Fluid Inclusions In Minerals Research Articles

Fluorescent emission and nondestructive 3D textural imaging in geologic materials by multiphoton microscopy

This work greatly expands the application of multiphoton microscopy to geological investigations by using a tightly focused femtosecond laser beam to excite fluorescent emissions among minimally prepared rock and mineral samples. This novel finding provides a tool for spatially resolving UV-visible fluorescent sources in minerals. Through a combination of harmonic generation and fluorescence, unique opportunities are made available for mineralogical investigations of terrestrial rocks and astromaterials. This report includes the first demonstrations for 3D imaging of fluid inclusions in minerals and radiation-induced luminescence imaging in meteorites. Nonlinear optical mineralogy, enabled by multiphoton microscopy, provides unique insights into mineralogic samples and holds the potential to revolutionize the analysis of geologic and astromaterials samples in the coming years.

Fluid inclusions in minerals: from geosciences to the physics of water and back

Natural mineral samples often contain small volumes of trapped fluid material. They carry information about the history of the host mineral and its environment, and for this reason are used by geoscientists. Physicists and physico-chemists have successfully harnessed water inclusions in quartz to bring liquid water to a metastable state, at a pressure well below its equilibrium pressure with vapor. The pressure can reach negative values as large as -140 MPa, which exceeds by far the limits of other techniques, and approaches the theoretical threshold for spontaneous nucleation of a vapor bubble. This has enabled a deeper understanding of nucleation and of the anomalies of water. In turn, the optical techniques developed to study water’s properties have recently found a new application in the reconstruction of palaeotemperatures in surface processes. I review here some aspects of fluid inclusions, these fascinating objects at the crossroads between disciplines.

Mineral Crushing Methods for Noble Gas Analyses of Fluid Inclusions

Noble gases are frequently probed for investigating fluid inclusions in minerals to unravel rock-forming processes through time. Over the last decades, heating and crushing have been the two main methods applied for noble gas extraction from fluid inclusions in ultrahigh vacuum (about 10-9 mBar). The heating of minerals or pieces of bulk rock causes the release of noble gases from both fluid inclusions and the mineral or rock matrix, the latter due to temperature-dependent mineral dehydration. Crushing of minerals only affects fluid inclusions and allows a release of noble gases at room temperature with minor contributions from the mineral matrix. This review describes different ultravacuum crushing techniques for noble gas analysis from fluid inclusions. It examines the technical details and operational conditions of each crushing system as well as methods to prepare samples prior to crushing. Crushing systems were found to have unique designs across the different laboratories reviewed; they include single or multiple sample loadings and manual, magnetic, or hydraulic operation of the crushing pistons. Due to the small amounts of noble gases released, the technology requires several mg to a few grams of rock material to achieve a measurement of all stable noble gas isotopes in a single fluid inclusion. While theoretically all stable noble gas isotopes are of interest, the elements and isotopes reported in different studies vary widely and reference materials as well as laboratory intercomparisons are lacking. The review includes applications on the origins of magmatic rocks and geochemical processes in the Earth’s mantle, the origin and chemical composition of deep crustal fluids and how these contribute to the formation of minerals of economic interest, and paleoclimate studies based on speleothems.

Transfer of Metals under Hydrothermal Conditions in the Form of Colloidal Particles and Supersaturated True Solutions

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.

Important and useful facts on fluid inclusions in minerals in the context recognition of hydrocarbon systems

Important and useful facts on fluid inclusions in minerals in the context recognition of hydrocarbon systems

In-situ laser ablation of mineral fluid inclusions: Evaluating the effects of solid and liquid matrices, laser repetition rate and fluence on data quality

Fluids play an important role in many geological/ore genetic processes. The composition of the hydrothermal fluid is a critical but often unknown parameter that controls the mobilization of elements and their concentration into mineralized zones. In-situ analyses of fluid inclusions trapped in minerals using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) is a powerful tool to constrain the composition of the mineralizing fluid. The LA-analysis of fluid inclusions is analytically challenging due to potential mismatch of matrix between fluid inclusions and solid NIST reference glasses commonly used as calibrating standards. We conducted experiments to evaluate the effects of using solid and liquid as calibrating standard on data quality during ablation of liquid/mineral fluid inclusions, as well as the effects of variable energy fluence and repetition rate on the time-dependent elemental fractionation. The LA-analyses of liquids (with NaCl matrix) when standardized against another solution has lower precision and accuracy compared to standardization with NIST reference glasses. The 193 nm laser has little matrix effect and causes negligible elemental fractionation. The trace element concentrations of liquids retrieved by external standardization with NIST reference glass has better accuracy and precision. Higher laser fluence (8.5 J/cm2) produces better sensitivity, lesser time-dependent elemental fractionation, lower detection limits, and better accuracy/precision and is recommended for ablation of natural fluid inclusions or liquids. We tested our preferred analytical protocol by analyzing the composition of quartz-hosted fluid inclusions from the Malanjkhand copper deposit in central India. The LA-ICPMS measurements of the fluid inclusions help to establish that the mineralizing fluid had high concentrations of K, Rb, and Cs. Fluid inclusions from the Malanjkhand copper deposit are trapped from fluids that are dominantly of magmatic origin, sourced from highly differentiated granitic magmas. The NIST glasses are appropriate calibrating standards for ablation of synthetic liquids as well as natural fluid inclusions.

