Experimental modeling of Au and Pt coupled transport by chloride hydrothermal fluids at 350–450°C and 500–1000 bar

Зотов, А. В.; Тагиров, Б. Р.; Koroleva, L. A.; Volchenkova, V. A.

doi:10.1134/s1075701517050063

Cited by 7 publications

(4 citation statements)

References 30 publications

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“…Previous experimental and theoretical studies demonstrated that Au chloride and hydrosulfide complexes are the most important species responsible for hydrothermal Au mobilization in the systems considered above, with Au–Cl complexes usually predominating at temperatures above 350 °C . The chemistry of Au in chloride systems has been experimentally studied via measurements of Au solubility at 300–600 °C and pressure up to 1800 bar (e.g., Zotov and Baranova; Zotov et al; − Archibald et al; Stefánsson and Seward; see also reviews of Barnes; Brugger et al, and references therein). Guo et al reported the solubility of Au up to 800 °C/2300 bar.…”

Section: Introductionmentioning

confidence: 99%

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Тагиров

Trigub

Filimonova

et al. 2018

ACS Earth Space Chem.

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Chloride-bearing fluids are widespread in the Earth’s interior from low-temperature subsurface conditions to deep lithosphere. The concentration of chloride salts varies from diluted aqueous solutions to concentrated brines and anhydrous (dry) chloride melts beneath volcanoes. Here we report an investigation of the state of Au in hydrothermal chloride fluids and anhydrous melts by means of in situ X-ray absorption spectroscopy combined with ab initio molecular dynamics simulations and thermodynamic modeling. The experiments included registration of Au L3-edge X-ray absorption near edge structure/extended X-ray absorption fine structure spectra of Au-bearing fluids in the temperature range from 350 to 575 °C at pressures of 150–4500 bar. Spectra of Au dissolved in dry CsCl/NaCl/KCl + K2S2O8 melt were recorded at 650 °C. It was found that Au is coordinated by two Cl atoms (R Au–Cl = 2.25–2.28 Å). The alkali metal atoms (Me) were detected in the distant coordination sphere of Au at R Au‑Me = 3.3–4.1 Å. The alkali metal cations in the vicinity of Au–Cl complex partly compensate the positive charge located on Au and, by this way, affect the Au–Cl distance. An increase of the fluid pressure causes expansion of the second coordination sphere composed of the alkali metal cations, which leads to the increase of the positive Au charge and results in slight contraction of the first coordination sphere of Au. Accordingly, the transport of Au in high-temperature chloride-bearing natural ore-forming fluids of moderate to high densities (>0.3 g·cm–3) can be explicitly described by the formation of the AuCl2 – at any salt concentration from low-salinity fluids to hydrosaline liquids and anhydrous melts. In general, this means that the hydrothermal fluid chemistry simplifies with increasing temperature.

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Section: Introductionmentioning

confidence: 99%

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Тагиров

Trigub

Filimonova

et al. 2018

ACS Earth Space Chem.

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“…Zotov et al . (2017) showed experimentally that Au/Pt in high-temperature chloride fluid in equilibrium with native Au, native Pt and Pt sulfide increases up to one order of magnitude with increasing temperature from 550 to 700°C. A decrease in pressure and an increase in sulfur fugacity towards pyrite predominance over pyrrhotite also lead to enrichment of the fluid in Au relative to Pt.…”

Section: Discussionmentioning

confidence: 99%

“…Zotov et al . (2017) suggested that these coupled tendencies are related to a drop in the fluid density and exsolution of low density supercritical fluid at ~550°C that may be a cause of high Au/Pt ratios in pyrite-bearing mineralization.…”

Section: Discussionmentioning

confidence: 99%

Platinum-group minerals of the F and T zones, Waterberg Project, far northern Bushveld Complex: implication for the formation of the PGE mineralization

