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Article

Geochemistry and Fluid Inclusion of Epithermal Gold-Silver Deposits in Kamchatka, Russia

by
Maria Shapovalova
*,
Elena Shaparenko
and
Nadezhda Tolstykh
Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia
*
Author to whom correspondence should be addressed.
Minerals 2025, 15(1), 2; https://doi.org/10.3390/min15010002
Submission received: 20 November 2024 / Revised: 17 December 2024 / Accepted: 21 December 2024 / Published: 24 December 2024
(This article belongs to the Special Issue Mineralogy, Geochemistry and Fluid Inclusion Study of Gold Deposits Endowed in Critical Metals)
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Abstract

:
The work focuses on five epithermal Au-Ag deposits of the Kamchatka volcanogenic belts: Rodnikovoe, Baranyevskoe, Kumroch, Lazurnoe (adularia-sericite type–Ad-Ser) and Maletoyvayam (acid-sulfate type–Ac-Sul). The geochemical characteristics of the deposits were presented based on the results of ICP-OES and fire-assay analysis. The compositions and physicochemical parameters of ore-forming fluids were based on microthermometry, Raman spectroscopy and gas chromatography-mass spectrometry. It was shown that all deposits were comparable in terms of temperatures, salinity and the predominance of H2O and CO2 in ore-forming fluids. The deposits were formed at temperatures of 160–308 °C by aqueous fluids with salinities of 0.5–6.8 wt. % (NaCl-eq.). The Maletoyvayam deposit differed from the other ones in significant enrichment in Se, Te, Sb, Bi and As, as well as much higher concentrations of hydrocarbons, nitrogenated and sulfonated compounds (31.4 rel.% in total) in the composition of fluid inclusions. This gave us a reason to assume that organic compounds favourably affected the concentrations of these elements in the mineralising fluid. Kumroch and Lazurnoe were distinguished from Rodnikovoe and Baranyevskoe by high Zn, Pb and Cu contents, where each of them represented a single system combining both Ad-Ser type epithermal gold-silver and copper porphyry mineralisations. The presence of alkanes, esters, ketones, carboxylic acids and aldehydes in different quantities at all deposits were indicators of the combination of biogenic and thermogenic origins of organic compounds. The contents of ore-forming elements in ores were consistent with the specificity of mineral assemblages in the Kamchatka deposits.

1. Introduction

Epithermal deposits of gold and silver play a significant role in the world balance of ores of these metals. This type of deposit accounts for up to 8% of global gold production [1]. In addition to gold and silver, the ores of epithermal deposits contain associated Au and Ag chalcogenides, which are important concentrators of Se and Te [2]. As Se and Te have been increasingly in demand for high-tech industries in recent years [3], the study of Se and Te distribution in ores of Kamchatka epithermal deposits (Figure 1), as components associated with extraction, is therefore of significant practical importance.
Determining the conditions of formation of epithermal deposits is one of the main problems of the theory of endogenous ore formation [4], which has long been successfully solved on the basis of studying the parameters of ore-forming fluids by vapor-liquid inclusions in quartz and other minerals from ore zones of epithermal deposits. By studying fluid inclusions, we can determine the temperature, salinity, pressure and composition of mineralising fluids [5,6,7,8]. The development of Raman spectroscopy and its application to individual fluid inclusions has led to an increase in the number of papers on fluid composition [9,10,11,12,13]. This paper uses one of the complementary methods for solving complex problems of ore formation—the method of gas chromatography-mass spectrometry (GC-MS), which allows the detection of a wide range of organic compounds in ore-forming fluids [14]. The acquired data can be used to develop a genetic model of the deposits, which can be further applied to the prediction and exploration of new mineral deposits. Thus, the mineral resource base of precious metals could be expanded. The purpose of this paper is to summarise the geochemical and thermobarogeochemical characteristics of the epithermal Au-Ag deposits of the Central and East Kamchatka volcanogenic belts, to compare these characteristics among themselves and to identify the possible reasons for the difference between the deposits.
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Figure 1. The Kamchatka Peninsula, Russia, with the location of epithermal Au-Ag deposits in the contours of volcanogenic belts [15]. The deposits studied in this article are shown in bold.
Figure 1. The Kamchatka Peninsula, Russia, with the location of epithermal Au-Ag deposits in the contours of volcanogenic belts [15]. The deposits studied in this article are shown in bold.
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2. Geological and Mineralogical Background

