticVapor

?

MagmaticBrine

SupercriticalMagmaticFluid

BandedQuartzVeinlets

Magma

D Veins

Ore-BearingQuartz-Alunite

Ledges

Sector Collapse?

Faulting

Early Mineral ization Late Mineral ization

Approximate Time Range (m.y.)

? ? ??

1

Evolution of porphyry systems

Sillitoe, 2010 Varying depths and

intervals between base of

lithocap and top of

porphyry

Only some (few)lithocaps are mineralized

IF rapid syn-hydrothermaluplift...

lithocap collapse; HS ore, if present,

overprints porphyry

Petelovo


19/20

Wafi, Papua New GuineaTelescoped porphyry Cu-Au

Sillitoe, 1999

M. Herve, 2010

Pampa Escondida

M. Herve, 2010

37.5 Ma 37.7 Ma

36.1 Ma

Pampa Escondida

Lepanto,

FSE

Victoria

Cerro Casale

Co. Catedral

(barren)

El Salvador

Preservation of lithocap, or erosion to transitional levels


20/20

Porphyry systems

Sillitoe, 2010Economic Geology

Hedenquist et al., 1998; Chang et al., 2011

500 m

Residual (vuggy) qtz

Qtz-alun (py), dick-kaol

Porphyry systems: asymmetric (shallow) alteration

Porphyry systems: steep tilting

Sillitoe, 2010Economic Geology

Porphyry systems: deeply eroded

porphyry transitions anti ago

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