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An original database compiled by the authors on volatile components of mineral-hosted fluid inclusions currently includes 12 470 analyses from 480 publications and was used to calculate the average gas phase composition of fluids that formed hydrothermal deposits throughout the Earth's geological evolution, from the Archean to Cenozoic. The paper reviews the methods used in the study, their potential errors, and limitations. Characteristics of the gas composition of fluids are traced for more than 300 ore deposits of Au, Sn, W, Cu, Cu, Pb, Zn, Sb, Mo, and U. The dominant volatile component of natural mineralizing fluids in the Earth's crust is carbon dioxide, regardless of the geologic age. The fluids contain subordinate amounts of reduced carbon species (methane) and nitrogen, as well as minor amounts of hydrogen sulfide and some other gases. The Cenozoic fluids commonly contain more nitrogen than methane. These relations are occasionally also found in the Precambrian fluids. The CO2/CH4 ratio as an indicator of the redox state of the system notably increased over the Earth's geological history. [ABSTRACT FROM AUTHOR]

The paper presents data on quartz-hosted fluid inclusions in commercial ores of various type (veinlet−disseminated and vein) of the Verninskoe gold deposit. The ores of various types were found out to significantly vary in the values of some of their physicochemical parameters of the fluids and in the composition of these fluids. The fluids that formed the gold veins have a somewhat higher initial temperature (356–246°C), a higher density of carbon dioxide in gas inclusions (1.00–0.84 g/cm3), and a higher fluid pressure (3170–1390 bar) than those of the fluids that formed the veinlet–disseminated ores (330–252°C, 0.87–0.54 g/cm3, and 1960–570 bar, respectively). The fluids that formed the gold veins were enriched in CО2, Sr, Ag, Ga, Ge, Mn, Fe, Ni, Sn, Ba, and REE, whereas the fluids that formed veinlet–disseminated mineralization were richer in , Br, Sb, V, and Au. This situations may be explained by the interaction of the deep fluid with the terrigenous host rocks in the course of ore deposition. When vein quartz crystallized in relatively wide fractures, the fluid interacted with host rocks and changed not as much as when the veinlet−disseminated ores were formed in narrow fractures. The initial parameters of the fluid that formed the vein quartz were thus the closest to the characteristics of the fluid that transported the ore components, and the comparison of these data with the parameters of the fluids that formed the veinlet–disseminated mineralization demonstrates that they changed in the course of ore deposition. The mineral-forming fluids likely came from a deep-sitting source, and the mineral-forming processes may have involve granitoid-derived fluids. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of carbonate and sulfate–carbonate–clayey rocks of the Lower Maeotian in the sections of the bays of Cape Kazantip using a complex of analytical methods. It is established that the greatest variation of chemical, bituminological, phase, and carbon-isotope composition is characterized by carbonate–clay and clayey rocks of the section bottom. It is proved that the initial OM was accumulated mainly under reducing conditions, but has some variations in composition; it is characterized by a low degree of its catagenetic transformation, which indicates the preservation of the primary isotopic composition. The diverse phase composition of the clay fraction is revealed: dioctahedral illite, kaolinite, chlorite, glauconite, and weakly ordered mixed-layer formations of illite/smectite type with different ratios of illite and smectite components and varying degrees of ordering. Modeling of their diffraction profiles showed that the illite/smectite structure may indicate significant depths of sediment mobilization by mud volcanoes. The isotopic composition of the 13Сorg ranges widely from –33.72 to –19.27‰ the mode being –22.1...–24.93‰. The isotopic composition of 13Сorg below –25.6‰ may be related to the entry of isotope-light mass of methane-oxidizing bacteria into the OM. It was revealed that variations of isotopic composition curves 13Сcarb and 13Сorg along the section of the studied rocks are rarely characterized by unidirectional (positive or negative) variations and have different trends along the section. Direction of the 13Сcarb isotope composition curve with some variations has a pronounced upward trend toward heavier weighting, whereas the isotopic values of the 13Сorg reveals reverse tendency. The results obtained prove that the revealed variations in the composition of OM and carbon isotope composition in the Lower Maeotian sections of Cape Kazantip reflect variations in the sedimentation conditions of temperature, salinity, freshwater ingression, bioproductivity fluctuations, and the influence of local gas–fluid deposition. It is proposed to use such accessory minerals as zircon, monazite, and ilmenite as an indicator of mud paleovolcanism. [ABSTRACT FROM AUTHOR]