Approximately 200 epithermal gold deposits and occurrences are known on the Kamchatka Peninsula [16], associated with modern subduction zones of the Asia-Pacific Rim. The deposits are confined to late Mesozoic and Cenozoic volcanogenic belts [17]: Eocene-Oligocene Koryak-Western belt consisting of volcanic rock (from basalt to rhyolite), Oligocene-Quaternary Central Kamchatka belt consisting of rhyolite-dacites, andesites and basalts and Pliocene-Quaternary Eastern Kamchatka belt consisting of basalts [18] (Figure 1).
Two types of mineral parageneses in ores of Au-Ag epithermal deposits, differing in the stability of mineral associations depending on the fugacity of sulfur (fS2), were distinguished [19,20]: low sulfidation (LS) and high sulfidation (HS); an intermediate type (IS) was added to the classification later [21]. This systematics of epithermal deposits is the most accepted in the international literature [22]. However, we adhered to the classification proposed earlier [23,24]—adularia-sericite deposits corresponding to the LS-type and acid-sulfate deposits (HS type), since it emphasizes the characteristics of mineral associations in ores and host rock metasomatites [25]. In this paper, we considered epithermal Au-Ag deposits located in the Central Kamchatka belt: Rodnikovoe, Baranyevskoe, Kumroch, Lazurnoe (Ad-Ser) and Maletoyvayam (Ac-Sul).
The studied epithermal deposits of Ad-Ser type in Kamchatka are hosted by basalts, basaltic andesite, andesite, its tuffs, gabbro-diorite, diorite and quartz diorite where Au-Ag mineralisation is associated with adular-quartz, carbonate-quartz and quartz veins. These deposits are accompanied mainly by sericite and quartz-sericite metasomatites and argillites. The Maletoyvayam Ac-Sul deposit is composed of andesites, tuffs and tuff sandstones. Vuggy silica is located in the central part of the deposit, while along the periphery, it is successively replaced by alunite-kaolin-quartz, sericite-kaolin-quartz and kaolinite-quartz metasomatitis; the outer parts of the deposit consist of argillicites and propylites [26]. More detailed data on the Au-Ag mineralisation of these deposits are given in [25].
The Rodnikovoe deposit is located in the southern part of the Central-Kamchatka volcanogenic belt (Figure 1) in the area of the Vilyuchinsk hot springs, where hydrothermal activity and associated ore mineralisation are manifested in the Mutnovsko-Asachinskaya geothermal zone [27,28,29]. It is represented by a stockwork of quartz-carbonate veins (Figure 2a,b) embedded in diorite and gabbro-diorite. The age of mineralisation of the veins, determined by the K-Ar method on adularia, is 0.7–2.8 Ma [28]; the age of quartz-carbonate veins is in the same range (0.9–1.1 Ma) [30]. Two ore-productive stages (gold-sulfide-quartz and gold-adularia-quartz) were identified [28]. In addition, two gold assemblages have been described in detail at the deposit [31]: silver-aguilariteacanthite assemblage containing Au-Ag alloys with 2–51 at. % Au and gold-uytenbogaardtite-acanthite assemblage with Au-Ag alloys of composition 43–89 at. % Au. Samples from gold-sulfide-quartz assemblage were examined.
The Baranyevskoe Au-Ag epithermal deposit is located in the central part of the Central-Kamchatka volcanogenic belt, in the Bystrinsky district of the Kamchatka. The Baranyevskoe deposit is one of the economically significant objects of the Balkhach gold ore cluster [32,33]. The age of the deposit, located in the late Miocene-Pliocene rocks, corresponds to the interval of 3.9–2.4 Ma by the K-Ar method on adularia [34,35]. The Baranyevskoe deposit is characterised by two Au-bearing assemblages [36]: an early gold-pyrite-quartz assemblage with low-grade native gold (52–74 at. % Au; 26–48 at. % Ag) in intergrowths with pyrite and a later gold-sulfosalt-quartz assemblage (Figure 2c,d) with high-grade (88–94 at. % Au) nugget gold in intergrowths with chalcopyrite [37]. Samples from an early gold-pyrite-quartz assemblage were examined.
The Lazurnoe ore occurrence is part of the Khim-Kirganik ore cluster located in the Bystrinsky district. This copper-polymetallic gold ore occurrence is part of the Kirganik ore field, which also includes the Kirganik and Sukhoe copper ore occurrences and the Lagernoe and Tumannoe copper-molybdenum ore occurrences. The ore field is located in the area of development of psammite tuffs of the Kirganik formation, which are crosscutted by Miocene diorites, quartz diorites of the Lavkin complex [38]. A series of ore-bearing quartz (Figure 2e,f) and quartz-carbonate veins with a length of 100–1400 m have been identified. In addition, gold mineralisation is found in a 100 m-length stockwork.
The Kumroch deposit is located in the northern part of the East-Kamchatka volcanogenic belt (Figure 1), in the Ust-Kamchatka region, in the upper reaches of the Bystraya River. It is believed that the epithermal gold-silver deposit is associated with a copper-porphyry system within a single ore field [39]. The epithermal deposit is associated with subvolcanic bodies of andesites, diorites and granodiorite-porphyries of the Miocene-Pliocene age. Ore paragenesis are represented by two assemblages: gold-polysulfide-quartz (galena and sphalerite) and gold-sulfide-quartz (pyrite and chalcopyrite), as well as intermediate varieties where the bands in adularia-quartz veins are composed of pyrite-chalcopyrite-galena-sphalerite aggregates (Figure 2g,h) and fahlores of the tennantite–tetrahedrite series. Samples from this assemblage were examined in this work. The Kumroch deposit is one of the promising ore objects of epithermal gold-silver mineralisation in Kamchatka [40].
The Maletoyvayam deposit is located in the northeast of the Central-Kamchatka volcanogenic belt and is confined to volcano-tectonic structures within the Vetrovayam volcanic zone (southwestern part of the Koryak Upland) (Figure 1) [26,41]. Among the studied deposits in this paper, only Maletoyvayam relates to Ac-Sul type deposits, and recently similar parageneses were described in the upper horizons of the site “BAM” in the Ozernovskoe deposit [42]. A combination of the Ad-Ser type with superimposed Ac-Sul type mineralisations also occurs in the Vilyuchinskoe ore occurrence [25]. Two mineral associations were identified during the study of quartz (Figure 2i,j) in the Maletoyvayam deposit: the earlier pyrite-quartz (295–245 °C) and the late Au-bearing maletoyvayamite-quartz associations/stages (255–245 °C) [36]. At the same time, the productive gold ore stage is characterised by two main ore assemblages: (1) gold-rich (without silver); and (2) silver-rich, crystallising from solutions of varying degrees of acidity [43]. The studied samples belong to the gold-rich assemblage.

3. Sampling and Analytical Methods

A collection of about 50 samples of quartz veins with ore mineralisation was selected by the authors during the 2019–2022 fieldwork on the Kamchatka: Rodnikovoe, Baranyevskoe, Lazurnoe and Kumroch deposits. Samples from the Maletoyvayam deposits were obtained from the research and production company “Eleechem” in 2016. About thirty samples from the quartz veins (Figure 2) of the all deposits were selected for geochemical and fluid inclusion studies. The most informative thin sections of rocks with large fluid inclusions (10–30 µm) were selected from the prepared ones. The 2–3 mm thin sections were analysed for each deposit. Most of the analyses (except for ICP-AES and fire-assay analysis) were carried out at the Analytical Center for multi-elemental and isotope research of the Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences (IGM SB RAS) in Novosibirsk, Russia.

3.1. Geochemistry of Rare Elements

Thirty-one samples were analysed for the content of rare elements (including chalcophile elements) by the combined method of ICP-AES + ICP-MS in the testing laboratory of JSC SGS Vostok Limited, Chita branch, Russia. All elements were analysed according to the company’s internal method (GE_ICM40Q12), including the decomposition of the samples in a mixture of acids. After decomposition, the solution was analysed using an Optima 8300 (Sheltec) inductively coupled plasma atomic emission spectrometer, an atomic absorption spectrometer AA240 (Agilent Technologies) and an inductively coupled plasma mass spectrometer NexION 300D (Perkin Elmer).
Analysis of Au was performed at the same laboratory from a 50 g sample by fire-assay analysis with inductively coupled plasma atomic emission spectroscopy (ICP-AES) ending. Fire-assay is a total-recovery method. The method includes the fusion of the samples at a 1100 °C temperature, throughout which gold is segregated from gangue and gathered within a molten Pb. Then, Pb is eliminated by cupellation, afresh at high temperature, to lead to a prill of Au. The prill is solved in acids. The highest-quality assay consumables (flux, crucibles and cupels) are sourced from around the world to ensure the assay integrity. Accreditation scope: Au, 0.005 ppm–10,000 ppm.

