Lithocaps and high-sulfidation epithermal deposits · Lithocaps and high-sulfidation epithermal...
Transcript of Lithocaps and high-sulfidation epithermal deposits · Lithocaps and high-sulfidation epithermal...
Lithocaps and high-sulfidation epithermal deposits
Sociedad Geológica de Chile: : July 2011�
III
I
II
H2S + 2 O2 = H2SO4
H2O, NaCl, SO2, HCl, CO2, H2S, ...
H2SO4, HCl
CO2, H2S
4 SO2 + 4 H2O => 3 H2SO4 + H2S
pH >2
pH <1
Steam-heated blanket
Lithocap formed by hypogene condensate
Formation of advanced argillic alteration: hypogene & steam heated
HCl, SO2, CO2, H2S hypogene alteration
CO2, H2S steam-heated
alteration
HS IS LS HS IS LS LS(a)
Ya
RMt
Hedenquist et al., 1996, 2000
Vi To
Wa
Sl
LS, shallow (<300-400 m) <220-230 C
IS, deeper (~300-800 m) >220-230 C)
musc
Lithocaps and high sulf’n: Cu-Au-Ag
Initial leaching: vuggy qtz, qtz-alun lithocap w/ crs py, <50 ppb Au
Einaudi, Hedenquist and Inan, 2003
Summitville, Colorado
Steven and Ratté, 1960
pH ~ 4-6 2-4 <2 Summitville, Colorado
Steven & Ratté, 1960
pH ~ >6 4 - 6 2 - 4 <2
10 - 100s m
>10 g/t 500 m
Residual quartz, vuggy: Summitville Quartz-alunite, Summitville
Hypogene alunite, El Tambo Residual quartz, vuggy: Pierina
Arribas et al., 2000
Residual quartz, vuggy : Tucari
High-temperature hypogene vapors, !850 C with HCl, SO2
vadose zone: steam-heated blanket
Arribas et al. (2005) Arribas et al. (2005)
Arribas et al. (2005) Arribas et al. (2005)
Supergene alunite, Rodalquilar
Steam-heated advanced argillic blanket, La Coipa
Supergene alunite, Riaza Supergene alunite, Rodalquilar
Massive supergene alunite, Rodalquilar; post-mineral weathering oxidation
Arribas et al., 2000
Supergene oxidation critical to economics!
Rodalquilar, Spain: looking ~east
Rodalquilar, Spain
Arribas et al., 1995
Drilling beneath supergene alunite blanket; a mistake here....
Sonomi volcano
1 km
Nansatsu district, S Kyushu, looking east: Iwato HS deposit, Maruyama pit Inset: qtz-alun halo, sharp ctc with vuggy qtz, to r.)
Urashima et al., 1981
Tuff breccia Nansatsu Group
Iwato, Arabira rebody: Structural control to alteration and ore (in feeders)
30 m
MMAJ, 1986 250 m
NB: 27 drill holes on pseudo-section outside mine
http://www.iamgold.com/presentations2006.asp
Exploration and discovery histories: Use of models 1991
10 holes, 1869 m, av. 185 m
82 holes, 7656 m, av. 93 m (inclined)
IMG-122 (#40); 71 holes, 23,242 m, av. 330 m
2 km
Diatreme breccia w/ porphyry Cu fragments
Strong lithologic control to residual quartz llithocap: tuffs
“Stacked” lithocaps! “Stacked” lithocaps, upper barren...!
http://www.iamgold.com/presentations2006.asp Longitudinal section, N-S
Pierina, Peru
Volkert et al., 1998
Calipuy volcanic units
Yanacocha
oblique aerial to NE
Cajamarca District
Tantahuatay
Perol-Cocanes
Kupfertal
Cerro Yanacocha
Tertiary volcanic rocks
Paleozoic-Mesozoic sedimentary rocks
Cretaceous-Tertiary
intrusive rocks
Gustafson et al., 2004
40 km
Quilish; 4
La Quinua; 9
Tapado-Corimayo; 4
San Jose; 4 Kupfertal porphyry:
KUP-3
Carachugo-Chaquicocha; 6
Cerro Negro; 1
Leach pad
Cerro Yanacocha; 25 Norte, Oeste, Sur, Encajon
(Verde - sulfide)
Maqui Maqui; 3 Antonio
Carachugo-Chaquicocha; 6
Encajon
Sur Oeste
Norte
Giuliana
5 km
Yanacocha cluster
Longo and Teal, 2005
Perol, Cocañez: 8 km
5 km
Kupfertal
From Longo, 2005; Perol and Coca
11.5 – 13.5 Ma (Cerro Negro, Quilish)
10.7 – 11.1 Ma (Corimayo-Carachugo-Tapado)
10 – 10.5 Ma (San Jose)
8.2 – 9.2 Ma (Yanacocha Complex)
15.8-16.1 Ma (Perol porph, Cocañez litho)
10.7 Ma (Kupfertal porph)
From Longo, 2005, et al. 2010; Perol and Cocañez dates from Gustafson et al., 2004
Late dacite
Alunites
Bell et al., 2005 Longo and Teal, 2005 Longo et al., 2010
Longo et al., 2010
(7 Moz) (20 Moz) (25 Moz)
Longo, 2005; et al., 2010
Cerro Negro Quilish
San Jose Tapado
Corimayo Carachugo
Maqui Maqui
Yanacocha Complex
Km3
Moz
2 km
Hydrothermal breccia body Lithologic horizon (70% of ore in welded pyroclastics)
Margin of dome intrusion
220-ton haul truck
pH ~ >6 4 - 6 2 - 4 <2
Dome moat, laminated siliceous sediments, paleosurface...
Chaquicocha Carachugo
KUPFERTAL PORPHYRY
Patchy
Wormy
Low Au-Ag-Hg-As
Bi-Ba-As-Sb
Au-Ag-As-Sb
Cu-Au-As-Ag
oxide
sulfide
Zn-Pb
Hg
CHAQUICOCHA
~100 m
1
2 2. Cooling
1. Vapor condensation
215.3m: Muscovite
205.6m: pyrophyllite, alunite
Breccia: from 181.5m Pyrophyllite, alunite,
kaolinite
185.3m: pyrophyllite, minor alunite
Porphyry-style quartz veins with phyllic alteration
Epithermal Porphyry
DDH KUP-3
210.6m: pyrophyllite,
kaolinite
Fault contact between epithermal and porphyry alteration at Kupfertal
Fault contact
Patchy texture outcrop 0 500 m
Milagros porphyry prospect, Alto Chicama, Peru
Garia, 2009
Arribas et al., Gold in 2000
Residual quartz (silicic) and advanged argillic size matters...
El Indio 8 Moz
...much of the time, cf. El Indio
Jannas et al., 1990
100 m
Jannas et al., 1990
Qtz-alunite
Pyrophyllite- kandite
White mica
NB: Mixing will not cause amorphous silica saturation and colloform gels
Erosion level?
Lepanto,
FSE
Victoria
Perol
Co. Cocañez (barren)
Relation of porphyry, lithocap, HS ore, and marginal IS ore
Alto Chicama, Peru 10.5 Moz resource, 2003 Lagunas Norte, 1.24 g/t Au, 14 Moz
Chimu qtzites Calipuy volcanics