The Fernando de Noronha archipelago (southwest Atlantic, 345 km from the coast of Brazil) is considered as the result of mantle plume activity. However, data on the isotopic composition of helium and neon, which are, perhaps, the only unambiguous geochemical criterion for deep mantle plumes have not been published yet for the region. In this paper, we present the first data on the isotopic composition of helium, neon, argon, and nitrogen, obtained by stepwise crushing of mantle xenoliths from the basanites of the San José Formation. The results obtained may indicate that fluid inclusions contain the very first portions of the exsolved gases—they are ultra-depleted in helium in relation to neon and especially argon. This conclusion is also supported by He–Ar–CO2 systematics. The isotopic composition of helium (4He/3He = 31 879 ± 6796) and neon (21Ne/22Ne(mantle) = 0.0453 ± 0.0012) indicates that it was indeed a mantle plume, identical in noble gas composition to the Kerguelen plume. According to the Ar–Ne isotope systematics 40Ar/36Ar (mantle) = 7455 ± 2290. Nitrogen is characterized by a heavy isotopic composition (δ15N = +5.4 ± 0.2‰), which corresponds to the hypothesis of the subduction nature of nitrogen in deep mantle plumes. [ABSTRACT FROM AUTHOR]

Authors' original continuously updated database, which currently comprises data from 22 300 publications on mineral-hosted fluid and melt inclusions, is used to generalize data on the physicochemical parameters of processes that produced fluorite and barite deposits. The paper presents data on the following parameters of the fluids: temperature, pressure, density, salinity, and gas composition. The average composition (Н2О, CO2, CH4, N2, H2S, and CnHm) of fluids at fluorite–barite deposits is calculated. The paper reports the average composition of major gas components (CO2, CH4, N2, and H2S) of natural fluids at these deposits on the basis of Raman spectroscopic analyses of individual inclusions. Average F, S, and Ba concentrations are calculated for silicate magmatic melts and natural mineral-forming fluids. [ABSTRACT FROM AUTHOR]

The paper completes our summary of literature data on the physicochemical parameters and characteristics of the chemical composition of mineralizing fluids at endogenous gold deposits. The average values and variation limits of the temperature (50–845°С, mean 290°C), pressure (20–3600 bar, mean 600 bar), and salinity (0.1–88.0 wt % equiv. NaCl, mean 13.1 wt % equiv. NaCl) of fluids of Cenozoic gold deposits are estimated. The inherent features of the gas composition of the mineralizing fluids of these deposits are revealed. Parameters of mineralizing fluids at Cenozoic gold deposits are discussed in comparison with the analogous parameters of fluids at Archean, Proterozoic, Paleozoic and Mesozoic gold deposits. The chemical composition and parameters of mineral-forming fluids of gold deposits were determined to systematically evolve with time. Cenozoic gold deposits generally differ from older gold deposits in having a higher fluid temperature and salinity, lower pressure, and the highest value of the CO2/CH4 ratio. The decrease in fluid pressure from ancient gold deposits to younger ones may be associated with differences in the erosion depths of ancient and young mineralizing systems. [ABSTRACT FROM AUTHOR]

The paper addresses a fluid phase conserved in inclusions in diamond, which were synthesized in the metal–carbon system in the presence of silicate material at 5.5 GPa and 1500°C. Natural olivine and alkaline basaltic glass were used as silicate material. It was found that the diamonds contain 130 different volatile compounds dominated by medium (С5–С12) and heavy (С13–С18) aliphatic hydrocarbons, which correspond to the presence of a highly reducing fluid in the crystallization medium. The comparison of obtained data with composition of fluid inclusions, which were found in natural diamonds and contain significant amount of medium and heavy aliphatic hydrocarbons of the С5–С18 series, indicates that some natural diamonds could be formed in highly reducing mantle conditions in the presence of metal liquids. [ABSTRACT FROM AUTHOR]

The paper summarizes data on germanium and gallium concentrations in natural magmatic melts as follows from analyses of mineral-hosted inclusions and quench glasses in volcanic rocks. Germanium concentrations in melts vary from 0.96 to 17.6 ppm (1472 determinations). The geometric mean germanium concentration in silicate melts is 1.56 ppm, which is quite close to the clarke value. Concentrations of gallium in magmatic melts vary from 0.47 to 495 ppm (8755 determinations). The geometric mean of gallium concentration in silicate melts is 19.0 ppm, which is also close to the clarke value. Germanium concentration in hydrothermal fluids ranges from 0.01 to 930 ppm (405 determinations), and the geometric mean value is 17.0 ppm. Concentrations of gallium in fluids vary from 0.02 to 320 ppm (441 determinations), with a geometric mean of 2.0 ppm. The possible reasons for the differences in germanium and gallium concentrations in natural melts and fluids are discussed. [ABSTRACT FROM AUTHOR]