3.2. Fluid Inclusions Analysis

We used half of the sample to make double-polished thin sections for studying individual fluid inclusions (FIs). The second half was crushed and forced through a sieve. Pure quartz and calcite without visible impurities were picked over using a binocular magnifying glass. Microthermometric, Raman and GC–MS analyses were performed at the laboratory of Thermobarogeochemistry, IGM SB RAS, Russia.
Mircothermometric measurements were carried out in a TH–MSG–600 microthermometry chamber (Linkam, UK) with a measurement range from −196 to +600 °C. The standard instrumental measurement accuracy is ±0.1 °C in the negative and ±5 °C in the positive temperature range. Homogenization (Thom), ice melting (Tmelt) and eutectic (Teut) temperatures were observed. Salinity and fluid pressure were calculated using [44]. The salt composition of the aqueous phase was determined based on the measured Teut, which characterises the water–salt system [45].
The composition of individual fluid inclusions was analysed by Raman spectroscopy on a single–channel Horiba J.Y. LabRAM HR800 Raman spectrometer equipped with an argon laser with a 1.5 μm diameter and a 0.75 W power according to the methods described in [46].
The bulk composition of fluids in minerals was determined by pyrolysis-free coupled gas chromatography–mass spectrometry (GC–MS) on a Focus GS/DSQ II Series Single Quadrupole MS analyzer (Thermo Scientific, Austin, TX, USA). When preparing samples for analysis, no acids, solvents or organic substances were used which could distort the initial composition of the extracted fluid. The sample preparation procedure for analysis excluded its contact with any solvents and other possible contamination. The input of the mixture extracted from the sample during the shock crushing was carried out online in a He flow without concentration including cryofocus. Blank online analyses were carried out before and after the ‘‘working” analysis. The previous analysis made it possible to control the release of gases sorbed by the sample surface, including atmospheric components, and to record the system blank at the end of the process. The degree and completeness of hydrocarbon and polycyclic aromatic hydrocarbon elution from the analytical column during temperature programming in a chromatograph thermostat were determined using the results of subsequent analysis. If necessary, the analytical column was thermoconditioned to achieve the required blank. The collected spectra were interpreted using both the AMDIS 2.73 software and manually, with background correction against spectra from the NIST 2020 and Wiley Registry 12th Edition Mass Spectral libraries (NIST MS Search 2.4). Peak areas in chromatograms were determined using the ICIS algorithm Xcalibur (1.4SR1 Qual Browser). This method is suitable for the detection of trace volatile concentrations exceeding tens of femtograms. The relative concentrations (rel.%) of volatile components in the studied mixture were obtained by normalising the areas of individual chromatographic peaks to the total area of all peaks [47,48].

4. Results

4.1. Geochemistry of Ore-Forming Elements

The results of the ore-forming element analyses of the quartz veins of the Au-Ag epithermal deposits are presented in Table S1, and the arithmetic average values are presented in Table 1, where they were normalised to average values for the Upper Continental Crust (UCC) [49]. The moderate concentrations of Ag (average: 2–81 ppm) and Au (average: 0.3–13 ppm) were contained in ore quartz veins of all the deposits (Table 1). High concentrations (average) of Zn (206 and 1501 ppm), Pb (502 and 1250 ppm) and Cu (148 and 6231 ppm) in the Kumroch and Lazurnoe deposits correlated with the presence of polymetallic mineralisation and copper specialisation in these deposits. High concentrations of As (792 ppm), Sb (662 ppm), Se (937 ppm), Te (71 ppm), Bi (35 ppm) and Ba (1056 ppm) were found in the Malethoyvayam (Ac-Sul) deposit, which is consistent with the considerable mineral diversity (Au tellurides, Au selenides and barite) in this deposit [25]. These characteristics of the deposit are shown in Figure 3, where the concentrations were normalised to the UCC, are shown.
The Au enrichment coefficients varied from hundreds to thousands of times (Table 1; Figure 3). The maximum value of Au enrichment was characteristic of the ore quartz veins of the Rodnikovoe deposit (7029), where Au-Ag alloys predominated over sulfides and tellurides of Ag(Au) in ore assemblages [37]. The minimum values of Au enrichment coefficients were observed in the Kumroch (461) and Lazurnoe (154) deposits in which polymetallic mineralisation (galena and sphalerite) and chalcopyrite predominated, while Au-Ag alloys were of subordinate importance. Thus, the Kumroch and Lazurnoe deposits were enriched with Cu (6 and 249), Zn (3 and 21) and Pb (25 and 62). In contrast to the above-described deposits, the Maletoyvayam was characterised by high enrichment coefficients of chalcophile elements ranging from hundreds (As and Bi) to thousands (Sb, Te and Se). It was this deposit that had a wide variety of Au chalcogenides [25].
Some peculiarities in the distribution of elements in the ore quartz veins are shown in Figure 4 and Figure 5. All deposits showed a correlation between Au and Ag (except Lazurnoe), Te and Bi. The quartz veins of the Lazurnoe deposit accumulated more silver than gold and were characterised by the lowest Au/Ag ratio (<0.1), while the highest Au/Ag value (2.7) was noted in veins of the Baranyevskoe deposit (see Table 1).
Tellurium dominated bismuth (Te/Bi = 1.8–2.4) in almost all deposits, except for single samples in the Rodnikovoe and Lazurnoe deposits (Figure 4b). This is consistent with Te-bearing mineral assemblages in these deposits. A positive correlation between Zn+Pb and Ag was shown in the Kumroch and Lazurnoe deposits, as these epithermal deposits include polymetallic mineralisation while the other three deposits generally have low Zn and Pb contents. The ore quartz veins of the Maletoyvayam deposit showed a positive correlation of Te with Bi (Figure 4b), and positive correlations of Ag with Te, Bi, Sb and Se (Figure 5a,d) at high chalcogens contents (Te, Bi, Sb and Se). The Lazurnoe deposit also showed elevated contents of Te, Bi and Se.

4.2. Fluid Inclusion Types

To establish the PTX-conditions of deposits formation, fluid inclusions (FIs) in quartz were analysed. Two types of fluid inclusions were found and distinguished according to phases present at 25 °C: two-phase vapor-liquid and single-phase vapor (or liquid) FIs. Two-phase FIs predominated in the samples (Figure 6) in form of fluid inclusion assemblages (groups up to 10) [51] or single fluid inclusions. FIAs of single-phase fluid inclusions were extremely rare (a maximum of up to 10% of the total number). FIAs in quartz are usually located randomly throughout the entire volume of grains, usually not confined to healed cracks; some FIAs are oriented along grain boundaries. Thus, they were identified as primary and pseudosecondary according to the traditional classification of FIs [52]. The fluid inclusion size varied from 5–10 μm (Baranyevskoe, Rodnikovoe and Maletoyvayam) to 8–30 μm (Lazurnoe and Kumroch). The shape of fluid inclusions varied: oval and irregularly shaped inclusions predominated, and elongated vacuoles were also found.

