Natural fluid phases at high temperatures and low pressures

doi:10.1016/S0375-6742(97)00041-1

Journal of Geochemical Exploration

Volume 62, Issues 1–3, June 1998, Pages 183-191

https://doi.org/10.1016/S0375-6742(97)00041-1 Get rights and content

Abstract

Gas phases at low pressures and high (magmatic) temperatures have certain peculiar properties. The fluid is mainly water vapour, which is usually observed during discharging of crystal magmatic melts. At >700°C and <100 bar these peculiar properties include: formation of near `dry' salt melts as second fluid phase, very strong fractionation of hydrolysis products between vapour and melts, subvalence state of metals during transport processes, and high sensitivity of the gas to conditions of sublimate precipitation. Phase diagram analysis as well as results of field and laboratory experiments are presented in this article. The processes could be a model for industrial technologies to clean wastes from toxic, rare and heavy metals. Transport forms of some elements in volcanic gases are very similar to the species which were formed first in the protosolar nebula.

Introduction

Gas pollution is a serious problem in modern environments and will only increase in the next century. The principles of geochemical engineering, i.e. the organisation of industrial processes to protect our environment by the same way as natural processes (Schuiling, 1990), could be applied to clean industrial gases from heavy, toxic and rare elements, but we must know how these natural processes are regulated. The best way to investigate these processes is by studying volcanic gases which contain practically all elements, and these compositions can be used as a model for industrial gas pollution. This article is a short review of new field and laboratory results which were obtained from the Kudriavy volcano (andesitic Kuril Island Arc, Russian Far East) from 1988 to 1996, where very hot fumaroles of 170–940°C exist in a stationary regime dating from the last explosion in 1873. The main analytical and mineralogical data for the fumarole gases and sublimates are published by Korzhinsky et al., 1994, Korzhinsky et al., 1995, Korzhinsky et al., 1996and Taran et al. (1995); some of the data are still in preparation. These high-temperature fumaroles have relatively constant compositions of 94–95 mol% of H₂O, about 2 mol% each of various C and S species and 0.5 mol% HCl. A maximal H₂ concentration of 1.2 mol% was found in the hottest fumarole (940°C). Oxygen fugacities were found to fall within the `inner' gas buffer, which mainly depend on the temperature of equilibrium between sulphuric species (SO₂, H₂S, S), H₂ and H₂O. This equilibrium is very near to the Ni–NiO buffer, which can be used for calculations. Calculation of oxygen fugacities using the ratios SO₂/H₂S and CO₂/CO are in good agreement with direct measurements of f_O₂ by solid state electrolyte cells (Rosen et al., 1993)

Section snippets

L–V equilibrium

Degassing of a magmatic melt at low pressure can take place if the magma chamber is in connection with the surface via gas conduits, and the pressure on the uppermost part of the chamber is not too large. Gas viscosity and, consequently, gasodynamic resistance are small and for conduits with a characteristic size of 1–10 cm, the Darcy equation indicates only a pressure of 5–20 bar on the magma surface at intermediate crust chambers, 2–3 km under the volcanic summit. Stable isotope data for D/H

Hydrolysis of the salt melt

At a liquid–vapour equilibrium, if the vapour phase is practically pure water, we should observe the effect of the fractionation of the hydrolysis products between coexisting phases. One such simple reaction is: H₂O+NaCl=HCl+NaOH. At high pressure (above 500 bar) this reaction has a strong shift to the left, but at magmatic temperatures and low pressures (below 100 bar) the process of fractionation begins to play an important role. The fugacities (or vapour pressures) of HCl and NaOH differ

Sublimate minerals formation

Long-time experiments for sublimate formation were done on the Kudriavy volcano. Maximal duration of the runs was nearly 1 month. The sublimates precipitated inside quartz glass tubes, 2/3 of which was exposed above the surface and 1/3 was buried below. In the tubes were found: halogenides (simple as NaCl and KCl, and more complicated KPb₂Cl₅, marshite, CuI, and some fluorine minerals), oxides (SiO₂, Al₂O₃, KReO₄), sulphides, silicates and sulphates. Detailed description of sublimate mineralogy

