How metalliferous brines line Mexican epithermal veins with silver

Wilkinson, Jamie J.; Simmons, S. W.; Stoffell, Barry

doi:10.1038/srep02057

Cited by 23 publications

(10 citation statements)

References 32 publications

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“…% NaCl + CaCl 2 equiv. ), while the intermediate stages related to massive tourmalinisation show temperatures of homogenization of 200-250 • C. The system then evolves toward lower salinity fluids probably belonging to the H 2 O-NaCl-CaCl 2 (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) wt. % NaCl equiv.)…”

Section: The Qal'at Mgouna Au-ag(-bi-te) Epithermal Systemmentioning

confidence: 99%

“…Further, LIPs are commonly related to a wide variety of metal deposits [17] including world-class deposits such as magmatic sulfide ore deposits associated with mafic and ultramafic magmatism (Ni, Cu, PGE, Cr, Ti, Fe [18,19]), with carbonatite and peralkaline complexes (Nb, Ti, REE, Zr [20,21]), or with diamondiferous kimberlites [22]. Iron oxide copper gold (IOCG) deposit types [23] and epithermal deposits of mostly low and intermediate sulfidation gold-based metal types [24][25][26] may be also related to more silicic LIPs. Another magmatic event described in peri-Gondwanan terranes of, e.g., Avalonian and Cadomian types, is mostly characterised by huge volumes of pyroclastic flows and was emplaced at the end of the Neoproterozoic era [27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

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The Jbel Saghro Au(–Ag, Cu) and Ag–Hg Metallogenetic Province: Product of a Long-Lived Ediacaran Tectono-Magmatic Evolution in the Moroccan Anti-Atlas

et al. 2018

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The Jbel Saghro is interpreted as part of a long-lived silicic large igneous province. The area comprises two lithostructural complexes. The Lower Complex consists of folded metagreywackes and N070–090°E dextral shear zones, which roughly results from a NW–SE to NNW–SSE shortening direction related to a D1 transpressive tectonic stage. D1 is also combined with syntectonic plutons emplaced between ca. 615 and 575 Ma. The Upper Complex is defined by ash-flow caldera emplacements, thick and widespread ignimbrites, lavas and volcaniclastic sedimentary rocks with related intrusives that were emplaced in three main magmatic flare ups at ca. 575, 565 and 555 Ma. It lies unconformably on the Lower Complex units and was affected by a D2 trantensive tectonic stage. Between 550 and 540 Ma, the magmatic activity became slightly alkaline and of lower extent. Ore deposits show specific features, but remain controlled by the same structural setting: a NNW–SSE shortening direction related to both D1 and D2 stages. Porphyry Au(–Cu–Mo) and intrusion-related gold deposits were emplaced in an earlier stage between 580 and 565 Ma. Intermediate sulfidation epithermal deposits may have been emplaced during lull periods after the second and (or) the third flare-ups (560–550 Ma). Low sulfidation epithermal deposits were emplaced late during the felsic alkaline magmatic stage (550–520 Ma). The D2 stage, therefore, provided extensional structures that enabled fluid circulations and magmatic-hydrothermal ore forming processes.

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Section: The Qal'at Mgouna Au-ag(-bi-te) Epithermal Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Jbel Saghro Au(–Ag, Cu) and Ag–Hg Metallogenetic Province: Product of a Long-Lived Ediacaran Tectono-Magmatic Evolution in the Moroccan Anti-Atlas

et al. 2018

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“…These usually have salinities between 1 and 5 wt % NaCl equiv, but can reach intermediate compositions of 5 to 23 wt% NaCl equiv and salinities of >30 wt % NaCl equiv (Rye and Sawkins, 1974;Campbell et al, 1984;Hildreth and Hannah, 1996;Hedenquist et al, 1998;Beuchat et al, 2004;Simmons et al, 2005;Baumgartner et al, 2008;Rusk et al, 2008a;Bendezú and Fontboté, 2009). Magmatic fluid-derived base metal sulfides from such deposits are classically interpreted to have precipitated from magmatic brines diluted by meteoric waters (Landis and Rye, 1974;Kamilli and Ohmoto, 1977;John, 1989;Simmons, 1991;Deen et al, 1994;Bendezú and Fontboté, 2009) or directly from small amounts of magmatic brine (Wilkinson et al, 2013).…”

Section: P-t-salinity Evolution Of Fluidsmentioning

confidence: 99%

Zoned Base Metal Mineralization in a Porphyry System: Origin and Evolution of Mineralizing Fluids in the Morococha District, Peru