4.3. Homogenization Temperatures, Salinity and Pressure of Fluid

A summary of microthermometric data is presented in Table 2 and Figure 7 and Figure 8. The homogenisation temperature of FIs from the Baranyevskoe deposit ranged from 210 to 308 °C with homogenization into the liquid phase. The ice melting temperature varied from −1 to −6 °C, which means that the fluid salinity was 0.5–1.7 wt %. (NaCl-eq.). The fluid pressure was 19–98 bar.
Fluid inclusions from the Rodnikovoe deposit homogenized to liquid at the temperatures of 160–265 °C, the salinity varied from 0.9 to 2.6 wt %. (NaCl-eq.), and the pressure was 6–50 bar.
The homogenization temperatures of FIs from the Lazurnoe deposit were 270–285 °C, with homogenization occurring to the liquid phase. The fluid salinity was 1–1.7 wt %. (NaCl-eq.), and the pressure was 54–85 bar. The composition of the aqueous phase corresponded to Na and K chlorides, which was indicated by the eutectic temperatures ranging from −22.5 to −21.7 °C.
In the Kumroch deposit, the homogenization temperatures of FIs ranged from 205 to 300 °C (to liquid), the salinity varied from 0.9 to 6.8, and the pressure was 17–85 bar. The composition of the aqueous phase corresponded to Mg and Na chlorides, as indicated by the eutectic temperatures.
Fluid inclusions from the Maletoyvayam deposit homogenized to liquid at the temperatures of 173–290 °C, the salinity varied from 1 to 5 wt %. (NaCl-eq.), and the pressure was 8–72 bar.

4.4. Composition of the Gaseous Phase of Fluid Inclusions

Composition of volatiles in fluids was analysed by Raman spectroscopy and gas chromatography-mass spectrometry (GC-MS). Raman spectroscopy detected carbon dioxide (Figure 8a) and H2O (Figure 8b) in individual fluid inclusions from the Lazurnoe deposit. Similar spectra were found in fluid inclusions in the Kumroch deposit, whereas on others deposits, only H2O spectra were obtained probably due to the low density of inclusions.
GC-MS data showed that there were between 155 and 210 different compounds in the fluid from Baranyevskoe, Rodnikovoe, Lazurnoe, Kumroch and Maletoyvayam deposits. It was revealed that the fluids mainly consisted of H2O (57.67–94.65 rel.%) and CO2 (3.5–14.75 rel.%). Moreover, a wide range of hydrocarbons and their derivatives, as well as nitrogenated and sulfonated compounds, were found in the composition of volatiles in the fluid (Figure 9 and Table 3 and Table S2–S6). The total content of these compounds in fluids varied from 0.91 rel.% in the Rodnikovoe deposit to 31.4 rel.% in the Maletoyvayam deposit.
The share of alkanes ranged from 0.15 to 6.33 rel.%. This group was represented by a homologous series from methane (CH4) to heptadecane (C17H36). The contents of homologues of alkanes C1-C9, C10-C14 and C15-C17 varied within the ranges of 0.09–2.79, 0.02–3.34 and 0.03–2.18 rel.%, respectively (Table 3; Figure 9). The content of alkenes (C2H2–C17H34) was 0.07–2.01 rel.%. The group of cyclic hydrocarbons (C5H10–C15H24) was represented by cycloalkanes, cycloalkenes, arenes and polycyclic aromatic hydrocarbons (PAH); their contents varied from 0.18 to 2.97 rel.%.
Alcohols (CH4O–C8H10O3), ethers and esters (C5H8O–C14H26O2), aldehydes (CH2O–C18H36O), ketones (C3H6O–C15H30O) and carboxylic acids (CH2O2–C14H28O2) were oxygenated hydrocarbons identified in the fluids. There were 0.03–2.97 rel.% alcohols, <0.01–5.32 rel.% ethers and esters, 0.10–5.07 rel.% aldehydes, 0.05–2.48 rel.% ketones and 0.17–1 rel.% carboxylic acids in the mineralising fluids.
Heterocyclic compounds (C4H4O–C11H18O) were presented by dioxanes and furans, and their share ranged from <0.01 to 0.05 rel.%. As for nitrogenated compounds, molecular nitrogen (N2), ammonia (NH3) and nitriles (CHNO–C10H21NO) were found in the fluids. Their contents varied from 0.10 to 11.17 rel.%. The share of sulfonated compounds including H2S, SO2, CS2, COS and thiophenes (C4H4S-C12H20S) was 0.03–0.92 rel.%. The CO2/(CO2+H2O) ratio of mineralising fluids varied from 0.04 to 0.17.

5. Discussion

5.1. Geochemistry of Ore-Forming Elements

The Ac-Sul type Maletoyvayam deposit was extremely different from other Ad-Ser type deposits in its geochemical characteristics. The ore quartz veins of the Maletoyvayam deposit were characterised by high contents of As, Sb, Se, Te and Bi (Table 1; Figure 5). As shown in Figure 3, the deposit was 100–1000 times enriched in these elements relative to the Upper Continental Crust, probably indicating the geochemical affinity of a number of chalcophile elements and their synchronous involvement in ore-forming fluids. This has led to a mineral diversity in this deposit, where both typical and rare minerals of epithermal deposits are present: enargite-famatinite solid solution (Cu3AsS4–Cu3SbS4), senarmontite (Sb2O3), tripuhyite (FeSbO4), bismite (Bi2O3), roosveltite (BiAsO4), tiemannite (HgSe), antimonselite (Sb2Se3) and Sb-bearing antimonselite (Bi,Sb)2Se3), Te-Se solid solutions and barite [25]. The new minerals have been recognised in the Maletoyvayam deposit in recent years, which are the main gold concentrators: maletoyvayamite–tolstykhite solid solutions (Au3Se4Te6–Au3S4Te6), gachingite (Au (Te1−xSex)0.2≈x≤0.5) and auroselenide (AuSe) [53].
Among the Ad-Ser type deposits, Kumroch and Lazurnoe differed from Rodnikovoe and Baranyevskoe by high contents of Zn, Pb and Cu (Table 1; Figure 3 and Figure 4c) which is due to the presence of polymetallic mineralisation (sphalerite and galena) in the rocks of these deposits. They belong to the gold-telluride metallogenic type [25] with a large contribution of polymetallic (Pb and Zn) association, as well as the Amethistovoe and Vilyuchenskoe deposits in Kamchatka [54,55]. The Kumroch deposit is considered to represent a single system combining both Ad-Ser type epithermal gold-silver and copper porphyry mineralisation [39]. The same is true for the Lazurnoe deposit.
The enrichment by Au and Ag of ore quartz veins of the Lazurnoe deposit normalized to the UCC (Figure 3) differed from other studied deposits: Ag dominated over Au in its ores (Figure 4a). The ore quartz veins of the Lazurnoe deposit were characterised by the lowest Au/Ag ratio (0.048–0.001), indicating the predominance of silver mineralisation in this deposit. Similar deposits occurred in the Chukotka (Russia): Kupol and Dvoynoe deposits [56]. The Co/Ni value (Table 1) in quartz veins of the studied epithermal deposits was <1.0 (0.11–0.60), which is typical for medium and low-temperature hydrothermal fluids of meteoric origin [57], and was consistent with the obtained data (160–308 °C; see Table 2). The same low Co/Ni ratios are characteristic of the deposits of the Chukotka (Valunistoe, Dvoynoe and Kupol) and Magadan District (Kubaka, Birkachan, Burgali, Magnitnoye and Olcha) [56,58,59,60]. The elevated Co/Ni ratio (1.15) in quartz veins of the Kumroch deposit probably indicated the superposition of late magmatic Co-bearing fluid on early epithermal mineralisation.