This paper continues a series of our earlier publications summarizing literature data on the physicochemical parameters and chemical composition of fluids at endogenic gold deposits and presents estimated average values of the temperature, pressure, and salinity of fluids, and variations in these parameters, at Mesozoic gold deposits. Parameters of mineralizing fluids at the Mesozoic deposits are discussed in comparison with the analogous parameters of fluids at Archean, Proterozoic, and Paleozoic gold deposits. The Mesozoic deposits are determined to generally differ from the older deposits in having fluids of higher temperature and lower pressure, with carbon dioxide in these fluids dominating over other gases. [ABSTRACT FROM AUTHOR]

Abstract—: The paper presents pioneering data on the isotopic composition and elemental ratios of nitrogen, carbon (carbon dioxide), helium, and argon in the fluid phase of quenched tholeiitic glasses from different segments of the Bouvet Triple Junction area (BTJ). The data reflect a complicated geodynamic and tectonic history of the area evolution and indicate that the variations in the elemental ratios of the volatile components of the fluid-gas phase were controlled by a number of various factors: elemental fractionation during melt degassing, mixing of gases from different sources, postmagmatic diffusion-controlled helium loss. The nitrogen-argon and noble gas isotope systematics suggest a significant contribution of the atmospheric component to the mantle source of fluids for the samples from the Spiess Ridge and the segment of the Southwest Indian Ridge (SWIR) and a smaller contribution for the Mid-Atlantic Ridge (MAR) samples. For the Spiess Ridge and SWIR, the most probable contaminating agent was water fluid with dissolved gases of atmospheric composition. This fluid may have been brought to the mantle with ancient crustal rocks involved in magma generation. These crustal rocks may represent small fragments of the Gondwana continent with which sedimentary organic matter could be brought into the magma source. [ABSTRACT FROM AUTHOR]

Abstract: This paper continues the generalization of literature data on physicochemical parameters and chemical features of fluids of endogenous gold deposits. The average values and ranges of temperature, pressure, and salinity of fluids from Paleozoic gold deposits are estimated. Peculiarities of gas composition of ore forming fluids at these deposits are revealed. Parameters of mineral-forming fluids of Paleozoic gold deposits are compared with those of Archean and Proterozoic gold deposits. [ABSTRACT FROM AUTHOR]

Abstract: Physicochemical parameters under which hydrothermal Sb, As, and Hg deposits are formed are estimated using data from a database (which was compiled and continuously updated by the authors and includes data from more than 21 500 publications on mineral-hosted fluid and melt inclusions). The discussed parameters of the fluids are their temperature, pressure, density, salinity, and gas composition. The paper reports data on the temperature, pressure, and salinity of fluid inclusions in ore minerals (antimonite, orpiment, realgar, and cinnabar) and the calculated average composition of the dominant fluid components of natural fluids (CO2, CH4, N2, and H2S) at Sb, As, and Hg and, for comparison, at Au, Sn, W, Cu, Pb, and Zn deposits. The compositions of individual inclusions in minerals and chill glasses of rocks are utilized to calculate mean As and Sb concentrations in magmatic silicate melts of mafic, intermediate, and acid composition. Data are reported on the calculated Sb, As, and Hg concentrations in natural mineral-forming fluids. [ABSTRACT FROM AUTHOR]

The paper discusses specifics of gas separation techniques by means of sample crushing in vacuum, and, in particular, the stepwise crushing method for studying the sources and evolution of the fluid phase of rocks and minerals. The data on the Seblyavr massif, Kola Peninsula, are employed to demonstrate that, if the age of the minerals is old enough and they contain elevated concentrations of parental elements (U, Th, and K), in situ produced noble gas components can strongly distort the composition of the initially entrapped gases and thus result in misinterpretations of the analytical data. The application of stepwise crushing technique, as well as an individualized approach to data interpretation for each of the samples, makes it possible to solve the problem. [ABSTRACT FROM AUTHOR]

The paper presents data on the average analyzed concentrations of volatile components (CO2, CH4 and other hydrocarbons, N2, and H2S) in natural fluids producing hydrothermal Au, Sn, W, Mo, Cu, Pb, and Zn mineral deposits. Characteristics of the gas regime at these deposits are determined. Thermodynamic simulations are carried out to model how compounds with volatile components are formed when water interacts with silicic and mafic rocks within wide P-T ranges. The speciation of volatile components determined by direct analysis is in good agreement with numerical simulations of water-rock systems (for silicic and mafic rocks). More reduced species with volatile components are formed in mafic rocks. [ABSTRACT FROM AUTHOR]