Catchpole¹,

Kouzmanov²,

Putlitz³

et al. 2014

Economic Geology

103

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Porphyry-related base metal vein and replacement mineralization (i.e., Cordilleran polymetallic mineralization) in the Morococha district, central Peru, is part of a large magmatic-hydrothermal system associated with the emplacement of several late Miocene porphyry intrusions and formation of important Cu-Mo mineralization. Zn-Pb-Ag-Cu veins overprint the giant Toromocho porphyry Cu-Mo deposit in the center of the district and display a typical concentric base metal zonation (Cu → Zn, Pb → Ag) covering an area of approximately 50km 2 .A detailed fluid inclusion study supports the hypothesis that base metal mineralization precipitated from cooled and evolved metal-rich, intermediate-density porphyry-type fluids. In early stages of Cordilleran base metal vein formation, fluid inclusions have low salinities of ~2 to 5 wt % NaCl equiv, CO2 contents of 3 to 10mol %, and homogenization temperatures (Th) of 380° to 340°C. They are similar to intermediate-density fluid inclusions trapped in a milky quartz vein predating Cordilleran polymetallic mineralization, with similar low salinities (3.0-3.8 wt % NaCl equiv) and low CO2 contents (6.5-8 mol %), but higher Th of ~420° to 410°C. During cooling of the intermediate-density fluids from 400° to 300°C, the lithostatic pressure regime changed to a hydrostatic one. The fluids underwent pressure drop as well as phase separation (i.e., unmixing) and lost most of their CO2. They acquired moderate salinities, in some cases intermediate (~up to 16 wt % NaCl) to brine compositions. However, the bulk of the magmatic fluid retained low salinity while it continued to cool under open-system conditions and precipitated tennantite-tetrahedrite, chalcopyrite, enargite, sphalerite, and galena. Upon cooling below 270°C, the fluids deposited abundant rhodochrosite and quartz, while following the boiling curve toward lower P-T conditions. These data record an evolution of mineral precipitation from deep (minimum depth of 2-1.5 km) to shallow environments (300-800 m). Oxygen, hydrogen, and carbon stable isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and were diluted by meteoric waters during the carbonate stage.Copper (5,000-18,000 µg/g), sulfur (up to 12,000 µg/g), and iron (2,100-6,000 µg/g) concentrations in the intermediate-density fluid inclusions in the milky quartz veins are approximately 5 to 10 times higher than in intermediate-density inclusions of the early Cordilleran base metal veins. The base metals Zn, Pb, and Mn have comparable concentrations between 100 and 1,000 µg/g for both types of fluid. These findings suggest that the fluids identified in Cordilleran polymetallic veins are compositionally similar to the porphyry-type fluids and could have derived from the latter after precipitation of Cu-and Fe-bearing sulfides in a deeper porphyry environment.The new data explain the commonly observed base and precious metal zonation patterns encountered in porphyry-centered districts (e.g., Bingham, Butte) and show that both porphyry and polymet...

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“…In convergent margins, subaerial geothermal systems are the modern analogues of shallow-level (2-3 km deep) intrusion-centered hydrothermal ore deposits [28]. For instance, epithermal Au-Ag deposits, formed at a depth <1.5 km and a temperature <300 • C, are regarded as the exhumed product of fossil geothermal systems, and host~6% of the world's known Au resources and~17% of the Ag resources [5,29]. In active geothermal systems, precious (Au, Ag) and base (Cu, Pb, Zn) metal mineralization occurs in the low-to-intermediate sulfidation epithermal environment, forming veins and vugs in hydrothermally altered rocks [30].…”

Section: Introductionmentioning

confidence: 99%

Silver-Rich Chalcopyrite from the Active Cerro Pabellón Geothermal System, Northern Chile

et al. 2020

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Active subaerial geothermal systems are regarded as modern analogues of low- to intermediate-sulfidation epithermal Au–Ag deposits, where minor amounts of Cu are mostly present as chalcopyrite. Although trace element data concerning sulfides are scarce in active geothermal systems at convergent settings, studies in several other environments have demonstrated that chalcopyrite is a relevant host of Ag and other trace elements. Here, we focus on the active Cerro Pabellón geothermal system in the Altiplano of northern Chile, where chalcopyrite-bearing samples were retrieved from a 561 m drill core that crosscuts the high-enthalpy geothermal reservoir at depth. A combination of EMPA and LA-ICP-MS data shows that chalcopyrite from Cerro Pabellón is silver-rich (Ag > 1000 ppm) and hosts a wide range of trace elements, most notably Se, Te, Zn, Sb, As, and Ni, which can reach 100 s of ppm. Other elements detected include Co, Pb, Cr, Ga, Ge, Sn, Cd, and Hg but are often present in low concentrations (<100 ppm), whereas Au, Bi, Tl, and In are generally below 1 ppm. Chalcopyrite shows a distinct geochemical signature with depth, with significantly higher Ag concentrations in the shallow sample (494 m) and increasing Cd and In contents towards the bottom of the studied drill core (549 m). These differences in the trace element contents of chalcopyrite are interpreted as related to temperature gradients during the waning stages of boiling at Cerro Pabellón, although further studies are still needed to assess the precise partitioning controls. Our data provide evidence that chalcopyrite may play a relevant role as a scavenger of certain metals and a monitor of fluid changes in hydrothermal systems.

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How metalliferous brines line Mexican epithermal veins with silver

Cited by 23 publications

References 32 publications

The Jbel Saghro Au(–Ag, Cu) and Ag–Hg Metallogenetic Province: Product of a Long-Lived Ediacaran Tectono-Magmatic Evolution in the Moroccan Anti-Atlas

The Jbel Saghro Au(–Ag, Cu) and Ag–Hg Metallogenetic Province: Product of a Long-Lived Ediacaran Tectono-Magmatic Evolution in the Moroccan Anti-Atlas

Zoned Base Metal Mineralization in a Porphyry System: Origin and Evolution of Mineralizing Fluids in the Morococha District, Peru

Silver-Rich Chalcopyrite from the Active Cerro Pabellón Geothermal System, Northern Chile

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