Mapping Advanced Argillic Alteration at Cuprite, Nevada, Using Imaging Spectroscopy

2014 ◽  
Vol 109 (5) ◽  
pp. 1179-1221 ◽  
Author(s):  
G. A. Swayze ◽  
R. N. Clark ◽  
A. F. H. Goetz ◽  
K. E. Livo ◽  
G. N. Breit ◽  
...  
Keyword(s):  
Imaging Spectroscopy ◽  
Argillic Alteration ◽  
Advanced Argillic Alteration

Age and origin of advanced argillic alteration at the Bor Cu-Au deposit, Serbia

2005 ◽  
pp. 541-544
Author(s):  
C. Lerouge ◽  
L. Bailly ◽  
E. Béchu ◽  
C. Fléhoc ◽  
A. Genna ◽  
...  
Keyword(s):  
Argillic Alteration ◽  
Advanced Argillic Alteration

Synchronous advanced argillic alteration and deformation in a shear zone-hosted magmatic hydrothermal Au-Ag deposit at the Temora (Gidginburg) Mine, New South Wales, Australia

1995 ◽  
Vol 90 (6) ◽  
pp. 1570-1603 ◽  
Author(s):  
Andrew H. Allibone ◽  
Geoffrey R. Cordery ◽  
Gregg W. Morrison ◽  
Subhash Jaireth ◽  
Jeffrey W. Lindhorst
Keyword(s):  
Shear Zone ◽  
New South ◽  
New South Wales ◽  
South Wales ◽  
Argillic Alteration ◽  
Advanced Argillic Alteration

The Onto Cu-Au Discovery, Eastern Sumbawa, Indonesia: A Large, Middle Pleistocene Lithocap-Hosted High-Sulfidation Covellite-Pyrite Porphyry Deposit

2020 ◽  
Vol 115 (7) ◽  
pp. 1385-1412
Author(s):  
David R. Burrows ◽  
Michael Rennison ◽  
David Burt ◽  
Rod Davies
Keyword(s):  
Sea Level ◽  
Shallow Depth ◽  
Middle Pleistocene ◽  
High Sulfidation ◽  
Copper Mineralization ◽  
Argillic Alteration ◽  
Zircon Crystallization ◽  
Current Resource ◽  
Advanced Argillic Alteration ◽  
Host Rocks

Abstract In 2013, a diamond drill program tested an extensive advanced argillic alteration lithocap within the Hu’u project on eastern Sumbawa Island, Indonesia. A very large and blind copper-gold deposit (Onto) was discovered, in which copper occurs largely as disseminated covellite with pyrite, and as pyrite-covellite veinlets in a tabular block measuring at least 1.5 × 1 km, with a vertical thickness of ≥1 km. Copper and gold are spatially related with a series of coalesced porphyry stocks that intrude a polymictic diatreme breccia capped by a sequence of intramaar laminated siltstones, volcaniclastic and pyroclastic rocks, and overlain by andesite flows and domes. The porphyry intrusions were emplaced at shallow depth (≤1.3 km), with A-B–type quartz veinlet stockworks developed over a vertical interval of 300 to 400 m between ~100 and 500 m below sea level (bsl), 600 to 1,000 m below the present surface, which is at 400 to 600 m above sea level. In the area drilled at Onto, the diatreme breccia, all porphyry intrusions and, to a lesser extent, the surrounding older andesite sequence have all been overprinted by intense subhorizontal advanced argillic alteration, zoned downward from illite-smectite, quartz-dickite to quartz-alunite and quartz-pyrophyllite ± diaspore alteration. The alteration package includes two particularly well-developed zones of residual quartz with vuggy texture in subhorizontal zones at shallow depth, the upper one is still porous but the lower horizon, ~100 m thick, is largely silicified and is located at or near the top of the quartz-alunite alteration. Mineralization starts below the lowermost silicic horizon with more than 90% of the current resource in quartz-pyrophyllite-alunite and quartz-alunite alteration. Mineralization is dominated by a high-sulfidation assemblage of covellite-pyrite ± native sulfur largely in open-space fillings and replacements, but also as discrete pyrite-covellite and covellite only veins down to at least 1 km. Although the greatest amount of copper occurs as paragenetically late covellite deposited during formation of the advanced argillic alteration, approximately 60% of resource at 0.3% Cu cutoff still occurs within the porphyry stocks, indicating the porphyry stocks are a fundamental control on mineralization. There is considerable remobilization and dispersion of copper and, to a lesser extent, gold into the surrounding pre-mineral breccia and the late intermineral intrusions from the two earliest porphyry phases, resulting in quite consistent copper and gold grades throughout the currently delineated mineral resource. The very high sulfidation state of the mineralization is thought to be a consequence of the metal-bearing ore fluids cooling in the advanced argillic-altered host rocks in the absence of a rock buffer. Early chalcopyrite-bornite ± pyrite mineralization with potassic ± chloritic and sericitic alteration is only preserved on the margins of the system and more rarely at depth in a few holes 600 m bsl (~1,100 m below surface) but makes up only a small proportion (~8%) of the current resource. The Onto system is exceptionally young and formed rapidly in the middle Pleistocene and is not significantly eroded. A U-Pb zircon age for the andesite that caps the volcanosedimentary host rocks provides a maximum age of 0.838 ± 0.039 Ma, with a slightly younger porphyry zircon crystallization age of 0.688 ± 0.053 Ma. Re-Os dating of molybdenite that is associated with both the quartz vein stockwork and high-sulfidation assemblage copper mineralization shows overlap between 0.44 ± 0.02 and 0.35 ± 0.0011 Ma. 40Ar/39Ar ages for alunite within the advanced argillic alteration block ranges from 0.98 ± 0.22 to 0.284 ± 0.080 Ma, and alunite closely associated with covellite spans a period from 0.537 ± 0.064 to 0.038 ± 0.018 Ma.

