Mixing of metamorphic and surficial fluids during the uplift of the Hercynian upper crust: consequences for gold deposition

Boiron, Marie-Christine; Cathelineau, ‪Michel; Banks, David; Fourcade, Serge; Vallance, Jean

doi:10.1016/s0009-2541(02)00274-7

Cited by 106 publications

(73 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…2D). This breakdown induces precipitation of a portion of the gold, consistent with numerous observations in different types of deposits where fluid unmixing occurs (29)(30)(31)(32)(33)(34)(35)(36), with the balance constrained by the vapor phase as volatile complexes with hydrogen sulfide (4,17) or chloride (37), depending on the fluid H 2 S and HCl content, acidity, temperature, and depth of the vapor-liquid separation. For example, vapor-liquid partitioning coefficients for Au in S-rich (∼1 wt% S) acidic (pH < 5) systems at 400-500°C are above 1 (17,36), suggesting an important contribution of the vapor phase to Au transport.…”

Section: Abundance Of Gold-trisulfur Ion Complexes In Hydrothermal Flsupporting

confidence: 82%

“…The sharp drop of Au solubility between 600°C and 500°C caused by the decay of S − 3 due to decreasing solubility of pyrite (Fig. 3B) explains the observation that most gold deposits in metamorphic terrains are hosted by greenschist rock facies that correspond to temperatures ≤500°C (32)(33)(34)(35). When fluids degassing from arc magmas and carrying both reduced and oxidized sulfur, favorable for S − 3 and its Au complex, interact with reduced organic-rich sediments, massive Au precipitation occurs over a small f O2 range (e.g., from HM to PPM at 450°C, The S − 3 ion enhances Au (and, potentially, other sulfur-loving trace metals, like Mo, Pt, and metalloids) release into the fluid phase from both sulfide and silicate melts during magma evolution in arc settings, and from pyrite-bearing sedimentary and volcanic rocks upon their prograde metamorphism.…”

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 92%

“…S10), typical of arc magmas (2,3,29,31). In iron-rich metamorphic environments typical of orogenic gold deposits (7,8,10,(32)(33)(34)(35), the low solubility of pyrite at <500°C is the major limiting factor for S − 3 ; therefore, in such settings, S − 3 is capable of concentrating Au only at hot stages of metamorphism, between 500°C and 700°C, where S − 3 concentrations are high enough to yield Au-enriched fluids within amphibolite facies (Fig. 3B).…”

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

“…S9). In the presence of large CO 2 concentrations (>10-20 wt%) common in fluids of orogenic-type gold deposits (10,(33)(34)(35), the relative abundances of AuðHSÞS − 3 versus AuðHSÞ − 2 are only slightly affected compared with an aqueous solution at the same T-P-pH-f O2 conditions, even though the absolute concentrations of both charged species are expected to be lower in the CO 2 -H 2 O solvent due to its low dielectric constant, which is unfavorable for the stability of charged species (4,6). Fluid immiscibility that is common in porphyry, epithermal, and many orogenic deposits (2, 9, 10, 29-35) is another factor influencing both S − 3 and Au behavior.…”

Section: Abundance Of Gold-trisulfur Ion Complexes In Hydrothermal Flmentioning

confidence: 99%

See 3 more Smart Citations

Sulfur radical species form gold deposits on Earth

Pokrovski

Kokh

Guillaume

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

128

View full text Add to dashboard Cite

Current models of the formation and distribution of gold deposits on Earth are based on the long-standing paradigm that hydrogen sulfide and chloride are the ligands responsible for gold mobilization and precipitation by fluids across the lithosphere. Here we challenge this view by demonstrating, using in situ X-ray absorption spectroscopy and solubility measurements, coupled with molecular dynamics and thermodynamic simulations, that sulfur radical species, such as the trisulfur ion S − 3 , form very stable and soluble complexes with Au + in aqueous solution at elevated temperatures (>250°C) and pressures (>100 bar). These species enable extraction, transport, and focused precipitation of gold by sulfur-rich fluids 10-100 times more efficiently than sulfide and chloride only. As a result, S − 3 exerts an important control on the source, concentration, and distribution of gold in its major economic deposits from magmatic, hydrothermal, and metamorphic settings. The growth and decay of S − 3 during the fluid generation and evolution is one of the key factors that determine the fate of gold in the lithosphere.gold | sulfur | ore deposit | hydrothermal fluid | trisulfur ion

show abstract

Section: Abundance Of Gold-trisulfur Ion Complexes In Hydrothermal Flsupporting

confidence: 82%

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 92%

Section: Discussion and Geological And Metallogenic Applicationsmentioning

confidence: 99%

Section: Abundance Of Gold-trisulfur Ion Complexes In Hydrothermal Flmentioning

confidence: 99%

See 2 more Smart Citations

Sulfur radical species form gold deposits on Earth

Pokrovski

Kokh

Guillaume

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

128

View full text Add to dashboard Cite

show abstract

“…4,5,8,31,32]. The spatial association of brittle and ductile structures (fractures, foliations, lineations) genetically suggests similar stress conditions of formation [33]. …”