Native elements

Some native elements are quite common in rocks, e.g. noble metals, sulphur, iron, carbon, etc. In the Russian literature since 1981, many articles were published about quite unusual native metals (Al, Si, Mg, Bi, Pb) in kimberlites, trapps, granites and hydrothermal ore deposits (Novgorodova, 1983). Calculations concerning the stability fields of these metals lead to unrealistic fluid compositions (Novgorodova, 1996), which were practically pure methane or hydrogen. However, the many

Vapour phase species

Calculations for metal transport by volcanic gases were done for the Momotombo (Quisefit et al., 1989), Augustin (Symonds et al., 1992) and St. Helens volcanoes (Symonds and Reed, 1993). From the database and software of Symonds and Reed (1993)the main species in those gases for rock-forming and ore elements include chlorides (MnCl₂, CoCl₂, CuCl, AgCl, KCl, NaCl, RbCl, CaCl₂, CsCl), (hydr-)oxides (Fe(OH)₂, H₂WO₄, H₂MoO₄), elements (Zn, Cd, Hg), sulphides (PbS, AsS, SbS, AuS), and fluorides (SiF₄

Mass transport by gases

During the 1995 field season on the Kudriavy volcano COSPEC measurements were done by S. Williams and T. Fisher (Arizona State University, pers. commun., 1995). The bulk emission of magmatic gases was estimated at about 2000 metric tons per day. Surface mapping of the fumarole fields and measurement of gas velocities in the jets and in the steam areas have suggested that this value is an order of magnitude higher. However, these measurements have included meteoric as well as magmatic water. In

Conclusions

Long-term investigations of sublimate precipitation of main and trace elements using optic, SEM and microprobe studies, analysis of volcanic gases and geochemical modelling of transport forms have been carried out on the Kudriavy volcano, which produces approximately 2000 tons/day of magmatic gases. The sublimates precipitated in quartz glass tubes as practically monomineral clusters. This process could be a model for industrial technologies to separate toxic, rare and heavy metals from waste.

Acknowledgements

We are thankful for the support of the fieldwork on the Kudriavy volcano by the Russian Fund of Basic Investigations, the Russian Ministry of Sciences and Technology and, furthermore, the organizing committee of the Geochemical Engineering Symposium for the opportunity to participate. Many thanks to Daniel Harlov and Hans Zijlstra for corrections of our terrible English.

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Cited by (25)