This paper analyzes literature data on physicochemical parameters and chemical composition of fluids of Precambrian endogenous gold deposits. The average values and ranges of temperature, pressure, and salinity of fluids from the Archean and Proterozoic gold deposits are estimated. It is revealed that fluids of Archean deposits are dominated by methane, while those of Proterozoic deposits, by nitrogen. It is proposed that the accumulation of nitrogen in the atmosphere is related to the intense nitrogen degassing from the Earth's interior. The highest pressures of endogenous fluids in this period could reflect specifics of deep geodynamics of the planet in the Proterozoic. The large gold deposits (>100 tons) are characterized by narrower range of physicochemical parameters as compared to small deposits. The contribution of heated chloride brines in the formation of majority of large Proterozoic deposits is established. [ABSTRACT FROM AUTHOR]

The paper presents data on an original equipment complex, consisting of two apparatuses, designed to prepare rock and mineral samples for the isotopic analysis of their fluid and/or gas inclusions. An example of samples from the Guli alkaline ultramafic massif in the Maimecha-Kutui province, northern central Siberia, is employed to demonstrate the capabilities of the technique of stepwise sample crushing and multiple-isotope analysis of the fluid phase. [ABSTRACT FROM AUTHOR]

Information from a database, which was compiled and continuously updated by the authors of this paper and now includes information from 19500 publication on fluid and melt inclusions in minerals, is used to summarize results on the physicochemical formation parameters of hydrothermal Au, Ag, Pb, and Zn deposits. The database provides information on fluid inclusions in minerals from 970 Pb-Zn, 220 Au-Ag-Pb-Zn, and 825 Au-Ag deposits in various settings worldwide. Histograms for the homogenization temperatures of fluid inclusion are presented for the most typical minerals of the deposits. In sphalerite, most homogenization temperatures (1327 measurements) of fluid inclusions lie within the range of 50-200°C with a maximum at 100-200°C for this mineral from Pb-Zn deposits and within the range of 100-350°C (802 measurements) with a maximum at 200-300°C for this mineral from Au deposits. Data are presented on fluid pressures at Au (1495 measurements) and Pb-Zn (180 measurements) deposits. The pressure during the preore, ore-forming, and postore stages at these deposits ranged from 4-10 to 6000 bar. The reason for the high pressures during preore stages at the deposits is the relations of the fluids to acid magmatic and metamorphic processes. More than 70% of the fluid pressures values measured at Pb-Zn deposits lie within the range of 1-1500 bar. Au-Ag deposits are characterized by higher fluid pressures of 500-2000 bar (61% of the measurements). The overall ranges of the salinity and temperature of the mineral-forming fluid at Au-Ag (6778 measurements) and Pb-Zn (3395 measurements) deposits are 0.1-80 wt % equiv. NaCl and 20-800°C. Most measurements (∼64%) for Au-Ag deposits yield fluid salinity <10 wt % equiv. NaCl and temperatures of 200-400°C (63%). Fluids at Pb-Zn deposits are typically more saline (10-25 wt % equiv. NaCl, 51% measurements) and lower temperature (100-300°C, 74% measurements). Several measurements of the fluid density fall within the range of 0.8-1.2 g/cm. The average composition of volatile components of the fluids was evaluated by various techniques. The average composition of volatile components of fluid inclusions in minerals is calculated for hydrothermal W, Au, Ag, Sn, and Pb-Zn deposits, metamorphic rocks, and all geological objects. The Au, Ag, Pb, and Zn concentrations in magmatic melts and mineral-forming fluids is evaluated based on analyses of individual inclusions. [ABSTRACT FROM AUTHOR]

Colloids of metals have been studied much more poorly in hydrothermal solutions than in surface and underground waters. Nevertheless, literature data indicate that colloidal particles containing metals are present in hydrothermal minerals, in geogas, in groundwaters above orebodies, in fluid inclusions of minerals, and in geothermal solutions. These particles are usually thought to be formed at nucleation in supersaturated solution, which is generated in conversion reactions of minerals or when fluids boil. Published experimental data confirm that colloidal particles can be formed and preserved in hydrothermal conditions. Experimental data on the filtration of supersaturated and colloidal solutions in porous media at elevated temperatures are still too scarce to enable a comprehensive and reasonably accurate assessment of the mobility of colloidal particles under these conditions. The involvement of colloids in the hydrothermal ore-forming process is most clearly manifested at formation of rich epithermal Au deposits. The example of a quartz geothermometer is employed to demonstrate that metals can be transferred in true supersaturated solution, and this mechanism may be even more efficient than colloidal transfer. Metals can thus be transferred in the hydrothermal process in significantly higher concentrations than it follows from the traditional approach based on equilibrium thermodynamics. [ABSTRACT FROM AUTHOR]