5.2. Conditions of Au-Ag Mineralisation Formation

According to the results of studying fluid inclusions, the deposits were formed at temperatures of 160–308 °C by aqueous fluids with the salinity of 0.5–6.8 wt. % (NaCl-eq.) (Table 2; Figure 10). The Kumroch and Maletoyvayam deposits were formed in a wide range of temperatures and salinities (205–300 °C, 0.9–6.8 wt. % (NaCl-eq.) and 173–290 °C, 1–5 wt. % (NaCl-eq.), respectively). The Baranyevskoe and Rodnikovoe had moderate ranges of salinity (0.5–1.7 and 0.9–2.6 wt. % (NaCl-eq.), respectively) with wide temperature ranges (210–308 and 160–265 °C, respectively). The narrowest temperature-salinity intervals of formation were determined for the Lazurnoe deposits. Temperature and salinity parameters of ore-forming fluids are generally medium temperature with low-moderate salinity.
Similar temperature conditions were established for other epithermal gold-silver deposits of Kamchatka. For example, the Asachinskoe deposit was formed at temperatures of 160–250 °C with salinities of 1–5.2 wt. % (NaCl-eq.) [61,62]. The Vilyuchinskoe ore occurrence was formed at temperatures of 210–270 °C with a fluid salinity range of 0.5–0.7 wt. % (NaCl-eq.) [55]. Moreover, our data on formation conditions of the Maletoyvayam, Kumroch and Rodnikovoe are consistent with those previously obtained by [36,40,63]. It should be noted that fluid characteristics of Kamchatka deposits were close to that of epithermal Au–Ag–Se–Te deposits of the Chukchi Peninsula (low and moderate temperatures of fluids, low fluid salinity and domination of carbon dioxide among volatiles) [64].
Major volatile components in the mineralizing fluids of the deposits were H2O and CO2, while other compounds (hydrocarbons, nitrogenated and sulfonated) were in subordinate amounts. It should be noted that fluids of the Maletoyvayam deposit contained elevated concentrations of hydrocarbons, nitrogenated and sulfonated compounds (31.4 rel.% in total). Next in terms of such compounds content was the Lazurnoe deposits (12.71 rel.%). While the Baranyevskoe, Rodnikovoe and Kumroch contained only 3.77, 0.91 and 5.26 rel.% of HC, N- and S-compounds, respectively, Volatile compounds actively participate in the process of ore deposits formation. Organic compounds found in fluid inclusions may take part in the concentration and mobilisation of ore elements [65,66]. It was experimentally shown that hydrocarbons could be formed at subduction zone conditions [67]. They then become part of the fluids circulating in the Earth’s crust. Water-soluble organic compounds are capable of forming organometallic complexes in which gold and silver are transported in solutions [68,69]. When the PT conditions change, organometallic compounds disintegrate and crystallisation of gold and silver occurs. Carbon dioxide provides the buffer capacity of the fluid to maintain high solubility of metals [70]. Sulfonated compounds found in ore-forming fluids also have a beneficial effect on the solubility of gold complexes [71]. Nitrogenated compounds can form stable organometallic compounds for metal transport [72]. According to the GC-MS data, ore-forming fluids had water-carbon dioxide composition with an admixture of hydrocarbons, nitrogenated and sulfonated compounds (up to 31.4 rel.%). Fluid composition diversity and the presence of various volatiles contributed to the formation of ore deposits.
The parameters of mineral-forming solutions of all studied deposits were similar. They are characterised by medium temperatures of formation and low-medium salinity of solutions, as well as low fluid pressure. All deposits were characterised by the predominance of water and carbon dioxide in the fluid. Only the increased content of organic compounds (31.4 rel.%) was distinguished by the Maletoyvayam deposit. It is worth noting that the content of selenium and tellurium in the ores of the Maletoyvayam deposit was also increased. The extremely increased content of nitrogenated compounds (11.17 rel.%) in the Maletoyvayam deposit fluid was also striking. This gives us a reason to assume that organic compounds favourably affected the concentrations of these elements in the mineralising fluid.

5.3. Origin of Hydrocarbons

Two mechanisms are responsible for the formation of hydrocarbons in solutions: biogenic by algae or bacteria or abiogenic by chemical reactions at high temperatures and pressures (thermogenic). Different criteria are used to identify these mechanisms. For example, C7-C21 alkanes, alcohols, ketones, carboxylic acids and aldehydes can be formed by living organisms [73,74]. The inorganic-thermogenic source is indicated by low-molecular-weight n-C10-C14 alkanes [75].
In the Lazurnoe and Maletoyvayam deposits, which had a high hydrocarbon content, aliphatic hydrocarbons (alkanes) and oxygenated hydrocarbons (ethers, esters, aldehydes and ketones) predominated (Figure 9), which suggests a significant biogenic contribution of hydrocarbons to the transport of ore components. Among the detected alkanes, the low-molecular-weight homologues of the n-C1-C17 composition were predominant (Table 3). Bacteria synthesised low-molecular-weight odd homologues of n-C7, n-C9, n-C11, n-C13 and n-C15. Short-chain hydrocarbons (n-C10-C14), which predominated in the Maletoyvayam deposit, were not synthesized at all by hydrothermal biota [76]. It is likely that some part of the organic compounds is a product of the thermocatalytic transformation of organic residues formed as a result of processes occurring in the water (vapor)-rock system (possibly with the participation of volatile components of the magma). This is indirectly confirmed by the fact that carboxylic acids (synthesised by bacteria) and other obviously biogenic components—steroids, esters and terpenes—are almost absent in the studied inclusions [77]. The Lazurnoe deposit is characterised by the presence of esters and n-C15-C17 alkanes in the fluid, so biogenic hydrocarbon formation can be assumed for it to a greater extent, whereas for the Kumroch deposit the amount of n-C15-C17 alkanes was significantly lower (Figure 9).
The composition of organic compounds in hydrothermal systems of the Far East has both biogenic and (less frequently) abiogenic origins [75]. Thus, the results of our studies of epithermal Au-Ag deposits of Kamchatka showed that C7-C17 alkanes, esters, ketones, carboxylic acids and aldehydes are indicators of biogenic origin of organic compounds, while C10-C14 alkanes may be the result of thermogenic origin.