Chalcocite Cu<inf>2</inf>S solubility in aqueous sulfide and chloride fluids. Thermodynamic properties of copper(I) aqueous species and copper transport in hydrothermal systems
2023, Chemical Geology
The most important Cu reserves, including ores of porphyry deposits, were formed by Cl- and S-bearing hydrothermal fluids transporting and depositing metals within the magmatic-hydrothermal ore systems. In order to determine the state of Cu in the fluids, we measured the solubility of chalcocite Cu₂S at 350 and 450 °C, 500 and 1000 bar. The concentration of H₂S varied from 0.08 to 0.4 m [mol⋅(kg H₂O)⁻¹], NaOH – from 0 to 0.2 m, NaCl + HCl – from 0.01 to 4 m. The solubility of chalcocite can be described by the reactions:
0.5 Cu₂S_(cr) + 0.5 H₂S_(aq) = CuHS_(aq) log K°_CuHS = −3.99 ± 0.07 (350 °C/500 bar)
−4.61 ± 0.09 (450 °C/500 bar), −4.26 ± 0.11 (450 °C/1000 bar);
0.5 Cu₂S_(cr) + 0.5 H₂S_(aq) + HS⁻ = Cu(HS)₂⁻ log K°_Cu(HS)2- = −0.85 ± 0.08 (350 °C/500 bar)
−0.65 ± 0.11 (450 °C/1000 bar);
0.5 Cu₂S_(cr) + HCl_(aq) = CuCl_(aq) + 0.5 H₂S_(aq) log K°_CuCl = −3.11 ± 0.70 (450 °C/1000 bar);
0.5 Cu₂S_(cr) + HCl_(aq) + Cl⁻ = CuCl₂⁻ + 0.5 H₂S_(aq) log K°_CuCl2- = 0.33 ± 0.19 (450 °C/1000 bar)
These results, together with data of Rubtsova et al. (2023) on the coupled solubility of Cu_(cr) and Ag in chloride fluids, demonstrated that a simple extended Debye-Hückel equation describe activity coefficients of charged species at any NaCl concentration up to the solubility limit at near- and supercritical PT-parameters; activity coefficients of neutral species can be calculated with Setchenov parameter equal to zero. The Cu₂S_(cr) solubility in sulfide-chloride-bearing fluids is consistent with the formation of Cu-Cl complexes which implies that mixed Cu-HS-Cl complexes can be neglected. The experimental values pooled with the reliable literature data were fitted to the HKF (Helgeson-Kirkham-Flowers) model equation of state (EoS). The obtained HKF EoS parameters allow to predict thermodynamic properties of CuHS_(aq), Cu(HS)₂⁻, and CuCl_(aq) from 25 to 700 °C and from P_sat. to 2000 bar, and up to 1000 °C/5000 bar for CuCl₂⁻. The AD (Akinfiev and Diamond) EoS parameters were derived for CuCl_(aq). The AD EoS can be used to calculate the CuCl_(aq) Gibbs free energy in the low-density fluids (ρ_H2O < 0.35 g⋅cm⁻³) up to 700 °C. The obtained thermodynamic data imply that CuCl₂⁻ predominates in high-density ore-forming fluids (ρ_H₂O > 0.35 g⋅cm⁻³) of total chloride content >0.1 wt% up to the NaCl saturation limit. The hydrosulfide complexes are the main forms of Cu occurrence in the fluid with concentration of dissolved chlorides <0.1 wt% equilibrated with silicate mineral assemblages (e.g., K-feldspar-muscovite-quartz, pH is near-neutral). However, their concentration in the presence of Cu-bearing sulfides is low (< 0.5 ppm at 500 °C/1500 bar) and decreases with temperature decreasing.
Chlorine and felsic magma evolution: Modeling the behavior of an under-appreciated volatile component
2020, Geochimica et Cosmochimica Acta
Citation Excerpt :
The resultant brine is available for subsequent interactions with other fractions of melt either via complete assimilation or disequilibrium exchange of Cl as magma convects and/or as saline fluids ascend through magma. Brines should ascend because they have lower densities than melt (Shmulovich and Churakov, 1998). It follows that assimilation processes may explain the steeply negative and dispersed trends shown by glasses from Mt. Jang, for some MI of the topaz rhyolitic systems, for Climax/Chalk Mountain MI, and for most MI of the Bandelier Tuff (Fig. 9B and C).
Research on magmatic Cl has proven useful for understanding melt evolution, degassing, and other igneous processes. Magmatic Cl behavior varies strongly with its solubility in melt, and Cl solubility and its partitioning between melts and fluids vary with the Cl content of the system, melt composition, pressure, and the abundance of oxidized magmatic sulfur. Given these relationships and given that they differ from other magmatic volatiles, Cl can provide unique insights on magma evolution. We present a new method of interpreting melt Cl concentrations that are normalized to their calculated Cl solubilities, and the most accurate results apply to solubilities computed at 200 MPa due to insufficient experimental data for other pressures. We apply the new method to compositional data for more than 3500 dacitic to rhyolitic melt inclusions and matrix glasses, representing 64 felsic igneous systems, to demonstrate how the behavior of Cl during magmatic, magmatic-hydrothermal, and degassing processes can be more accurately interpreted.
