Porphyry and High-Sulfidation Epithermal Mineralization in the Nevados Del Famatina Mining District, Argentina

1998 ◽  
pp. 91-117
2020 ◽  
Vol 115 (1) ◽  
pp. 129-152
Author(s):  
Fredrik Sahlström ◽  
Zhaoshan Chang ◽  
Antonio Arribas ◽  
Paul Dirks ◽  
Craig A. Johnson ◽  
...  

Abstract The Mt. Carlton Au-Ag-Cu deposit, northern Bowen basin, northeastern Australia, is an uncommon example of a sublacustrine hydrothermal system containing economic high-sulfidation epithermal mineralization. The deposit formed in the early Permian and comprises vein- and hydrothermal breccia-hosted Au-Cu mineralization within a massive rhyodacite porphyry (V2 open pit) and stratabound Ag-barite mineralization within volcano-lacustrine sedimentary rocks (A39 open pit). These orebodies are all associated with extensive advanced argillic alteration of the volcanic host rocks. Stable isotope data for disseminated alunite (δ34S = 6.3–29.2‰; δ18OSO4 = –0.1 to 9.8‰; δ18OOH = –15.3 to –3.4‰; δD = –102 to –79‰) and pyrite (δ34S = –8.8 to –2.7‰), and void-filling anhydrite (δ34S = 17.2–19.2‰; δ18OSO4 = 1.8–5.7‰), suggest that early advanced argillic alteration formed within a magmatic-hydrothermal system. The ascending magmatic vapor (δ34SΣS ≈ –1.3‰) was absorbed by meteoric water (~50–60% meteoric component), producing an acidic (pH ≈ 1) condensate that formed a silicic → quartz-alunite → quartz-dickite-kaolinite zoned alteration halo with increasing distance from feeder structures. The oxygen and hydrogen isotope compositions of alunite-forming fluids at Mt. Carlton are lighter than those documented at similar deposits elsewhere, probably due to the high paleolatitude (~S60°) of northeastern Australia in the early Permian. Veins of coarse-grained, banded plumose alunite (δ34S = 0.4– 7.0‰; δ18OSO4 = 2.3–6.0‰; δ18OOH = –10.3 to –2.9‰; δD = –106 to –93‰) formed within feeder structures during the final stages of advanced argillic alteration. Epithermal mineralization was deposited subsequently, initially as fracture- and fissure-filling, Au-Cu–rich assemblages within feeder structures at depth. As the mineralizing fluids discharged into lakes, they produced syngenetic Ag-barite ore. Isotope data for ore-related sulfides and sulfosalts (δ34S = –15.0 to –3.0‰) and barite (δ34S = 22.3–23.8‰; δ18OSO4 = –0.2 to 1.3‰), and microthermometric data for primary fluid inclusions in barite (Th = 116°– 233°C; 0.0–1.7 wt % NaCl), are consistent with metal deposition at temperatures of ~200 ± 40°C (for Au-Cu mineralization in V2 pit) and ~150 ± 30°C (Ag mineralization in A39 pit) from a low-salinity, sulfur- and metal-rich magmatic-hydrothermal liquid that mixed with vapor-heated meteoric water. The mineralizing fluids initially had a high-sulfidation state, producing enargite-dominated ore with associated silicification of the early-altered wall rock. With time, the fluids evolved to an intermediate-sulfidation state, depositing sphalerite- and tennantite-dominated ore mineral assemblages. Void-filling massive dickite (δ18O = –1.1 to 2.1‰; δD = –121 to –103‰) with pyrite was deposited from an increasingly diluted magmatic-hydrothermal liquid (≥70% meteoric component) exsolved from a progressively degassed magma. Gypsum (δ34S = 11.4–19.2‰; δ18OSO4 = 0.5–3.4‰) occurs in veins within postmineralization faults and fracture networks, likely derived from early anhydrite that was dissolved by circulating meteoric water during extensional deformation. This process may explain the apparent scarcity of hypogene anhydrite in lithocaps elsewhere. While the Mt. Carlton system is similar to those that form subaerial high-sulfidation epithermal deposits, it also shares several key characteristics with magmatic-hydrothermal systems that form base and precious metal mineralization in shallow-submarine volcanic arc and back-arc settings. The lacustrine paleosurface features documented at Mt. Carlton may be useful as exploration indicators for concealed epithermal mineralization in similar extensional terranes elsewhere.


2016 ◽  
Vol 438 ◽  
pp. 36-57 ◽  
Author(s):  
Vesselin M. Dekov ◽  
Olivier Rouxel ◽  
Kalin Kouzmanov ◽  
Luca Bindi ◽  
Dan Asael ◽  
...  

