Upload
oguzgeo
View
226
Download
0
Embed Size (px)
Citation preview
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
1/46
Aspects of Lachlan Orogen
Magmatic Arc Cu-Au-Ag Exploration
with lessons from the Pacific rim
Greg Corbett
www.corbettgeology.com
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
2/46
Terry LeachSymposium
2008
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
3/46
Model for Pacific rim magmatic arc Cu-Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
4/46
Mines & Wines Lachlan Orogen
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
5/46
Porphyry Cu-Au with time
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
6/46
Magnetite destruction
by phyllic (sericite)alteration overprint
(of potassic alteration)
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
7/46
Overprinting alteration and magnetics
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
8/46
Overprinting
intrusions and veins
Ridgeway, Straya
Rio Grande, Argentina
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
9/46
Overprinting intrusions
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
10/46
Fluid evolution and levels in
Porphyry Cu-Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
11/46
Wall rock porphyry
Gaby, Ecuador
Cadia Australia
Maricunga Belt, Chile
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
12/46
Porphyry - wall rock porphyry
Exploration implications Highest value targets
Complex overprinting relationships increase metal grade
Position in the anatomy is critical (late barren intrusions)
Structural control to sheeted veins important
Oyu TolgoiMaricunga
b b l
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
13/46
Carbonate-base metal Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
14/46
Carbonate-base metal Au Leach and Corbett, 1993, 1994, 1995; Corbett and Leach, 1998
Porgera
Kelian
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
15/46
Polymetallic Ag-Au
carbonate base metal Au
sphalerite zonation
Kelian, Indonesia
Bowdens,
Australia
Kumrock,
Kamchatka,
E. Russia
San Martin
Peru
C b t b t l A
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
16/46
Carbonate base metal Au
carbonate types
Upper Ridges, Wau, PNG
Mt Kare, PNG
C l
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
17/46
Cowal-
Carbonate -base metal Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
18/46
Cowal pull-apart basin fractures
Ch i i
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
19/46
Changes in convergence as a trigger
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
20/46
Carbonate-base metal Au
Exploration implications Most prolific Au producers in the SW Pacific rim
Au with zoned Zn>Pb and carbonate
Irregular Au distribution & variable metallurgy
Local overprinting bonanza Au
Structural control to bleed fluids from magmatic source
Porgera
Polymetallic Ag Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
21/46
Polymetallic Ag-Au
A d P l t lli A A Caylloma Peru
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
22/46
Andean Polymetallic Au-Ag Caylloma, Peru
Arcata, Peru
1000 oz/t Ag
Polymetallic Ag Au Mexico
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
23/46
Polymetallic Ag-Au Mexico
FresnilloPalmarejo
P l lli A Z Pb
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
24/46
Polymetallic Ag-Zn-Pb
Corani, Peru San Cristobal, Bolivia
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
25/46
Zonation in polymetallic Ag-Au
Tops white (Zn-rich) sphalerite, siderite,
elevated precious metal grades, Ag>Au
Bottoms black (Zn-poor) sphalerite,chalcopyrite
Huevos Verde
Caylloma
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
26/46
Mungana
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
27/46
Polymetallic Ag-Au (Pb-Zn-Cu)
Overlooked by the majors or many years but company
makers for juniors
Ag>Au Spatially zoned with bonanzas in lower temperatures
Multiple control to ore shoot development
Corani, Peru Palmarejo, Mexico
High sulphidation epithermal Au + Cu+ Ag
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
28/46
High sulphidation epithermal Au + Cu+ Ag
High sulphidation Cu-Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
29/46
High sulphidation Cu Au
A d hi h l hid ti A A
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
30/46
Andean high sulphidation Au-Ag
La Coipa, Chile Veladero, Argentina
Yanacocha, PeruPascua-Lama, Chile-Argentina
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
31/46
High vs Low Sulphidation
CENTRAL
HOT ACID
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
32/46
High sulphidation
Zoned acid alteration
HOT ACID
OUTER
LESS ACID
Alunite
Pyrophyllite-diaspore
Dickite-kaolinite
Alt ti ti
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
33/46
Alteration cross section
- Nena, PNG
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
34/46
Two phase fluid flow model
Hi h l hid ti i l
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
35/46
High sulphidation mineralogy
El Indio, Chile
Nena, Papua New Guinea
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
36/46
Permeability
Breccia
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
37/46
Breccia
Lepanto, Phillipines
Veladero, Argentina
Yanacocha, Peru
Pascua, Chile
Lith l i l C t l
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
38/46
Lithological Control
Pierina, Peru
VughyVughy silica altered ignimbritesilica altered ignimbrite
LongLong Section.VolkertSection.Volkert et al 1998et al 1998
Structural controlStructural control -- El Indio ChileEl Indio Chile
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
39/46
Structural controlStructural control - El Indio, ChileEl Indio, Chile
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
40/46
Mt Carlton
Polybasite
9Ag2S.Sb2S3
El Indio
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
41/46
El Indio
Chile
HighSulphidation
Low
Sulphidation
Wafi, Papua New Guinea
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
42/46
Transition to low sulphidation
from Leach, 1999
High sulphidation
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
43/46
High sulphidation
Exploration Implications Zoned alteration & permeability controls
Often poor metallurgy & low Au grade
Better Au grade & metallurgy with temporal & spatial
transition to lower sulphidation
Caution with barren advanced argillic alteration
Model for Pacific rim magmatic arc Au
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
44/46
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
45/46
Good prospecting!!
7/29/2019 Greg Corbett - Lachlan Orogen Magmatic Arc Au-Cu-Ag
46/46