et al. 2018

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This study provides the first detailed mineralogical data on platinum-group element (PGE) mineralization of the Waterberg Project, in a previously unknown segment of the Bushveld Complex located in the Southern Marginal Zone of the Limpopo Belt. The lower ultramafic F zone is dominated by sperrylite (up to 82 area%) with minor Pt–Pd bismuthotellurides, Pd–Ni arsenides, Au–Ag alloy, Rh–Pt sulfoarsenides and rare Pt–Fe alloys. The upper more felsic-rich gabbroic T zone is dominated by Pt–Pd bismuthotellurides (up to 90 area%), Pd tellurides and Au–Ag alloy with rare sperrylite, braggite, Pd stannides and antimonides. The platinum-group minerals (PGM) of the F zone are associated mainly with magmatic base-metal sulfides (pyrrhotite, troilite, chalcopyrite and pentlandite), that have undergone alteration during significant serpentinization, accompanied by the formation of the secondary sulfide assemblage. The T zone in a leucogabbroic sequence contains relics of magmatic sulfides and is characterized by the development of the indicative chalcopyrite-millerite-pyrite assemblage, which is associated with widespread hydrothermal quartz and hydrous silicates (amphiboles, phlogopite, epidote and chlorite). The fluid-induced style of PGM remobilization, the high Au/PGE and the high proportion of native gold in the high-grade T zone ores in the magnetite-bearing leucogabbroic rocks are unique to the Bushveld Complex. The genesis of the T ores is interpreted as a result of primary PGE enrichment in the zone of interaction between the first influxes of the Upper Zone fertile melt and a resident gabbroic melt at the top of the Troctolite-Gabbronorite-Anorthosite (TGA) fractionated sequence with subsequent fluid remobilization. Whether the hydrothermal overprint facilitated the PGE sequestration in a favourable setting or dispersed the pre-existing magmatic concentrations along fluid pathways remains essentially unresolved at the current stage.

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“…Perhaps, CO 2 acts as a volatile agent in hydrothermal fluid and facilitates the unmixing and separation of a vapor phase. The latter can transport an appreciable amount of gold as sulfide or chloride complexes depending on temperature and fluid chemistry (Trigub et al, 2017;Zotov et al, 2017). Phillips and Powell (2010) suggested that aqueous-carbonic low-salinity orogenic fluid can efficiently dissolve and transport gold in the form of a gold-sulphide complex, with subsequent precipitation, but is not effective to dissolve sufficient amounts of base metals, which explains the general absence of base metals at orogenic deposits.…”

Section: Systematics Of Fluid Chemical Compositionsmentioning

confidence: 99%

The sources of mineralizing fluids of orogenic gold deposits of the Baikal-Patom and Muya areas, Siberia: Constraints from the C and N stable isotope compositions of fluid inclusions

Prokofiev

Safonov

Lüders

et al. 2019

Ore Geology Reviews

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The compositions of fluid inclusions in quartz and sphalerite from five gold deposits of the Baikal-Patom (Sukhoi Log, Verninsk and Dogaldyn) and Baikal-Muya (Uryakh and Irokinda) foldbelts in the northern margin of the Central Asian Orogenic Belt, along its boundary with the Siberian craton, indicate that the gold mineralization was formed predominantly from heterogeneous CO 2-H 2 O orogenic fluid. All deposits are structurally controlled and composed of veinlet-disseminated and vein to stockwork types of ores that are hosted by rocks that underwent regional metamorphism to the greenschist facies in Baikal-Patom and up to the granulite facies in Baikal-Muya. The gold-quartz veins of all the Baikal-Patom deposits and the Uryakh were formed by fluids of similar composition with salinity of 1.4-9.5 wt % NaCl equiv. and CO 2 content of 1.4-8.6 mol/kg of solution, under comparable physical conditions, at temperatures of 128-385 ºC and pressures of 570-3290 bar. Fluids of the granulate-hosted Irokinda deposit are distinguished for the highest temperatures and pressures and involve relics of medium-to hightemperature (179-453ºC) brines with salinity of 4.6-46.3 wt % NaCl equiv. The temperature and pressure of the mineralizing fluid increase roughly from north to south, which correlates with the increase in the metamorphic grade of the host rocks. The increase is accompanied by the simultaneous systematic shift in the C isotope composition of CO 2 (released from the quartz by the chrush-leach method) from-1.9 to-5.5 ‰ δ 13 C CO2 in the Baikal-Patom and Uryakh from-0.6 to + 0.7 ‰ δ 13 C CO2 at Irokinda. The C and N isotope compositions of CO 2 suggest that Irokinda fluids were partly derived from decarbonated marine limestone, whereas the orogenic gold-bearing fluids of the other deposits are interpreted to have been composed mostly of fluid from a crustal magmatic (granitic?) source.

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Experimental modeling of Au and Pt coupled transport by chloride hydrothermal fluids at 350–450°C and 500–1000 bar

Cited by 7 publications

References 30 publications

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Gold Transport in Hydrothermal Chloride-Bearing Fluids: Insights from in Situ X-ray Absorption Spectroscopy and ab Initio Molecular Dynamics

Platinum-group minerals of the F and T zones, Waterberg Project, far northern Bushveld Complex: implication for the formation of the PGE mineralization

The sources of mineralizing fluids of orogenic gold deposits of the Baikal-Patom and Muya areas, Siberia: Constraints from the C and N stable isotope compositions of fluid inclusions

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