Section: Structural Controlmentioning

confidence: 99%

Quartz Veins Characteristics and Au Mineralization Within the Batouri Au District, East Cameroon

Yannah¹

2015

View full text Add to dashboard Cite

Abstract:The Batouri south Au district of East Cameroon is hosted by biotite-amphibole meta-granites that belong to the Pan-African group of Pre-to Syn D 1 and D 2 Neoproterozoic granitoids. Hydrothermal activity and Au mineralization in this area is greatly enhanced by the presence of fractures, foliations, faults (sinistral) and vein splays hosted within a foliated metagranite basement. Thirteen samples of 1.00 kg each of quartz vein were crushed and panned for Au-grain recovery. Fire Assay geochemistry was used to analyze eighteen samples for Au. Field results identified foliated and non-foliated GQV/BQV quartz vein varieties. The mineralization style in the area is mainly by fracture filled. Disseminated Au is common in the weathered wall rock envelop associated with mineralized veinlets. Au-grade from fire assay geochemistry varies from ~0.056 g/t to 2.844 g/t similar to 3-4 g/t Au-grade from field analysis associated with the GQV veinlets and weathered wall rock. The highest Augrade was obtained from the foliated variety of GQV (QV 2 ). Recovered Au-grains varied in shape and sizes (102-392 µm).

show abstract

Fluid circulation in the South Tibetan Detachment System: Evidence from fluid inclusions and oxygen isotope data of quartz veins in the Ramba Dome, North Himalayan Gneiss Domes

Zhang

Cheng

et al. 2021

Geological Journal

View full text Add to dashboard Cite

Detachment faults are sites of intensive fluid-rock interactions. Here, we report fluid inclusion and oxygen isotope data for quartz veins in the Ramba Dome in the North Himalayan Gneiss Domes, with an aim to constrain the origin and circulation of crustal fluids associated with the South Tibetan Detachment System (STDS). Microthermometric data for fluid inclusions in quartz indicate that the fluids were aqueous and CO 2 À H 2 O ± CH 4 ± N 2 -bearing with low to moderate salinities (0.60-11.80 wt% eq. NaCl). The entrapment conditions are 295-410 C and 98-135 Mpa, indicating a forming-depth of 8-10 km. Oxygen isotopic compositions (δ 18 O) of quartz measured in situ by secondary ion mass spectrometry and bulk by the BrF 5 method show limited variations in individual quartz veins, but δ 18 O quartz values vary from 12.07 to 18.16‰ (V-SMOW) among veins. The corresponding δ 18 O fluid values range from 7.71 to 13.80‰, based on equilibrium temperatures obtained from fluid inclusions. From the footwall to the detachment zone, δ 18 O fluid values exhibit a broadly decreasing trend and indicate that the STDS dominated the fluid flux pathway in the crust, with more contributions of meteoric water in the detachment zone. We further quantified the contribution of meteoric fluids to 8-27% using a binary end-member mixing model. These data imply that the fluids were predominantly metamorphic/ magmatic in origin, and were mixed with infiltrating, isotopically light, meteoric water during extensional detachment shearing of the STDS. The meteoric water can infiltrate from the surface to 8-10 km depth. K E Y W O R D S fluid circulation, fluid inclusions, gneiss dome, mixing processes, oxygen isotopes, quartz veins, South Tibetan Detachment System 1 | INTRODUCTION Stable isotopes in fluids and minerals have been widely utilized to fingerprint the origins and fluxes of fluids over a wide range of timescales and geological settings, such as in basins, thrust fault zones,

show abstract

Mixing of metamorphic and surficial fluids during the uplift of the Hercynian upper crust: consequences for gold deposition

Cited by 106 publications

References 39 publications

Sulfur radical species form gold deposits on Earth

Sulfur radical species form gold deposits on Earth

Quartz Veins Characteristics and Au Mineralization Within the Batouri Au District, East Cameroon

Fluid circulation in the South Tibetan Detachment System: Evidence from fluid inclusions and oxygen isotope data of quartz veins in the Ramba Dome, North Himalayan Gneiss Domes

Contact Info

Product

Resources

About