Variations in Cl for most of the 64 systems agree with modeled Cl behavior indicative of melt evolution dominated by fractional crystallization of fluid(s)-saturated melts, and the majority of these systems were apparently saturated in fluid(s) well before melt inclusion entrapment. Comparison of Cl solubility-normalized Cl concentrations of these glasses with modeled results identifies magmas saturated in hydrosaline liquid ± vapor at pressures as high as 600 MPa. Modeling of pressure reductions from 600 down to 20 MPa distinguishes other magmas that exsolved hydrosaline liquid as magmas ascend to shallower depths. This new approach also supports computation of Cl concentrations of magmatic fluids at 200 MPa, for each of the >3500 glasses, and shows how the Cl contents of fluids vary with the (fluid/melt) mass ratio. For example, Cl contents of magmatic fluids range from 0.3 to nearly 70 wt.% at fluid/melt mass ratios of 2 × 10⁻³, and from 0.3 to a maximum of only 11 wt.% Cl for fluid/melt mass ratios of 4.2 × 10⁻².
Compositional trends in the glass data show either increasing Cl contents of residual melt, essentially no change of Cl in melt, or decreasing Cl contents of aliquots of residual melt with progressive melt evolution. This method identifies melts that have assimilated magmatic or externally sourced hydrosaline liquids. Plots of (measured Cl in melt/modeled solubility of Cl in melt; Cl[Me/Mo]) versus the Larsen melt differentiation index show minimal dispersion for the least-evolved dacitic melts and increasing dispersion with melt evolution to rhyolitic compositions. Increased dispersion may be a consequence and indication of equilibrium or non-equilibrium degassing and/or assimilation of hydrosaline liquid.
Platinum transport in chloride-bearing fluids and melts: Insights from in situ X-ray absorption spectroscopy and thermodynamic modeling
2019, Geochimica et Cosmochimica Acta
Citation Excerpt :
Some examples of these thermodynamic calculations are given in the following sections. Anhydrous chloride salt melts as a reservoir which accumulates metals at the upper part of degassing magma chamber beneath volcanoes was suggested by Shmulovich and Churakov (1998) and Shmulovich et al. (2016) to explain formation of the metal-rich fumarolic products. For example, Pd-Pt selenide and native Pt were discovered in artificial fumarolic precipitates sampled at Kudryavy volcano (Kurile Islands) (Korzhinsky et al., 1996; Yudovskaya et al., 2006).
Hydrothermal chloride-rich fluids are identified at the late stages of the formation of platinum group element (PGE) deposits in giant layered intrusions, and are considered as the PGEs transport media in Cu(-Mo,Au) porphyry systems. In order to quantify the hydrothermal mobility of Pt we performed an investigation of the speciation of Pt in hydrothermal chloride-bearing fluids and dry melt by means of X-ray absorption spectroscopy (XAS). The experiments consisted in recording the Pt L₃-edge X-ray absorption near edge structure/extended X-ray absorption fine structure (XANES/EXAFS) spectra of Pt-bearing fluids obtained by dissolution of Pt metal in KCl/HCl and CsCl/HCl fluids in the temperature range from 450 to 575 °C at pressures from 0.5 to 5 kbar. A spectrum of Pt dissolved in dry CsCl/NaCl/KCl + K₂S₂O₈ melt was recorded at 650 °C. The capillary method, when the experimental solution together with Pt_(cr) is sealed inside a silica glass capillary, was used. As was determined from the XANES spectra, in all the experimental systems Pt existed in the +2 oxidation state. Analysis of EXAFS spectra showed that Pt is coordinated by four Cl atoms with R_Pt-Cl = 2.31 ± 0.01 Å independently of the