Helium isotopes in Plinian and inter-Plinian volcanic products of Vesuvius, Italy

We investigated helium isotopes on gas extracted by crushing from melt and fluid inclusions in minerals from Plinian and inter-Plinian tephra and lavas of Vesuvius, Italy. Erupted products of different ages were considered, from Avellino eruption (1995 BCE) to the last eruption of 1944, with special focus on the 79 AD Plinian eruption. He/He 4 3 ratios between 1.5 and 2.7 RA were measured, with the highest values associated with rocks representative of the roof and the walls of the magma chambers (cumulates). Lowest values occurred in sanidines representative of magma-skarn interfaces. Noteworthy, the highest measured values of the 79 AD pumices were comparable with both lavas and tephra emitted from flank vents and under open-conduit conditions during the Medieval Period and Present Period of Vesuvius activity, and present-day fumarolic discharges. He 3/He 4 values are buffered within an extended, deep-seated reservoir at about 10 km filled with magma rising from the mantle. A fact that might potentially limit the accuracy of future eruption forecasting through monitoring of He/He 4 3 changes in Vesuvius fumaroles. Ageing and interaction with crustal rocks emerged as possible mechanisms that lowered the He/He 4 3 ratio of the melt during its intra-crustal magma chambers stay, with highest values associated with more dynamic conditions.

The role of CO2 flushing in triggering the ‘Millennium’ eruption and recent unrests at Changbaishan volcano (China/North Korea)

ABSTRACT The impact of large-scale caldera-forming eruptions on our society and climate can be considerable. The triggering mechanisms of these eruptions and the instability of their magmatic systems are still elusive. Here we use X-ray tomographic microscopy, glass geochemistry and volatile element concentration data on the products of the 946 CE ‘Millennium’ eruption (ME) of Changbaishan volcano (China/North Korea) with the aim to identify the triggering mechanism of the eruption. ME emitted rhyolites and trachytes whose textural parameters suggest vesiculation events related to crystallization and magma ascent in the conduit, and to the arrival of new gas in the magmatic system. Solubility models show that the CO2 and H2O dissolved in the glass are consistent with a pressure of 100–200 MPa. Literature data from fluid inclusions in minerals indicate that the residing magma was CO2 free before the eruption, whereas the CO2 content in the glass reaches 600 ppm at the flash of the ME event. We find that a single, shallow magma reservoir localized between 7.5 and 3.7 km depth in which rhyolites occupies the top and trachytes the bottom is fully destabilized by the arrival of external CO2-rich fluids. Such fluids are released from a deeper, carbonate-rich mantle source. Our results and those of independent geophysical data show that the ME magmatic system is still active, and the continuous upraising of fluids from depth may drive unrest episodes like that recorded in 2002–2006. Our findings elucidate the role of deep, mantle-derived fluids in driving large-scale explosive eruptions. We provide evidence that volcanic unrests may not mirror the internal dynamics of magmatic reservoirs.

FEATURES OF THE FLUID REGIME OF POSTSEDIMENTOGENIC PROCESSES DURING THE FORMATION OF GAS CAPACITY OF THE TRANSCARPATHIAN BASIN (WITHIN THE LIMITS OF UKRAINE)

