HCh: New potentialities for the thermodynamic simulation of geochemical systems offered by windows

Shvarov, Yu. V.

doi:10.1134/s0016702908080089

Cited by 228 publications

(104 citation statements)

References 3 publications

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“…For neutral species, it was assumed that log γ n = Γ γ = −log (1 + 0.018·m*), where m* is the sum of the concentrations of all solute species. Speciation calculations were performed by means of the Gibbs computer code of the HCh software package (Shvarov [17]). The thermodynamic properties of the aqueous species Na + , (cr) , and bunsenite NiO were taken from the SUPCRT92 database [18], and those of manganosite MnO and hausmannite Mn 3 O 4 , from Robie and Hemingway [24].…”

Section: Thermodynamic Calculationsmentioning

confidence: 99%

Stability of AuCl2− from 25 to 1000 °C at Pressures to 5000 bar and Consequences for Hydrothermal Gold Mobilization

et al. 2018

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Abstract:Gold is transported in high-temperature chloride-bearing hydrothermal fluids in the form of AuCl 2 − . The stability of this complex has been extensively studied, but there is still considerable disagreement between available experimental data on the temperature region 300-500 • C. To solve this problem, we measured the solubility of gold in HCl/NaCl fluids (NaCl concentration varied from 0.1 to 3 mol·(kg·H 2 O) −1 ) at 450 • C and pressures from 500 to 1500 bar (1 bar = 10 5 Pa). The experiments were performed using a batch autoclave method at contrasting redox conditions: in reduced experiments hydrogen was added to the autoclave, and in oxidized experiments the redox state was controlled by the aqueous SO 2 /SO 3 buffer. Hydrogen pressure in the autoclaves was measured after the experiments in the reduced system. The gold solubility constant, Au (cr) + HCl • (aq)

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Section: Thermodynamic Calculationsmentioning

confidence: 99%

Stability of AuCl2− from 25 to 1000 °C at Pressures to 5000 bar and Consequences for Hydrothermal Gold Mobilization

et al. 2018

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“…The density of water was varied from 0.02 to 0.09 g /cm 3 in the simulations and the pressure ( ) taken from the equations-of-state in the NIST database (Lemmon et al, 2000). The fugacity of water was calculated with HCh package [28] using water model of Kestin et al [29].…”

Section: Ab Initio Molecular Dynamicsmentioning

confidence: 99%

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

et al. 2018

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We investigated the hydration of the CuCl 0 complex in HCl-bearing water vapor at 350 ∘ C and a vapor-like fluid density between 0.02 and 0.09 g/cm 3 using ab initio molecular dynamics (MD) simulations. The simulations reveal that one water molecule is strongly bonded to Cu(I) (first coordination shell), forming a linear [H 2 O-Cu-Cl] 0 moiety. The second hydration shell is highly dynamic in nature, and individual configurations have short life-spans in such low-density vapors, resulting in large fluctuations in instantaneous hydration numbers over a timescale of picoseconds. The average hydration number in the second shell (m) increased from ∼0.5 to ∼3.5 and the calculated number of hydrogen bonds per water molecule increased from 0.09 to 0.25 when fluid density (which is correlated to water activity) increased from 0.02 to 0.09 g/cm 3 ( H 2 O 1.72 to 2.05). These changes of hydration number are qualitatively consistent with previous solubility studies under similar conditions, although the absolute hydration numbers from MD were much lower than the values inferred by correlating experimental Cu fugacity with water fugacity. This could be due to the uncertainties in the MD simulations and uncertainty in the estimation of the fugacity coefficients for these highly nonideal "vapors" in the experiments. Our study provides the first theoretical confirmation that beyond-first-shell hydrated metal complexes play an important role in metal transport in low-density hydrothermal fluids, even if it is highly disordered and dynamic in nature.