T-P-compositional parameters. No evidence of the formation of complex with alkali metal cations in the second coordination sphere of Pt was found by the analysis of the EXAFS spectra of concentrated CsCl brines and melt. Our results imply that PtCl₄²⁻ is the main Pt-Cl complex which predominates in hydrothermal fluids at t > 400 °C and fluid density d > 0.3 g·cm⁻³. Experimental data obtained for dry melt of alkali metal chlorides suggest that Pt-Cl complexes can dominate Pt speciation in chloride-bearing aluminosilicate melts where Cl exhibits a salt-like atomic arrangement and ionic bonding. The literature data on the Pt solubility constant, ${P t}_{(c r)} + {2 H C l}_{(a q)}^{o} + {2 C l}^{-} = {P t C l}_{4}^{2 -} + H_{2_{(a q)}}$ , are compiled and fitted to the simple density model equation $\log K_{s}^{o} ({P t C l}_{4}^{2 -}) = 0.973 - 8202 {\cdot T (K)}^{- 1} - 5.505 \cdot \log d (w) + 2223 \cdot \log d (w) \cdot {T (K)}^{- 1}$ , where d(w) is the pure water density in g·cm⁻³. The equation, combined with the extended Debye-Hückel equation for activity coefficients, can be used to calculate the solubility of Pt up to 1000 °C/5 kbar. It accurately predicts the solubility of Pt in concentrated chloride brine (up to 50 wt% NaCl) at parameters of magmatic-hydrothermal transition (800 °C/1.4 kbar). At fluid/vapor density below 0.3 g·cm⁻³ a neutral complex PtCl₂°_(aq) is suggested as the dominant Pt species. Our data demonstrate that Pt is highly mobile in high-temperature oxidized chloride-rich hydrothermal fluids. For example, at 800 °C/2 kbar the concentration of Pt can reach a few wt% in the 1 wt% HCl/50 wt% NaCl fluid which is in equilibrium with magnetite-hematite buffer. Once a Cl-reach fluid exsolves from alumuinosilicate melt, Pt follows Cl and enriches the fluid phase where it exists mostly in the form of PtCl₄²⁻. Decrease of temperature, acidity, and fluid chlorinity results in precipitation of Pt from the fluid phase.
Evidence for aqueous liquid-liquid immiscibility in highly evolved tin-bearing granites, Mount Pleasant, New Brunswick, Canada
2017, Chemical Geology
Citation Excerpt :
With the available data, we cannot, however, rule out a co-genetic model for the two, whereby they were both exsolved from the same granitic magma. This model in general supports the experimental data of Shmulovich and Churakov (1998), Veksler et al. (2002), Veksler and Thomas (2002), Veksler (2004), and Veksler (2005), and can be considered a natural example of their research. The fluids responsible for Sn mineralization in the North Zone at Mount Pleasant are represented by primary LV fluid inclusions in cassiterite (Elmi Assadzadeh, 2014).
Three distinct types of fluid inclusions (i.e., liquid + vapor (LV), liquid + vapor + solid (LVS), and V-only) co-exist within a single, primary fluid inclusion assemblage in fluorite crystals that formed prior to and in close association with cassiterite mineralization in an assemblage comprising fluorite + arsenopyrite + topaz + cassiterite in the Sn (-W-Mo) deposit of the North Zone, Mount Pleasant, New Brunswick. The mineral assemblage occurs in vugs, with late quartz and chlorite filling the remainder of the open space. Solid-bearing inclusions contain up to eight, optically different solids, which are estimated to occupy up to approximately 70 vol.% of the fluid inclusions. In a given fluid inclusion assemblage, each type of fluid inclusion shows consistent L-V or L-V-S phase ratios.
The results of microthermometric analyses show that LV inclusions have low salinities that vary from 0 to 10 wt.% NaCl eq., and homogenization temperatures that vary from 91 to 250 °C. Within a given assemblage, the ranges of salinity and homogenization temperatures of LV inclusions are even less. In contrast, co-existing LVS inclusions are highly saline, with salinities ranging from 36 to 40 wt.