The native gold in the Woxi Au–Sb–W deposit is characterized by remarkably high purities (99.9%), called as super-pure native gold. The deposit can thus be used as the suitable application example for analyzing ore-forming conditions by using the thermodynamic calculation of AuxAg1 – x-fluid equilibria. According to experimental results of minerals and fluid inclusions, some physicochemical conditions are assumed in the thermodynamic calculation of the fluids equilibrated with Au–Ag solid solutions of XAu = 0.999. Calculated results in log fO2-pH diagrams show dissolved gold and silver concentrations, as well as stability fields of pyrite and sericite associated with the super-pure native gold. On the other hand, LA-ICP-MS analysis indicates that both Au and Ag concentration are determined in the fluid inclusions of scheelite, showing varied Au/Ag ratios with different homogenization temperatures. The calculated results assumed by different data of inclusions in scheelite, indicate two fluid inclusions showing higher homogenization temperatures (303°C and 356°C) and higher Au/Ag ratios are possible for precipitation of the super-pure native gold coexisting with pyrite and sericite, whereas one fluid inclusion showing a lower homogenization temperature (198°C) and a lower Au/Ag ratio is impossible for the super-pure native gold. Therefore, the super-pure native gold in the Woxi deposit was probably formed by the hydrothermal fluid with higher Au/Ag ratios and high temperatures in the mineralization stage of scheelite. [ABSTRACT FROM AUTHOR]

Thermodynamic modeling was carried out for the formation of Mo–W ores at the Kalguty deposit (Gornyi Altai). The modeling was based on the physicochemical conditions of Mo–W ore formation estimated from fluid inclusion data. Quartz–wolframite veins of the deposit were formed under the influence of homogeneous reduced carbonate–chloride fluids, which showed elevated W and Sb concentrations. Pyrite–chalcopyrite–molybdenite mineralization was formed under the influence of heterogeneous oxidized sulfate–carbonate–chloride fluids enriched in Cu, Mo, W, Bi, and S. The economic combined greisen–vein Mo–W (Be) mineralization of the Kalguty deposit was formed by the superposition of molybdenite–chalcopyrite mineralization on the mineral assemblages of earlier quartz–wolframite veins. Ore forming processes were modeled for the scenarios of isobaric cooling and rock–solution interaction in the presence of oxidized and reduced model solutions corresponding to the natural ore-forming fluids of the Kalguty deposit. The results of thermodynamic modeling allowed us to conclude that rock interaction with oxidizing acid solution enriched in Cu, Mo, Bi, W, and S is the most plausible model for the formation of the greisen Mo–W ores. The interaction was accompanied by the inversion of the Eh–pH parameters of oxidizing ore-forming fluid and changes in its metal content, salt composition, and gas components. The chalcopyrite–molybdenite mineralization was formed during cooling of hot (>400°C) metalliferous oxidizing acid fluids before the inversion of their Eh–pH parameters. Wolframite ores could be deposited from the same portion of ore-forming fluid after the Eh–pH inversion and cooling. The combined Mo–W mineralization of the Kalguty deposit could result from at least two hydrothermal rhythms characterized by similar physicochemical parameters of ascending ore-forming fluids. The level of ore formation of each successive hydrothermal rhythm moved upward. This resulted in the telescoping of the high-temperature chalcopyrite–molybdenite mineralization by the earlier wolframite mineralization. The obtained data indicate the significance of probable vertical movement of the ore formation zone during the multistage mineralization process for the development of certain sequences of formation of mineral assemblages observed in ore deposits. [ABSTRACT FROM AUTHOR]

New data were obtained on the chemical composition of beryl from the Suprunovskoye deposit (wt %): 66.10 SiO2, 0.51 Na2O, 17.99 Al2O3, 0.37 MgO, 0.03 K2O, 0.02 CaO, 0.58 FeO, and 13.70 BeO (calculated). Fluid and melt inclusions were investigated for the first time in this mineral. It was found that the beryl was formed during late stages of granite magmatism from a specific pegmatite silicate melt or a water–silicate liquid enriched in water (>7 wt %), heavy REE (La/Yb = 0.48), and lithium, and depleted in fluorine and boron at a temperature of ~700°C and a pressure of ~6 kbar. [ABSTRACT FROM AUTHOR]