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“…This is because aH 2 S was initially too low to permit pyrite to form and had to be driven to higher values by The simulation was carried out using HCh modeling software (Shvarov, 2008). Thermodynamic data for pyrite was taken from Robie and Hemingway (1995), for quartz and kaolinite from…”

Section: Fluid-rock Interactionmentioning

confidence: 99%

“…The system was brought to equilibrium after the addition of each aliquot of liquid (the composition of the fluid and rocks are reported in Table 8). The simulation was carried out using HCh modeling software (Shvarov, 2008) and assumed a pressure Table 8: Composition of the fluid and rocks used in the simulation of fluid-rock interaction presented in Figure 13.…”

Section: Fluid-rock Interactionmentioning

confidence: 99%

Fumarolic Activity, Acid-Sulfate Alteration, and High Sulfidation Epithermal Precious Metal Mineralization in the Crater of Kawah Ijen Volcano, Java, Indonesia

Scher

Williams‐Jones

2013

Economic Geology

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High-sulfidation epithermal deposits are genetically associated with calc-alkaline volcanism in subduction zones, and although these ore deposits are excellent places to focus research, subduction zone stratovolcanoes provide important windows on magmatic-hydrothermal processes that are not available from study of the corresponding ore deposits. There is general agreement that the hydrothermal alteration accompanying the high-sulfidation epithermal ores is the product of volcanic degassing, however, there is considerably less agreement on the nature and origin of the ore fluid. Opinion is divided over whether the ore fluid is a vapor or a liquid, and whether it is entirely volcanic or of mixed volcanic-meteoric origin.The research presented here details a field-based investigation of the magmatic-hydrothermal environment of Kawah Ijen volcano, an active stratovolcano (mainly andesitic pyroclastics and lavas) located in the Ijen Caldera Complex in Java, Indonesia. The Kawah Ijen crater is approximately one kilometer in diameter and contains a hyperacidic lake (pH ~ -0.5) and a small and actively degassing solfatara, which is surrounded by a much larger area of acidsulfate alteration that was exposed during a phreato-magmatic eruption of the volcano in 1817; the eruption excavated the crater to a depth of 250 m. The research described in this thesis involved sampling and chemical analyses of the gases and their condensates (the surface equivalents of the ore-forming magmatichydrothermal fluids) collected from the solfatara and rock samples taken from the alteration center.Condensed fumarolic gases (pH ~ -0.5) released from the solfatara and sampled at temperatures between 330 and 495 °C contain up to 3 ppm Cu and 3.8 ppm As; the concentration of Ag is below detection. The alteration center is characterized by zones of residual silica, alunite-pyrite and kaolinite/dickite; based on alunite-pyrite geothermometry, the area formed at a temperature between 200 and 300 °C. High sulfidation epithermal mineralization occurs in this area in the form of massive and vein-hosted pyrite that contains up to 200 ppb iii Au, 16 ppm Ag, 6,800 ppm Cu, and 3,430 ppm As; these elements are invisible at the highest resolution of scanning electron microscopy, and thus occur either in the form of nano-particles or are in solid solution in the pyrite.The manuscript in Chapter 3 summarizes the observations detailed above to support a model in which highly acidic gases condensed ~ 250 m beneath the floor of the pre-1817 crater at Kawah Ijen volcano. In the area near the source of the vapors, the ratio of fluid to rock was extremely high and resulted in the leaching of elements from the andesitic host rock, leaving behind a residue of "vuggy silica." With increasing distance from the source, in an area of intermediate fluid/rock ratio, the condensed liquids replaced the primary minerals of the host with alunite and pyrite. The kaolinite/dickite zone formed in a rockbuffered environment (low fluid/rock ratio), in the zone furthest fr...

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HCh: New potentialities for the thermodynamic simulation of geochemical systems offered by windows

Cited by 228 publications

References 3 publications

Stability of AuCl2− from 25 to 1000 °C at Pressures to 5000 bar and Consequences for Hydrothermal Gold Mobilization

Stability of AuCl2− from 25 to 1000 °C at Pressures to 5000 bar and Consequences for Hydrothermal Gold Mobilization

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

Fumarolic Activity, Acid-Sulfate Alteration, and High Sulfidation Epithermal Precious Metal Mineralization in the Crater of Kawah Ijen Volcano, Java, Indonesia

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