5.4. The Role of Organic Compounds in the Accumulation of Ore-Forming Elements

As shown by the results of the studies, organic compounds were present in the ore-forming solutions of all five deposits (Table 3), which means that they actively participated in the transfer of Au and other ore components in the form of organometallic compounds. Hydrocarbons are able to accumulate and transport a significant amount of Ag, Au and the other native elements [78]. Nitrogen and sulfur are involved in complexation, forming compounds: Au(CN)2−, Au(SCN)−, Au(S2O3)−3, Au(HS2)−, etc. [79], which are decay products of algae [68]. N-compounds were characteristic only of the Maletoyvayam deposit (11 rel.%) (Table 3; Figure 9). They probably played an essential role in gold transport and formation of mineral parageneses of this deposit. In the acidic environment of boiling hydrothermal fluids, cyanide ions are oxidized to CO2 and free nitrogen to form pyrite: Fe(CN) + 3HS− + 16H2O = FeS2 + SO + 6CO2 + 3N2 + 35H+ + 40e− [80], which favours sulfidation of sediments. This mechanism could be realised in the Maletoyvayam deposit, since molecular nitrogen and CO2 are found in the composition of its fluids, and pyrite is the main mineral of the earliest association [81].
According to the results of the fluid inclusion study, the studied deposits were formed at temperatures of 160–308 °C (Figure 10). Gold can be dissolved as Au(HS)2 complexes [82] or selenocysteine (HSeCH2-CHNH2-COOH) [83] at temperatures around 200 °C in near-neutral or weakly alkaline solutions of Ad-Ser type deposits.
Selenium is one of the leading elements in the ores of the studied deposits (Figure 3), and therefore a significant component of hydrothermal solutions. Se-ligand-organic complexes are transported by ascending hydrothermal fluids, decompose and release selenium, which then participates in the formation of inorganic compounds (selenites, selenates and selenides), releasing hydrocarbons. The presence of organic compounds in fluid inclusions implies a role in the concentration and mobilisation of ore elements, including selenium [14]. Selenium is a good ligand for silver and probably other ore elements, since Se is usually positively correlated with noble metals and chalcogens. However, it is worth noting that the contribution of selenium to the accumulation of metals in ore-forming events increases with decreasing temperature [84]. The reduced homogenisation temperatures for quartz from the Maletoyvayam and Rodnikovoe deposits (Figure 10) are consistent with the fact that Se plays a significant role in the formation of mineral parageneses in exactly these deposits [81].
It is known [85] that Se can form organic selenium compounds in solutions: Se–H, O–Se–C, O–Se–O, Se–C and also Se–N. At the same time, Se is positively correlated with As, Ba, Sb, Ag and Au, indicating their joint mechanism of ore formation.
According to [14], the primary source of organic compounds and selenium are bacteria and/or algae, which contribute to the enrichment of intermediate collectors with selenium. The high Se contents were noted in the Lazurnoe and Maletoyvayam deposits (Table 1; Figure 4c), which contained the large amounts of hydrocarbons in the inclusions (Table 3; Figure 9). This supports the idea that selenium is involved in the formation of inorganic compounds that release hydrocarbons [14]. Fluids from the Lazurnoe, Kumroch and Maletoyvayam deposits contained significant concentrations of sulfonated compounds (1% or more), unlike other deposits. Sulfonated compounds are commonly a part of the ore-forming systems of various deposits. It should be noted that their elevated content is attributed to the “productive” stages of ore formation when sulfides crystallize [86,87].
In hydrothermal solutions with a low fSe2/fS2 ratio of < 1, with fO2 below the magnetite-hematite (MH) buffer, selenium is incorporated into other mineral species as a solid solution by sulfur substitution [88], as in the Rodnikovoe deposit (acanthite solid solution; Se-containing sulfosalts) [31]. An increase in these ratios is only allowed at high pH and fO2, which leads to the change of Au–S complexes by Au–S–Se and Au–Se minerals [89]. The formation of the majority of selenide requires oxidising conditions and acidic environments [90,91]. Such conditions are realised in the Maletoyvayam deposit, where an auroselenide (AuSe) is discovered [53].

6. Conclusions

In this research, we demonstrated that all studied deposits were formed at similar parameters: medium temperatures (160–308 °C), low-medium salinity of solutions (0.5–6.8 wt. % NaCl-eq.) and low fluid pressure (6–98 bar). The mineralising fluids were dominated by water and carbon dioxide. Fluids from all deposits contained various organic compounds, and the total number of compounds reached 210.
The high content of organic compounds (31.4 rel.%) was distinguished in the Maletoyvayam deposit only. It is worth noting that the contents of ore elements (Se, Te, Bi, Sb and As) in the ore quartz veins of the Maletoyvayam deposit were also higher compared with those of the deposits of Ad-Ser type. Apparently, the organic compounds favourably affected the concentrations of these elements in the mineralising fluid. Low-molecular-weight n-C10-C14 alkanes of the Maletoyvayam deposit indicated mainly thermogenic origin of hydrocarbons.
Among the Ad-Ser type deposits, Kumroch and Lazurnoe differed from Rodnikovoe and Baranyevskoe by high contents of Zn, Pb and Cu and high contents of ethers and esters. The presence of esters (Kumroch and Lazurnoe) and n-C15-C17 alkanes (Lazurnoe) in the fluid indicated biogenic hydrocarbon formation.
The alkanes, alkenes, ethers, ketones, carboxylic acids and aldehydes detected in epithermal Au-Ag deposits of Kamchatka were indicative of both biogenic and thermogenic origin of organic compounds.
The contents of ore-forming elements in the ores were consistent with the features of mineral assemblages: polymetallic (Pb, Zn and Cu) in the Kumroch and Lazurnoe deposits and Au-seleno-telluride with sulfosalts (Au, Se, Te, Sb and As) at Maletoyvayam.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/min15010002/s1. Table S1: Average concentrations of rare elements (ppm) in quartz veins of the Au–Ag epithermal deposits of the Kamchatka and their contents normalised to the UCC; Table S2: Results of GC–MS analysis of volatiles extracted by mechanical shock destruction from quartz of the Baranyevskoe deposit; Table S3: Results of GC–MS analysis of volatiles extracted by mechanical shock destruction from quartz of the Rodnikovoe deposit; Table S4: Results of GC–MS analysis of volatiles extracted by mechanical shock destruction from quartz of the Lazurnoe deposit; Table S5: Results of GC–MS analysis of volatiles extracted by mechanical shock destruction from quartz of the Kumroch deposit; Table S6: Results of GC–MS analysis of volatiles extracted by mechanical shock destruction from quartz of the Maletoyvayam deposit.