Physicochemical parameters of the origin of Cu and Mo deposits are reviewed based on an original database that currently includes information from more than 21000 publications on fluid and melt inclusions hosted in various minerals. The deposits are classified into three types: (i) Cu-Mo (usually porphyry), (ii) Cu (usually without Mo but often with base metals), and (iii) Mo (without Cu but often with Be and W). For these deposits, the temperature and pressure of their origin and the density, salinity, and gas composition of the fluids are discussed. The average composition of the dominant volatile components of natural fluids is reported for Cu and Mo deposits and is compared with the composition of volatiles in fluids at Au, Sn, W, Pb, and Zn deposits. Data on individual inclusions are used to evaluate the Cu and Mo concentrations in the magmatic silicate melts and mineral-forming fluids. [ABSTRACT FROM AUTHOR]

The Pohrenk fluorite mineralisation which makes up Central Anatolia's most extensive fluorite region is Lutetian aged, and hosted in carbonate rocks that have undergone occasional karstification and silicification along a N-S fault trend. Fluid inclusion values and the position of fluorites in the Tb/La-Tb/Ca diagram show that mineralisation occurred in a hydrothermal environment with homogenisation temperatures ranging from 78.1-363°C. The presence of fluorite as a space filler in carbonate rocks and its association with silicification indicates that the solutions contained considerable amounts of Si alongside F (fluorine). The Pohrenk fluorite samples have Nd/Nd values of between 0.512349 and 0.512497, whilst Sr/Sr values vary between 0.708161 and 0.708772. These values indicate a mantle origin where continental contamination could occur. When the Nd-Sr values are compared to magmatic and young volcanics, the Pohrenk fluorites are seen to be enriched and exhibit similar isotopic signatures to Upper Cretaceous aged magmatics, Early-Middle Miocene volcanics and Mio-Quaternary volcanics. [ABSTRACT FROM AUTHOR]

We generalize, for the first time, published and original data on the gallium concentrations in natural magmatic melts and fluids obtained by studying quenched glasses in volcanic rocks and inclusions in minerals. Based on 2688 determinations, gallium concentrations in magmatic melts vary between 0.47 and 495 ppm at average content of 18.0 ppm (+4.2/-3.4). Gallium concentrations in magmatic melts generated in different geodynamic settings show different distribution. Minimum concentrations (on average, 16.0 ppm, +3.6/-2.9) are typical of the island-arc melts, while maximum contents were determined in melts of oceanic islands (on average, 29.1 ppm, +13.4/-9.2) and intracontinental rifts and hot spots (26.5 ppm, +25.4/-13.0). Published and new 339 determinations of gallium concentrations in natural fluids indicate the wider range of their variations as compared to those of melts: from 0.02 to 11260 ppm, at average 1.6 ppm (+10.8-1.4). The possible gallium fractionation in fluid-magmatic systems is discussed. [ABSTRACT FROM AUTHOR]

The mixing of gas and aqueous fluid in hydrothermal ore-forming processes is discussed with reference to gold deposits to demonstrate that this phenomenon may affect ore deposition. Data on fluid inclusions in samples from the Sukhoi Log and Olimpiadinskoe deposits in Russia are utilized to demonstrate possible implications of gas mixing with hydrothermal solution when gold ores are formed. A simplified thermodynamic model is suggested to show how interaction between aqueous saline solutions with pure carbon dioxide or carbon dioxide-methane mixture may affect gold solubility. Further studying such processes may provide interesting information for understanding the genesis of ore mineralization. [ABSTRACT FROM AUTHOR]

An original database, which was compiled by the authors, is continuously updated, and now contains data from more than 19 800 publications on fluid and melt inclusions in minerals, was utilized to review and synthesize data on the physicochemical parameters at which hydrothermal uranium deposits and occurrences were formed. The parameters discussed below are temperature, pressure, density, salinity, gas composition of the fluid, and U concentration in the hydrothermal fluid. The database contains data of fluid inclusions in minerals from 90 U deposits and occurrences worldwide. Histograms of the homogenization temperatures of fluid inclusions are presented for such typical minerals of these deposits and occurrences as quartz, calcite, and fluorite. The temperature range most favorable for the origin of U deposits is 100-200°C (67% of the 937 measured temperature values fall within this range), which makes U deposits remarkably different from higher temperature Au-Ag, W, and Sn deposits. These deposits also differ in the salinity of the fluids. The range of fluid salinity of 10-30 wt % equiv. NaCl includes 42% of fluid salinity values measured at U deposits (our database includes 937 measured values), 27% for Au-Ag deposits (10 237 measured values), 27% for W deposits (2333 measured values), and for Sn deposits (1981 measured values). The relatively low temperature of U-bearing fluids and their high salinity testify that these solutions had a high density: 94% of all measured values lie within the range of 0.8-1.2 g/cm. Fluid pressure at U deposits broadly varied from 2500 to 300 bar and perhaps even lower values. Data on the chemical composition of the gas phase of the fluid inclusions show a significant diversity of the fluids contained in the inclusions. In certain instances, HO-CO fluids give way to fluids rich in CH and N with minor amounts of hydrocarbons. Data are reported on the gas composition of fluid inclusions in the nuclear-reactor zone at three Precambrian U deposits. Analyses of individual inclusions were utilized to evaluate U concentrations in magmatic melts and mineral-forming fluids. The geometric mean U concentration in silicate melts of composition ranging from ultramafic to silicic is 0.92 ppm (8053 measured values), and the analogous values for the fluids is 1.21 ppm (271 measured values). [ABSTRACT FROM AUTHOR]