% NaCl eq., and have much higher homogenization temperatures that vary from 425 °C to > 600 °C (the upper limit of the microthermometric stage). The salinity and homogenization temperature ranges of LVS inclusions show a limited range for a given assemblage. The solids in LVS inclusions are interpreted as daughter phases due to consistent phase ratios in LVS fluid inclusions and because, during heating experiments, all solid phases melted prior to liquid-vapor homogenization. The consistency of phase ratios and the results of microthermometric analysis among LV or among LVS inclusions show that these inclusions were not formed through necking down of larger inclusions. In addition, the absence of ‘sweat halos’ and re-entrants rules out water loss as a possible mechanism for producing these coexisting fluid inclusions. Fluid inclusions of highly contrasting salinities and homogenization temperatures are, therefore, interpreted to be the result of trapping from two, immiscible, aqueous liquids. It is unknown whether the two liquids exsolved from one single, aqueous fluid or have different origins, but consideration of the nature of inclusion assemblages in samples from other parts of the system, suggest the latter. Topaz and cassiterite within the same mineral assemblage, as well as late quartz, contain LV fluid inclusion assemblages with microthermometric behaviors that are similar to the LV type inclusions in coexisting, fluorite-hosted, LV and LVS inclusions, suggesting that cassiterite deposited from the low salinity and temperature fluid.
Solubility and fluid-melt partitioning of H<inf>2</inf>O and Cl in andesitic magmas as a function of pressure between 50 and 500 MPa
2015, Chemical Geology
This study presents experimental data on the partitioning of Cl between andesitic melt and H₂O- and Cl-bearing fluids at 1200 °C and at 50 to 500 MPa. The results demonstrate that at isothermal conditions Cl partitioning is governed by pressure, Cl and H₂O content in the system affecting mixing properties of the fluid phase. The maximum Cl contents in the melt reach ~ 2.5 wt.% Cl at P < 200 MPa and about 3–3.5 wt.% Cl at P > 300 MPa in a good agreement with recent model (Webster et al., 2015. Experimental and modeled chlorine solubilities in aluminosilicate melts at 1 to 7000 bars and 700 to 1250 °C: Applications to magmas of Augustine Volcano, Alaska. Am. Mineralogist, 100: 522–535). Water solubility in the melt increases from 1.4 to 10 wt.% with pressure increase from 50 to 500 MPa and can be described by a power law: H₂O (wt%) = 0.0659 · P^0.8184 (R² = 0.98). Moreover, there is a positive correlation between water and Cl contents of the melt at P < 200 MPa with an increase of maximum water concentration by a factor of 2 at 50 MPa in the range 0 to ~ 2 wt.% Cl. Both increasing pressure and increasing Cl content in the system enhance partial dissolution of the melt into the fluid (mainly by extraction of Ca, Na and K) resulting in large uncertainty of fluid composition determination. However, based on well-defined systematic trends and observed general relationships between Cl + cation + H₂O contents in the melt and fluid phases, the systems at P < 200 MPa can be characterized by the occurrence of fluid immiscibility (vapor + brine), whereas at P > 300 MPa a single supercritical fluid is considered. Surprisingly, vapor phase at P < 200 MPa can contain up to 35–40 wt.% Cl + Σcations indicating that the immiscibility gap in andesitic system is dramatically reduced when compared with that of simple water–salt fluids or silicic melt + fluid systems. Despite observed differences in fluid characteristics at low and high P, fluid–melt partition coefficients of Cl (D_Cl) show similar non-linear evolution as a function of Cl content in the melt up to 2 wt.% and vary between ~ 1 and ~ 12 (on mass basis). Furthermore, systems with Cl content in the melt < 1 wt.% follow Henrian behavior and considering only reproducibility errors for this range, their averaged D_Cl values demonstrate a pronounced minimum at around 2 at 200 MPa. A negative pressure dependence of D_Cl between 50 and 200 MPa can be described by a power law D_Cl = 279.92 · P^− 0.914 (R² = 0.95), whereas a positive correlation with P between 200 and 500 MPa can be fitted by an exponential function: D_Cl = 1.0444 · e^0.004 · P (R² = 0.97). The observed change in the D_Cl trend is presumably attributed to the changes in Cl speciation in the fluid, i.e., from acidic HCl-dominated fluids at low P to basic cation-dominated fluids at high P which might be also responsible for the significant decrease in the fluid immiscibility gap at P < 200 MPa. The compilation of experimental data on Cl partitioning illustrates that silicic peralkaline magmas typically have up to an order of magnitude higher D_Cl at P > 200 MPa but may have comparable D_Cl at P < 200 MPa than the D_Cl of more mafic and metaluminous magmas.