Author Contributions

Conceptualisation, N.T.; investigation, M.S. and E.S.; visualisation, M.S. and E.S.; writing—original draft, M.S. and E.S.; writing—review and editing, N.T. All authors have read and agreed to the published version of the manuscript.

Funding

The reported study was funded by Russian Science Foundation (№ 23-27-00258) https://rscf.ru/en/project/23-27-00258/ (accessed on 22 December 2024).

Data Availability Statement

Data are contained within the article and Supplementary Materials.

Acknowledgments

We sincerely thank two anonymous reviewers whose valuable comments helped improve the article. We are grateful to N. Belkina for technical assistance in preparing the manuscript.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Figure 2. Photos of representative samples from epithermal Au-Ag deposits of the Kamchatka: (a) colloform-crustiform banding quartz-adularia vein hosting the Au-Ag mineralisation from the Rodnikovoe deposit; (b) microphotography of gold-sulfosalt-sulfide paragenesis in quartz; (c,d) sample of sericite-adularia-quartz composition with crustified-breccia texture containing disseminated sulfide, sulfosalts and visible gold from the Baranyevskoe deposit; (e,f) sample of an adular-quartz vein with polysulfide nests and veins from the Lazurnoe deposit; (g,h) metasomatite over siltstone with breccia texture containing disseminated sulfides in quartz from the Kumroch deposit; (i) fragment of the quartz vein with veins and nests of enargite from Maletoyvayam deposit; (j) BSE-image. Intergrowth of maletoyvayamite with enargite in quartz. Cp—chalcopyrite; Gl—galena; Sp—sphalerite; Bn—bornite; Py—pyrite; Wa—watanabeite; Eng—enargite; Mty—maletoyvayamite; Qz—quartz.
Figure 2. Photos of representative samples from epithermal Au-Ag deposits of the Kamchatka: (a) colloform-crustiform banding quartz-adularia vein hosting the Au-Ag mineralisation from the Rodnikovoe deposit; (b) microphotography of gold-sulfosalt-sulfide paragenesis in quartz; (c,d) sample of sericite-adularia-quartz composition with crustified-breccia texture containing disseminated sulfide, sulfosalts and visible gold from the Baranyevskoe deposit; (e,f) sample of an adular-quartz vein with polysulfide nests and veins from the Lazurnoe deposit; (g,h) metasomatite over siltstone with breccia texture containing disseminated sulfides in quartz from the Kumroch deposit; (i) fragment of the quartz vein with veins and nests of enargite from Maletoyvayam deposit; (j) BSE-image. Intergrowth of maletoyvayamite with enargite in quartz. Cp—chalcopyrite; Gl—galena; Sp—sphalerite; Bn—bornite; Py—pyrite; Wa—watanabeite; Eng—enargite; Mty—maletoyvayamite; Qz—quartz.
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Figure 3. Distribution of ore-forming elements in quartz veins of the Au-Ag epithermal deposits of the Kamchatka, normalised to the average values for the UCC (enrichment coefficients) [49].
Figure 3. Distribution of ore-forming elements in quartz veins of the Au-Ag epithermal deposits of the Kamchatka, normalised to the average values for the UCC (enrichment coefficients) [49].
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Figure 4. The concentration relationships of Au vs. Ag (a), Bi vs. Te (b), Se vs. Te (c) and Ag vs. Pb+Zn (d) from quartz veins of the Au–Ag epithermal deposits of the Kamchatka based on ICP-OES analyses.
Figure 4. The concentration relationships of Au vs. Ag (a), Bi vs. Te (b), Se vs. Te (c) and Ag vs. Pb+Zn (d) from quartz veins of the Au–Ag epithermal deposits of the Kamchatka based on ICP-OES analyses.
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Figure 5. The concentration relationships of Ag with Te (a), Bi (b), Sb (c) and Se (d) from quartz veins of the Au–Ag epithermal deposits of the Kamchatka based on ICP-OES analyses.
Figure 5. The concentration relationships of Ag with Te (a), Bi (b), Sb (c) and Se (d) from quartz veins of the Au–Ag epithermal deposits of the Kamchatka based on ICP-OES analyses.
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Figure 6. FlAs of two-phase fluid inclusions in quartz from Baranyevskoe (a), Rodnikovoe (b), Maletoyvayam (c), Lazurnoe (d) and Kumroch (e) deposits and single-phase FIAs from the Kumroch deposit (f), typical for these deposits.
Figure 6. FlAs of two-phase fluid inclusions in quartz from Baranyevskoe (a), Rodnikovoe (b), Maletoyvayam (c), Lazurnoe (d) and Kumroch (e) deposits and single-phase FIAs from the Kumroch deposit (f), typical for these deposits.
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Figure 7. Homogenization temperature frequency distribution diagram for the epithermal Au-Ag deposits in Kamchatka.
Figure 7. Homogenization temperature frequency distribution diagram for the epithermal Au-Ag deposits in Kamchatka.
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Figure 8. Raman spectra of CO2 (a) and H2O (b) in two-phase vapor-liquid fluid inclusions from the Lazurnoe deposit.
Figure 8. Raman spectra of CO2 (a) and H2O (b) in two-phase vapor-liquid fluid inclusions from the Lazurnoe deposit.
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Figure 9. Compositions of volatiles (rel.%) and organic compounds extracted from fluid inclusions in quartz of the studied deposits according to the GC-MS data.
Figure 9. Compositions of volatiles (rel.%) and organic compounds extracted from fluid inclusions in quartz of the studied deposits according to the GC-MS data.