Orthopyroxene, clinopyroxene, and olivine from a metasomatized mantle xenolith of garnet lherzolite in alkaline rocks at the Jetty Oasis, East Antarctica, contain numerous carbon dioxide-dominated composite melt-fluid and fluidized sulfide-silicate (±carbonate) inclusions. Although the maximum pressure under which the inclusions were captured by rock-forming minerals was evaluated at 13 kbar, its actual value should have been much higher, judging by the fact that the inclusions have lost part of their material (decrepitated) when the xenolith was brought to the surface. Two major fluid populations are distinguished. The fluids entrapped during the earlier episode have a more complicated composition. Dominated by CO, these fluids contain much N (0.1-0.2 mole fractions), HS, and perhaps, also HO and are hosted by sulfide-silicate (±carbonate) inclusions produced by liquid immiscibility. As these inclusions evolved, they enriched in CO and depleted in HS and N. Although the concentrations of N, HS, and HO were generally relatively low, these components played an important role in mantle metasomatism, as is reflected in the geochemistry of the derived magmas. The fluids of the younger episode (pressures lower than 7 kbar) are notably richer not only in CO but also in HO (up to the appearance of inclusions with a liquid aqueous phase and the formation of CO gas hydrate when cooled in a cryometric stage by liquid N). The effect of fluids on the mantle source in two discrete episodes is also confirmed by isotopic-geochemical data. Isotopic data on gases obtained immediately from fluid inclusions in minerals by the stepwise crushing technique provide evidence of the evolution of elemental and isotopic ratios of the gases in the course of the metasomatic processes. The high-pressure fluid inclusions of the earlier episode have low C/N, C/Ar, and N/Ar ratios, isotopically heavy N, and somewhat elevated (to 530) Ar/Ar ratios. The younger fluids typically have higher (by two to three orders of magnitude) C/N and C/Ar ratios, lower δC of CO, and N/Ar and Ar/Ar ratios close to the atmospheric values. The nitrogen and argon isotopic compositions and elemental ratios suggest that the younger fluids could have been produced by two-component mixing in the mantle-atmosphere system. Comprehensive analysis of the data and in particular the Ar/Ar ratios, which are atypical of the mantle, and an increase in the HO concentration, suggests a subduction-related nature of the fluids. [ABSTRACT FROM AUTHOR]

Special methodology was used to study the distribution of REE and some other elements in zoned fluorites from the different deposits of Eastern Transbaikalia. Fluorites from the uranium and polymetallic ore fields sharply differ in their REE distribution pattern and the composition of fluid inclusions, which reflects the geochemical specifics and indicates the possible sources of parental solutions. A gradual change in REE distribution patterns established in the successive growth zones of fluorites clearly coincides with the gradual decrease of temperature and mineralization of fluid inclusions. It is suggested that a change in the REE distribution pattern was provoked by the crystallochemical differentiation related to the formation of nano-sized mineral admixtures of REE phosphates and/or fluorcarbonates, which possess an ability to the selective accumulation of different REE groups. It was found that the zoned fluorites from the Streltsovka and Garsonui deposits show an opposite trends in the change of REE pattern with zonation. With a general decrease in total REE contents, fluorite from the Streltsovka deposit shows a change from positive parabolic to subchondritic pattern, while that from the Garsonui deposit, varies from the negative via subchondritic to the positive patterns. [ABSTRACT FROM AUTHOR]