Native gold from volcanic gases at Tolbachik 1975-76 and 2012-13 Fissure Eruptions, Kamchatka
2015, Journal of Volcanology and Geothermal Research
Citation Excerpt :
The etched rounded morphology of some crystals in the Tolbachik samples indicates a disequilibrium between gas unsaturated in gold and sublimates while crystallization of perfect crystals was supported by a local saturation and gas transport reactions. The important features of gas transport reactions are 1) most metals and their various compounds (oxides, salts, sulfides, sulfosalts) can be transported; 2) crystallization temperature of metal compounds from gas is lower than that from a melt; 3) various gases such as halogens, hydrogen, oxygen, water and chlorides can be carriers; 4) compounds of the same element with different valence states can co-exist and intergrow (Shmulovich and Churakov, 1998; Yudovskaya et al., 2008); 5) parameters and morphology of growing crystals are controlled by parameters of the medium. Еxperimental data on gold solubility indicate Au concentration less than 0.5 ppb in the H2S–S–H2O vapor systems at 300–360 °C, and Au volatility increases in the presence of water that is explained by increasing solvation of Au species (Zezin et al., 2011).
Aggregates and euhedral crystals of native gold were found in sublimates formed during New Tolbachik Fissure Eruption in 2012–2013 (NTFE). Gold-bearing sublimate samples were taken from a red-hot (690 °C) degassing fracture in the roof of an active lava tunnel 1.5 km from active Naboko cinder cone in May 2013. The gas condensate collected at 690 °C in this site contains 16 ppb Au, 190 ppb Ag and 1180 ppm Cu compared to 3 ppb Au, 39 ppb Ag and 9.7 ppm Cu in the condensate of pristine magmatic gas sampled at 1030 °C. The 690 °C volcanic gas is most likely a mix of magmatic gas and local snow buried under the lava flows as indicated by oxygen and hydrogen isotope compositions of the condensate. The lower-temperature gas enrichment in gold, copper and chlorine is resulted from evaporation of the 690 °C condensate during forced gas pumping at sampling. Native gold was also found in fumarolic encrustations collected from caverns in basalt lava flows with temperature up to 600 °C in June 2014, in a year after eruption finished.
The native gold precipitation in newly formed Cu-rich sublimates together with the well known gold occurrences in cinder cones of 1975–1976 Large Tolbachik Fissure Eruption manifest a transport capability of oxidized volcanic gas.

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¹: Permanent address: Institute of Experimental Mineralogy RAS, 142432 Chernogolovka, Russia.

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Natural fluid phases at high temperatures and low pressures

Abstract

Introduction

Section snippets

L–V equilibrium

Hydrolysis of the salt melt

Sublimate minerals formation

Native elements

Vapour phase species

Mass transport by gases

Conclusions

Acknowledgements

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Appl. Geochem.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Liquid–vapor relations for the system NaCl–H2O: summary of the PTX surface from 300° to 500°C

Am. J. Sci

The influence of the fluid phase composition on the solidus temperatures in the haplogranite system NaAlSi3O8–KAlSi3O8–SiO2–H2O–CO2

Contrib. Mineral. Petrol.

Chlorides of sodium and calcium as a possible source of acid media at depth

Dokl. Akad. Nauk SSSR

Discovery of a pure rhenium mineral at Kudriavy volcano

Nature

Liquid–vapor relations for the system NaCl–H²O: summary of the PTX surface from 300° to 500°C

The influence of the fluid phase composition on the solidus temperatures in the haplogranite system NaAlSi₃O₈–KAlSi₃O₈–SiO₂–H₂O–CO₂