Gases in migrating paleofluids of the Transcarpathian Basin in Ukraine proper were investigated. Their properties were analyzed using fluid inclusions in minerals and fluids occurring in closed pores of promising gas-bearing rocks. Samples were taken from wells drilled within the Mukachevo (1-Borodivsk-Novosilsk) and Solotvyno (1-Bushtyno, 4-Hrushovo, 1-Danylovo, 28-Solotvyno) depressions. According to the data from mass-spectrometric chemical analysis, methane and its homologues and carbon dioxide were found in the composition of volatile compounds, which coincides with the identified advantage of methane and its homologues, on the one hand, and carbon dioxide, on the other hand, in the natural gases of fields of the Transcarpathian gas-bearing area. Methane (98.2 vol. %), ethane (1.2 vol. %) and propane (0.6 vol. %) are found in fluid inclusions in calcite of veinlet in the rock from the well 28 of the Solotvyno structure, which includes the Solotvyno natural gas field. Only methane is found in closed rock pores. Natural gases of the Solotvyno gas field contain methane (53.86%), ethane (2.65%) and propane + butane (1.34-0.32%). СО2 contents as high as 97.3 vol. % occur in fluid inclusions in calcite of veinlets in rocks of the well 1 at Ruski Komarivtsi of the Mukachevo depression and 100 % in fluid inclusions in zeolite (?) from impregnates in rocks of the well 1 at Bushtyno of the Solotvyno depression. This can be explained by the activity of two different composition paleofluids, namely reduced or oxidating types present in bowels of the Transcarpathian Basin. They are associated with significant amount of reduced compounds (methane and its homologues) or a high concentration of oxidized compounds for their (mainly СО2). This was determined by differences in the composition of the primary high-energy abiogenic deep fluid: hydrocarbon-containing or carbon dioxide-containing. The gas composition of paleofluids indicates that two types of natural gas deposits may exist, mainly hydrocarbon or mainly carbon dioxide rich and, accordingly, the discovery of natural gas fields such as Solotvyno and carbon dioxide – such as Martovo. Hydrocarbon formation over a wide range of conditions and primary material ("oil polygenesis") allows the assessment of oil and gas resources of the region. A polygenetic approach for understanding hydrocarbon formation processes requires a changes in exploration strategy. More geochemical and thermobarometric research as well thermodynamic study of mineral-forming fluids is needed in promising geologic structures of the Transcarpathian gas-bearing area. This necessary, in order to predict possible occurrence of high-energy gas deposits and to determine areas for exploration.

Composition of volatiles of sulfide deposits and carbonate structures in submarine hydrothermal fields of the Mid-Atlantic Ridge

In this study, the composition of fluid inclusions in minerals from polymetallic sulfide deposits Ashadze-1, Semenov-2, Krasnov, Rainbow and from the Lost City carbonate structures of hydrothermal fields in the Atlantic Ocean was determined using pyrolysis-free gas chromatography–mass spectrometry.It was found out that sulfides and anhydrite from the hydrothermal ore crystallized in reducing conditions with the active participation of hydrocarbons, including high-molecular, sulfonated, nitrogenated and halogenated compounds as well as water and carbon dioxide.On the other hand, carbonate structures formed in considerably more oxidizing conditions, for which the main components of volatiles were СО2 and Н2О. The amount of detected hydrocarbons, including sulfonated, nitrogenated and halogenated compounds is significantly smaller compared to sulfides of ore vent structures.

Deep borehole disposal of intermediate-level waste

Abstract. Around the world, deep borehole disposal is being evaluated for intermediate-level waste (ILW), high-level waste (HLW), spent nuclear fuel (SNF), separated plutonium waste and some very high specific activity fission product waste. In Australia, long-lived ILW from research reactors and radiopharmaceutical production represents the principal waste stream that requires deep geologic disposal. Whilst the Australian government has not yet made a decision on its preferred strategy for ILW disposal, deep borehole disposal of small volumes of ILW would be a more cost-effective and modular solution compared to a conventional geologic disposal facility (GDF). CSIRO, ANSTO and SANDIA have created an international partnership to execute a full-scale borehole research, development and demonstration (RD&D) project in Australia. The project will demonstrate the technical feasibility of the long-term safety of borehole disposal in deep geological formations. The execution of this project could also demonstrate options for nuclear waste disposal that would reduce proliferation risks, potentially up to the termination of compliance with international safeguards requirements. The RD&D includes demonstration of surface handling and waste/seal emplacement capabilities, basic research on foundational science areas, and full-scale field testing in both a deep characterization borehole and a larger-diameter (0.7 m or 27.5 inch) 2000 m deep demonstration borehole. The multi-barrier system designed for such a deep disposal borehole concept places much less reliance on engineered barriers at the disposal zone to achieve safety as compared to a conventional GDF. It rather relies on geological features for waste containment. The concept being explored uses disposal containers with primary waste packages, such as vitrified waste canisters, inside; to be both cost effective and fit for purpose, such a container could have a mild steel-based structural component with copper coating. A critical review of six coating technologies showed that cold spray has the greatest advantages, such as minimal porosity and compressive residual stress. The RD&D has delivered novel enabling tools that assist with site screening, borehole design and post-closure safety assessments. For instance, an automated geological fault mapping and meshing tool was developed that assists with ranking the suitability of potential disposal sites based on proximity to faults. New codes were developed for better representation of fault zones in 2D/3D numerical flow and transport models, while also being more efficient to execute. Post-closure safety assessments tested the sensitivity of long-term safety with respect to disposal depth, rock permeability and sorption. Heat transport calculations explored the sensitivity of temperature evolution within the borehole to parameters such as heat load, borehole depth, geothermal gradients and rock thermal conductivity. For verification of host rock tightness while also demonstrating the absence of recent groundwater, a new noble gas analytical facility has been established for measuring rare noble gases in mineral fluid inclusions as indicators of very old pore fluids.