Comprehensive microthermometric investigations revealed similar temperature ranges (280-120°C) for the formation of late carbonates in the Khokhlovskoe, Semizbai, and Malinovskoe deposits of the West Siberian uranium ore region. A close chemical similarity was definitely established between the solutions of fluid inclusions and thermal nitrogen-methane waters with elevated CO concentrations typical of this region in general. It was noted that such CO-rich mineral waters (Yessentuki no. 4 type) are common in the Mesozoic sequences of the Shadrinsk region, where Transuralian uranium deposits occur, and are similar in composition and temperature to the modern CO-rich formation waters of the host sequences of the Khokhlovskoe deposit. The mineralogical and geochemical features of newly formed late minerals and uranium ores were considered as the most probable reflection of the exfiltration of such thermal solutions into the host levels. Two late mineral assemblages were distinguished: (1) hematite-calcite and (2) goethite-berthierine and goethite-smectite-chlorite with siderite or goethite-kaolinite-illite with siderite; they occur both in the host sequences and in the underlying basement rocks. The development of the latter assemblage causes a significant change in rock color (bleaching); it is widespread and was observed in all the deposits. It was shown that these altered rocks and uranium ores (especially high-grade) are very similar in mineral and chemical composition to the products of acid leaching and accompanying mineralization, which could be related to low-temperature argillization. It was suggested that exogenic epigenetic processes of ancient soil-bedrock oxidation contributed certainly to the development of uranium mineralization, and the modern character of the uranium ores and their host rocks is related to a large extent to the influence of hydrothermal CO-rich solutions related to the neotectonic activation of the region. This resulted in the development of their specific mineral and chemical compositions and corresponding technological characteristics. It seems expedient to estimate the possible contributions of exogenic and endogenic factors to the formation of the uranium mineralization rather than oppose the roles of these processes of different stages. [ABSTRACT FROM AUTHOR]

The article discusses a study on the behaviors of microorganisms in fluid inclusions contained in quartz. It states that the inclusion comprises gas bubble, aqueous solution, and dark elongated phases which are firm at room temperature. It mentions that the heating of the inclusion results to the intense movement of the bacteria. It adds that the movements of the bacteria continued and remained in similar manner until the solution was frozen completely at 30° C temperature.

The author's database, which presently includes data from more than 18500 publications on fluid and melt inclusions in minerals and is continuing to be appended, was used to generalize results on physicochemical parameters of the formation of hydrothermal deposits and occurrences of tin and tungsten. The database includes data on 320 tin and tin-tungsten deposits and occurrences and 253 tungsten and tungstentin deposits around the world. For most typical minerals of these deposits (quartz, cassiterite, tungsten, scheelite, topaz, beryl, tourmaline, fluorite, and calcite), histograms of homogenization temperatures of fluid inclusions were plotted. Most of 463 determinations made for cassiterite are in the range of 300-500°C with maximum at 300-400°C, while those for wolframite and scheelite (453 determinations) fall in the range of 200-400°C with maximum at 200-300°C. Representative material on pressures of hydrothermal fluids included 330 determinations for tin and 430 determinations for tungsten objects. It was found that premineral, ore, and postmineral stages spanned a wide pressure range from 70-110 bar to 6000-6400 bar. High pressures of the premineral stages at these deposits are caused by their genetic relation with felsic magmatism. Around 50% of pressure determinations lie in the range of 500-1500 bar. The wide variations in total salinity and temperatures (from 0.1 to 80 wt % NaCl equiv and 20-800°C) were obtained for mineral-forming fluids at the tin (1800 determinations) and tungsten (2070 determinations) objects. Most of all determinations define a salinity less than 10 wt % NaCl equiv. (∼60%) and temperature range of 200-400°C (∼70%). The average composition of volatile components of fluids determined by different methods is reported. Data on gas composition of the fluids determined by Raman spectroscopy are examined. Based on 180 determinations, the fluids from tin objects have the following composition (in mol %): 41.2 CO, 39.5 CH, 19.15 N, and 0.15 HS. The volatile components of tungsten deposits (190 determinations) are represented by 56.1 CO, 30.7 CH, 13.2 N, and 0.01 HS. Thus, the inclusions of tungsten deposits are characterized by higher CO content and lower (but sufficiently high) contents of CH and N. The concentrations of tin and tungsten in magmatic melts and mineral-forming fluids were estimated from analysis of individual inclusions. The geometric mean Sn contents are 87 ppm (+ 610 ppm/−76 ppm) in the melts (569 determinations) and 132 ppm (+ 630 ppm/−109 ppm) in the fluids (253 determinations). The geometric mean W values are 6.8 ppm (+ 81/−6.2 ppm) in the magmatic melts (430 determinations) and 30 ppm (+ 144 ppm/−25 ppm) in the mineral-forming fluids (391 determinations). [ABSTRACT FROM AUTHOR]