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Figure 10. Homogenization temperature–salinity ranges of mineralising fluids of the deposits.
Figure 10. Homogenization temperature–salinity ranges of mineralising fluids of the deposits.
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Table 1. Average concentrations of ore-forming elements (ppm) in quartz veins of the Au–Ag epithermal deposits of the Kamchatka and their contents normalised to the UCC [49].
Table 1. Average concentrations of ore-forming elements (ppm) in quartz veins of the Au–Ag epithermal deposits of the Kamchatka and their contents normalised to the UCC [49].
DepositRodnikovoeBaranyevskoeKumrochLazurnoeMaletoyvayam
Avg. Value
N = 4		Sam./
UCC		Avg. Value
N = 9		Sam./
UCC		Avg. Value
N = 8		Sam./
UCC		Avg. Value
N = 4		Sam./
UCC		Avg. Value
N = 6		Sam./
UCC
Co2.000.206.170.625.130.516.550.662.700.27
Ni17.600.8816.740.844.480.2210.930.559.250.46
Zn13.750.1962.330.882062.90150121.1319.580.28
As43.5029.0044.4429.6316611115.0010.00792528
Se11.352272.0040.002.4348.5846.8593754.081082
Ag80.9016182.5651.242.3246.3546.5393110.67213
Sb44.2322115.0074.9960.673039.2346.136623312
Te0.082.960.4516.830.6323.443.7013770.902626
Ba66.250.121210.226541.193120.5710561.92
Pb4.530.2336.841.8450225.10125062.4858.422.92
Bi3.5427.870.262.030.262.0814.5011434.98275
Cu39.231.5754.812.191485.90623124931412.56
Au12.6570296.9238460.834610.281544.362423
Au/Ag0.16 2.70 0.36 0.01 0.41
Te/Bi0.02 1.76 2.40 0.26 2.03
Co/Ni0.11 0.37 1.15 0.60 0.29
Note: the concentration of rare elements of each sample is presented (Table S1). The table presents arithmetic mean concentrations of ore-forming elements. The average Te content for the UCC is taken from [50].
Table 2. Results of microthermometric studies of two-phase fluid inclusions in the studied deposits.
Table 2. Results of microthermometric studies of two-phase fluid inclusions in the studied deposits.
DepositFIA
Type		NThom, °CTmelt, °CTeut, °CSalinity, wt. % (NaCl-eq.)Pressure, Bar
RodnikovoeP,PS28 160 – 265 226 −1.5…−0.5-0.9–2.66–50
BaranyevskoeP,PS31 210 – 308 268 −1…−0.6-0.5–1.719–98
LazurnoeP58 270 – 285 281 −1…−0.6−22.5…−21.71–1.754–85
KumrochP,PS63 205 – 300 274 −4.2…−0.5−32…−29.50.9–6.817–85
MaletoyvayamP,PS30 173 – 290 252 −3…−0.6-1–58–72
Note: FIA types: P—primary; PS—pseudosecondary; N—number of analysed fluid inclusions; Thom—range of homogenization temperatures/mean values; Tmelt—ice-melting temperature; Teut—eutectic temperature.
Table 3. Compositions (rel.%) and quantities (in brackets) of volatile components released during a single impact distraction of fluid inclusions in minerals from the studied deposits (GC-MS data).
Table 3. Compositions (rel.%) and quantities (in brackets) of volatile components released during a single impact distraction of fluid inclusions in minerals from the studied deposits (GC-MS data).
ComponentsMW *BaranyevskoeRodnikovoeLazurnoeKumrochMaletoyvayam
Aliphatic hydrocarbons
Paraffins (alkanes)
(CH4–C17H36)		16–2402.33 (18)0.19 (17)2.34 (20)0.15 (19)6.33 (40)
C1-C92.260.150.130.092.79
C10-C140.030.020.050.033.34
C15-C170.050.032.180.040.20
Olefins (alkenes) (C2H2–C17H34)26–2380.07 (20)0.12 (24)0.42 (29)0.25 (28)2.01 (31)
Cyclic hydrocarbons
Cycloalkanes, cycloalkenes, arenes, PAH
(C5H10–C15H24)		70–2040.19 (18)0.90 (23)0.23 (17)0.18 (17)2.97 (24)
Oxygenated hydrocarbons
Alcohols (CH4O–C8H10O3)32–1540.15 (9)0.03 (4)0.26 (15)0.20 (13)0.28 (7)
Ethers and esters (C5H8O–C14H26O2)84–2260.23 (12)<0.01 (6)5.32 (13)1.93 (14)0.13 (3)
Aldehydes
(CH2O–C18H36O)		30–2680.24 (22)0.10 (18)0.48 (28)0.49 (27)4.31 (23)
Ketones
(C3H6O–C15H30O)		58–2260.15 (17)0.05 (12)0.79 (22)0.15 (21)2.48 (13)
Carboxylic acids (CH2O2–C14H28O2)46–2280.19 (14)0.17 (15)1.00 (16)0.32 (13)0.77 (13)
Heterocyclic compounds
Dioxanes, furans (C4H4O–C11H18O)68–1660.01 (7)<0.01 (8)0.02 (9)0.01 (10)0.05 (9)
Nitrogenated compounds
N2, ammonia, nitriles
(N2–C10H21NO)		17–1710.14 (12)0.14 (12)0.57 (23)0.58 (21)11.17 (14)
Sulfonated compounds
H2S, SO2, CS2, COS, thiophenes (H2S–C12H20S)34–1960.08 (15)0.03 (13)1.28 (15)1.00 (15)0.92 (12)
Inorganic compounds
CO2446.604.4414.753.5010.93
H2O1889.6394.6572.5491.2557.67
Ar400.02-0.0010.001-
Number of components167155210201192
CO2/(CO2+H2O)0.040.040.170.040.16
* MW—nominal mass.
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Shapovalova, M.; Shaparenko, E.; Tolstykh, N. Geochemistry and Fluid Inclusion of Epithermal Gold-Silver Deposits in Kamchatka, Russia. Minerals 2025, 15, 2. https://doi.org/10.3390/min15010002

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Shapovalova M, Shaparenko E, Tolstykh N. Geochemistry and Fluid Inclusion of Epithermal Gold-Silver Deposits in Kamchatka, Russia. Minerals. 2025; 15(1):2. https://doi.org/10.3390/min15010002

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Shapovalova, Maria, Elena Shaparenko, and Nadezhda Tolstykh. 2025. "Geochemistry and Fluid Inclusion of Epithermal Gold-Silver Deposits in Kamchatka, Russia" Minerals 15, no. 1: 2. https://doi.org/10.3390/min15010002

APA Style

Shapovalova, M., Shaparenko, E., & Tolstykh, N. (2025). Geochemistry and Fluid Inclusion of Epithermal Gold-Silver Deposits in Kamchatka, Russia. Minerals, 15(1), 2. https://doi.org/10.3390/min15010002

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