Acid sulphate alteration in a magmatic hydrothermal environment, Barton Peninsula, King George Island, Antarctica

1995 ◽  
Vol 59 (396) ◽  
pp. 429-441 ◽  
Author(s):  
Debbie C. Armstrong
Keyword(s):  
Alteration Zone ◽  
Near Surface ◽  
Acid Sulphate ◽  
Argillic Alteration ◽  
Barton Peninsula ◽  
Acidic Conditions ◽  
Advanced Argillic Alteration ◽  
Hydrothermal Environment ◽  
First Time ◽  
Textural Evidence

AbstractVolcanic-hosted advanced argillic alteration on Barton Peninsula comprises an assemblage of chalcedonic silica, alunite family minerals, pyrophyllite, pyrite, native sulphur, zunyite and rutile, characteristic of an acid sulphate-type epithermal system. The minerals minamiite, (Na0.36Ca0.27K0.1□0.27)Al3(SO4)2(OH)6, and zunyite, Al13Si5O20(OH,F)18Cl, are reported at this locality, and in Antarctica, for the first time. The WNW-striking, 1 km-long zone of alteration is hosted by early Tertiary andesitic rocks and contained in a 1.5 km-wide depression, rimmed by an arcuate ridge, probably representing a volcanic crater or small caldera structure.Stability relations of minerals in the advanced argillic alteration zone indicate alteration took place under acidic conditions in the near-surface environment. Mineralogical and textural evidence also suggest alteration occurred in a magmatic hydrothermal system, possibly with a magmatic steam component, rather than in a supergene or steam-heated environment.

scholarly journals Geology and mineralogy of advanced argillic alteration in the Keshe area (Mt. Karkas), Central Iran

2008 ◽  
Vol 51 (1) ◽  
pp. 85-98 ◽  
Author(s):  
Batoul Taghipour ◽  
Mohammad Ali Mackizadeh ◽  
Mehdi Pourmoghani ◽  
Arthur Kasson ◽  
Sedighe Taghipour
Keyword(s):  
Central Iran ◽  
Area Mt ◽  
Argillic Alteration ◽  
Advanced Argillic Alteration

Successive geothermal, volcanic-hydrothermal and contact-metasomatic events in Cenozoic volcanic-arc basalts, South Shetland Islands, Antarctica

2002 ◽  
Vol 139 (2) ◽  
pp. 209-231 ◽  
Author(s):  
ROBERT C. R. WILLAN ◽  
DEBBIE C. ARMSTRONG
Keyword(s):  
Porphyry Copper ◽  
South Shetland Islands ◽  
Geothermal System ◽  
King George Island ◽  
Near Surface ◽  
Volcanic Arc ◽  
Argillic Alteration ◽  
Calcite Veins ◽  
Propylitic Alteration ◽  
Advanced Argillic Alteration

Hydrothermal alteration in volcanic arcs occurs in many settings and may involve magmatic, marine, lacustrine or groundwaters, driven by magmatic, tectonic or thermal events. King George Island, part of the South Shetland Island Cenozoic volcanic arc, contains an 80 km long zone of propylitized volcanic rocks, with numerous occurrences of quartz veining, silicic, sericitic, argillic and advanced-argillic alteration. On Barton Peninsula, a basaltic lava sequence (49–44 Ma) intruded by a small, high-level granodiorite pluton (∼42 Ma), contains these alteration types, previously interpreted as a single porphyry-copper system. In this study, we report three, possibly four, distinct fossil hydrothermal episodes. (1) Banded chalcedonic quartz, quartz-sericite and propylitic alteration occurs along ESE faults and as reworked clasts in nearby tuffs. Drusy quartz + calcite veins with silicic/sericitic, argillic and propylitic wallrocks may represent feeders to the near-surface silicification. These characteristics, and anomalous Ag + Pb + Sb + Au plus Te + Se + Zn + As, suggest a neutral-pH geothermal system that was active during volcanism. (2) The lavas and banded-quartz rocks were brecciated, veined and replaced by alunite+native sulphur+pyrite, and pyrophyllite + quartz + pyrite + zunyite + diaspore assemblages with anomalous Hg + Se + As + Bi + Au + Tl + Sb + Cu. Such advanced-argillic alteration is diagnostic of degassing of a felsic magma into shallow (<500 m) meteoric groundwaters. Rhyolite tuffs, previously not reported on King George Island, may represent leakage of this magma to the surface. (3) Subsequent burial to ∼3 km was followed by emplacement of a granodiorite pluton and formation of a silicic contact-metasomatic aureole containing muscovite, biotite, actinolite, magnetite, K-feldspar and tourmaline. Disseminated andalusite + corundum also formed in areas previously affected by the advanced-argillic alteration. Iron/copper-sulphide veinlets are locally abundant, but a porphyry-style geochemical signature is not present. Early Cretaceous Ar–Ar ages near the intrusive contact indicate flow of an excess Ar-bearing hydrothermal plume up the contact. Finally, isolated areas of propylitic alteration in the lavas nearby may be related either to quartz veins of episode 1 at depth or to (4) continued circulation of heated groundwaters around the cooling pluton.

Sign in / Sign up

Export Citation Format

Share Document