The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

Bessinger, Brad; Apps, John A.

doi:10.2172/840338

Cited by 7 publications

(3 citation statements)

References 62 publications

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“…NiCl + , NiCl 2 (aq), and NiCl 3 − from Liu et al (2012) were implemented using the Ryzhenko parameters and the Thermoddem database temperature-dependent dissociation of H 2 O to further increase internal consistency. The added aqueous Sb species were taken from Obolensky et al (2007) and augmented by the compilation of Bessinger and Apps (2003).…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

The formation of (Ni-Co-Sb)-Ag-As ore shoots in hydrothermal galena-sphalerite-fluorite veins

et al. 2021

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Unusual hydrothermal native As-sulfide ± native Ag ± arsenide ± antimonide ± sulfosalt ore shoots and their co-genetic sulfide-fluorite-barite-quartz host veins, which are common in the region and in whole Central Europe, were investigated at three localities in the Schwarzwald, SW Germany, to understand the physico-chemical processes governing the change from a normal (= common) hydrothermal to an exceptional ore shoot regime. Based on fluid inclusions, the formation of the gangue minerals is the result of binary mixing between a NaCl-rich brine and a CaCl2-rich brine (both ~ 20 wt% NaCl aq.). This mixing correlation, major and minor fluid composition, formation temperature (~ 150 °C), and δ34S signature are identical (within error) in ore shoots and host veins. Thermodynamic modeling indicates that ore shoot formation must have resulted from a change in redox conditions by a local influx of a volumetrically minor reducing agent, probably hydrocarbons. The elemental content and the mineralogy of each ore shoot locality (Ag-As-rich: Münstertal; Ag–Ni-As-rich: Urberg; Ag–Ni-As-Sb-rich: Wieden) reflect the metal content of the binary mixed fluid, while mineral textures, successions, and assemblages are thermodynamically and, regarding sulfur, kinetically controlled. The formation of vein and ore shoot sulfides requires an addition of sulfide, most probably from the sulfide-bearing host rocks, because thermodynamic and kinetic reasons suggest that the two major vein-forming and metal-bearing fluids are not the source of the sulfur. The final ore shoot textures are influenced by later hydrothermal remobilization processes of As and Ag. This results in a number of sulfosalts, mostly proustite-pyrargyrite. Interestingly, the greater thermodynamic stability of Sb-endmember sulfosalts enables them to form even in As-dominated fluid systems.

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Section: Thermodynamic Modelingmentioning

confidence: 99%

The formation of (Ni-Co-Sb)-Ag-As ore shoots in hydrothermal galena-sphalerite-fluorite veins

et al. 2021

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“…A detailed description of computational algorithms was given in [34]. The models used thermodynamic databases in the range of specified T-P parameters: for minerals [35][36][37][38][39][40][41][42], gases [43], and components of aqueous solution [44][45][46][47][48][49][50][51][52].…”

Section: Software and Thermodynamic Dataset For Modelingmentioning

confidence: 99%

Formation of Au-Bearing Antigorite Serpentinites and Magnetite Ores at the Massif of Ophiolite Ultramafic Rocks: Thermodynamic Modeling

et al. 2019

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We constructed thermodynamic models of the formation of two types of gold-ore mineralization at the Kagan ultramafic massif in the Southern Urals (Russia). The first type of gold-mineralization is widely spread at the massif in the tectonic zones of schistose serpentinites containing typically ≤ 0.1 ppm Au. The second type of gold-ore mineralization is represented by veined massive, streaky and impregnated magnetite ores in contact with serpentinites. It contains to 5 vol.% sulfides and 0.2–1.2 ppm Au. Our thermodynamic calculations explain the formation of two types of gold-ore mineralization in the bedrocks of ultramafic massifs. Metamorphic water, which is the result of the dehydration of early serpentinites (middle Riphean) during high-temperature regional metamorphism (700 °C, 10 kbar) (late Precambrian), is considered as the source of ore-bearing fluid in the models. The metasomatic interaction of metamorphic fluid with serpentinites is responsible for the gold-poor mineralization of the 1st type at T = 450–250 °C and P = 2.5–0.5 kbar. The hydrothermal gold-rich mineralization of the 2nd type was formed during mixing of metamorphic and meteoric fluids at T = 500–400 °C and P = 2–3 kbar and discharge of mixed fluid in the open space of cracks in serpentinites. The model calculations showed that the dominant forms of gold transport in fluids with pH = 3–5 are AuCl2− complexes (≥450 °C) and, as the temperature decreases, AuHS0, or AuOH0. Mineral associations obtained in model calculations are in general similar to the observed natural types of gold mineralization.

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“…The reasons behind this adjustment are not clear. Bessinger and Apps (2005) modified the fG o from Barton (1969) slightly and took S o from Barton (1969), even though they referred to Pokrovski et al (1996) as their data source. Stolyarova (1977).…”

Section: Introductionmentioning

confidence: 99%

Calorimetric study of skutterudite (CoAs2.92) and heazlewoodite (Ni3S2)

Majzlan

Kiefer

Lilova

et al. 2022

American Mineralogist

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Nickel and cobalt arsenides, sulfarsenides, and sulfides occur in many hydrothermal ore deposits but the thermodynamic properties of these phases are not well known, in some cases not known at all. In this work, we determined a full set of thermodynamic properties for heazlewoodite and skutterudite. Both phases were synthesized in evacuated silica tubes at elevated temperatures and electron microprobe analyses gave their composition as Ni3S2 and CoAs2.92, respectively. Enthalpies of formation were measured by high-temperature oxidemelt solution calorimetry. The reference phases were pure elements, thus eliminating any systematic errors related to such phases. The enthalpies of formation at T = 298.15 K and P = 10 5 Pa are -216.0±8.4(2) and -88.2±6.1 kJ•mol -1 for Ni3S2 and CoAs2.92, respectively. Entropies were calculated from low-temperature heat capacity (Cp) data from relaxation (PPMS) calorimetry and are 133.8±1.6 and 106.4±1.3 J•mol -1 •K -1 , respectively. The calculated Gibbs free energies of formation are -210.0±8.4 and -79.9±6.2 kJ•mol -1 for Ni3S2 and CoAs2.92, respectively. The PPMS Cp data, together with a set of differential scanning calorimetry This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

Cited by 7 publications

References 62 publications

The formation of (Ni-Co-Sb)-Ag-As ore shoots in hydrothermal galena-sphalerite-fluorite veins

The formation of (Ni-Co-Sb)-Ag-As ore shoots in hydrothermal galena-sphalerite-fluorite veins

Formation of Au-Bearing Antigorite Serpentinites and Magnetite Ores at the Massif of Ophiolite Ultramafic Rocks: Thermodynamic Modeling

Calorimetric study of skutterudite (CoAs2.92) and heazlewoodite (Ni3S2)

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