2021 ◽  
Vol 73 (1) ◽  
pp. A101220
Author(s):  
José Perelló ◽  
Robert A. Creaser ◽  
Alfredo García

Dear Editor, we thank Corral (2020) for his anticipated interest in our paper on the timing of the porphyry-related high-sulfidation epithermal mineralization at Cerro Quema in the Azuero peninsula of southwestern Panama. Our study, based on three Re-Os ages for molybdenite intimately associated with Cu-bearing sulfide minerals from the hypogene roots of the La Pava center (Figure 1), shows that the main event of high-sulfidation Cu mineralization took place during the earliest Maastrichtian at ~71 Ma. The reported ages, together with the geologic relationships described in our paper (Perelló et al., 2020), plus a series of regional geologic, structural, petrochemical, and geotectonic considerations, not only precisely date the porphyry-related nature of the Cerro Quema high-sulfidation mineralization, but are also significant in that they confirm the rapid evolution of the earliest stages of the Central American Arc – from subduction initiation at 75-73 Ma to arc stability and maturation at 71 Ma (e.g., Buchs et al., 2011a and references therein) – and place the mineralization in a regional geodynamic setting. Irrespective of the regional geologic arguments reiterated by Corral (2020) in support of his previous genetic interpretation (e.g., Corral et al., 2016) and to invalidate our conclusions, Corral´s real concern is the reliability of our molybdenite ages, which are much older than his preferred age of mineralization for Cerro Quema. We believe that many of the points raised by Corral (2020), including the regional and local geologic backgrounds of the deposit and the dated samples, were properly addressed in Perelló et al. (2020), and that it would be redundant to repeat them here. Additional petrochemical evidence in support can be found in Whattam and Stern (2015, 2020) and Whatam (2018).


Author(s):  
Yu Yu Myaing ◽  
Arifudin Idrus ◽  
Anastasia Dewi Titisari

The Tumpangpitu high sulfidation (HS) epithermal gold deposit is located in the south coast of East Java, Banyuwangi District, East Java Province, Indonesia. This area lies within the central portion of the Cenozoic Sunda‐Banda magmatic arc which trends southeast from northern Sumatra to west Java then eastward through east Java, Bali, Lombok, Sumbawa and terminating at Banda sea. The geology of the Tumpangpitu is predominantly occupied by Late Oligocene to Middle Miocene low-K calc-alkaline to alkaline andesitic volcanic rocks and interbedded with volcaniclastic rock sequences, which are associated with low-K intermediate intrusions. The mineralization style at the Tumpangpitu area is composed of a high‐sulfidation (HS) epithermal gold-copper system which is typically associated with concealed gold-rich porphyry copper system. The HS epithermal mineralization is hosted by volcanic and volcaniclastic rocks in this research area. The mineralization domains are divided into Zone A, Zone B and Zone C which are situated along NW-SE-trending silica ledges zones. The HS epithermal mineralization is texturally occurs as vuggy replacements mineralization as well as stockworks, disseminated forms, fractures and veins. Fluid inclusion study was conducted for 6 quartz vein samples which petrographically entrapped fluid inclusions. Homogenization temperature (Th) and melting temperature (Tm) can microthermometrically be determined by fluid inclusion analysis. The average homogenization temperature (Th) of the fluid inclusions gives 180˚C to 342˚C and melting temperature are from -0.1 ˚C to -1.4˚C. Tm corresponds to the salinities ranging from 0.1 to 4.5 wt% NaCl equivalent. The paleodepth of ore formation can be estimated from the salinity of fluid. Since the deposit was not formed at boiling condition, the minimum paleodepth of ore (quartz) samples taken from both shallow level (53.35 m) and deep level (135.15 m) is determined at 650m and 1,220 m, respectively. The microthermometric data point out that the Tumpangpitu deposit formed at moderate temperature and low salinity by magmatic fluid mixing and dilution by meteoric water during the hydrothermal fluid evolution. On the basis of the fluid inclusion microthermometric data and its other key characteristics, the Tumpangpitu gold mineralization shares some similarities compared to other typical HS-epithermal gold deposits worlwide although it also shares few differences.


2005 ◽  
Vol 100 (2) ◽  
pp. 253-272
Author(s):  
S. E. Kesler ◽  
I. H. Campbell ◽  
C. N. Smith ◽  
C. M. Hall ◽  
C. M. Allen

2017 ◽  
Vol 50 (4) ◽  
pp. 1969
Author(s):  
K. Papavasiliou ◽  
P. Voudouris ◽  
C. Kanellopoulos ◽  
D. Alfieris ◽  
S. Xydous

The Triades-Galana Pb-Zn-Ag-Au mineralization is a shallow-submarine epithermal mineralization located along NE-trending faults, NW Milos Island, Greece. It is hosted in 2.5–1.4 Ma pyroclastic rocks and is genetically related to andesitic/dacitic lava domes. Mineralization occurs as breccias, quartz-barite galena veins and stockworks within sericite-adularia or kaolinitic altered rocks. The mineralization is enriched in Mo, W and base- and precious metals (e.g. Pb, Zn, Ag) similarly to the neighbouring mineralization at Kondaros-Katsimouti and Vani, indicating common source of metals from a deep buried granitoid feeding western Milos with metals and volatiles. Paragenetic relations suggest early deposition of pyrite, followed by famatinite, polybasite and Ag-rich tetrahedrite, and then by enargite, suggesting fluctuating sulfidation states during ore formation. The evolution from Sb- towards As-rich enrichment indicate a renewed magmatic pulse (probably in the form of magmatic gases) in the hydrothermal system. Silver is present in the structure of sulfosalts (up to 66.2 wt.% in polybasite-pearceite, 15.1 wt.% in tetrahedrite and 60 wt. % in pyrargyrite). Boiling processes (as evidenced by the presence of adularia accompanying intermediate-sulfidation ore) and mixing with seawater (presence of hypogene lead chlorides) and contemporaneous uplift, contributed to ore formation.


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