Fluid evolution of the Zhunuo porphyry Cu-Mo deposit in Gangdese Tract, Tibet, China: A fluid-inclusion investigation

The Zhunuo porphyry Cu-Mo deposit in the western part of south Gangdese porphyry copper belt (GPCB), Tibet, is a large porphyry system. The Cu-Mo mineralization of this deposit is mainly associated with a weakly aluminous I-type Miocene granite porphyry pluton that formed in a post-collisional extensional tectonic setting. Field observations and petrographic studies demonstrate that emplacement of the pluton took place in several intrusive pulses, each with associated hydrothermal activities. Early hydrothermal alteration produced a potassic assemblage, overprinted by later phyllic alteration. At least three main stages of mineralization have been identified: (1) early A stage quartz + K-feldspar + minor sulfide veins; (2) middle stage B1-subtype veins composed of quartz + molybdenite + sporadic sulfide and B2-subtype quartz + pyrite + chalcopyrite veins; and (3) late stage pyrite + quartz D veins.Three types of fluid inclusions (FIs) in quartz were identified in the early and middle stages (i.e., CO2 bearing-aqueous vapor (V)-type and liquid (L)-type, and solid (S)-type); only aqueous L-type FIs were observed in the late stage minerals. S-type FIs contain variable solid particles, including halite, calcite, anhydrite (or gypsum), and chalcopyrite, hematite, and an unidentified transparent crystal. Only halite was dissolved during heating. Halite-bearing S-type FIs were mainly homogenized by halite dissolution at 300–470°C (S2-type), corresponding to salinities of 38.9–56.3 wt% NaCl equiv.; and minor halite bearing S-type FIs were homogenized to liquid at 360–520°C via vapor disappearance (S1-type), with salinities of 31.9–56.7 wt% NaCl equiv. Other FIs in minerals of A, B1, B2 and D veins were homogenized at temperatures of 350–550°C, 303–500°C, 305–460°C, and 250–347°C with salinities of 3.4–20.9, 2.6–22.4, 4.8–21.8, and 4.7–18.2 wt% NaCl equiv., respectively. These data suggest that the ore fluids forming the Zhunuo deposit changed from high-temperature, low-moderate salinity, CO2-bearing magmatic fluids to low-temperature, low-salinity and CO2-poor meteoric fluids. Phase separation and cooling caused the precipitation of the abundant chalcopyrite in the middle stage B2-subtype veins. The molybdenite mineralization was caused mainly by the decrease of pressure due to the release of CO2, and by phase separation of fluid in the middle stage as recorded in the B2-subtype veins. This hydrothermal ore-forming system is different from other magmatic-hydrothermal systems in GPCB, but is similar to the typical Cu-Mo porphyry systems, which were initially CO2-bearing as indicated by the presence of abundant CO2-bearing, low-moderate salinity FIs and calcite-bearing S-type FIs.

Isotope-Geochemical Features of Apoultrabasic Metasomatites of the Sayan–Baikal Folded Area

Abstract —The paper is concerned with a geochemical study of apoultrabasic metasomatites of the Ospa–Kitoi, Parama, and Ust’-Kelyana ophiolite massifs located in the southern folded framing of the Siberian craton. The isotope (O, C, H, Sr, and Rb) systems of dunites, serpentinites, nephrites, listvenites, and talc–carbonate rocks are studied. The isotopic composition of oxygen in olivines from dunites is characterized by δ18O = 4.6–5.5‰. The δ18O values of serpentinites (4.67–7.35‰) point to the mantle genesis of fluids and might have been inherited from ultrabasic rocks. Nephrites are slightly enriched in heavy oxygen isotope (δ18O = 6.13–9.54‰). This indicates that their fluid phase was transported from serpentinites and captured a small portion of the crustal component. The widest variations in δ18O values, from 8.12 to 17.46‰, are observed in minerals from listvenites. Carbonates from these rocks show a highly heterogeneous isotopic composition of oxygen (δ18O = 12.9–18.8‰) and carbon δ13C = –2.8 to +2.8‰). These rocks formed with the contribution of metamorphogenic fluids. According to the isotopic composition of hydrogen, the examined serpentinites are divided into two groups: with δD values specific to “magmatic water” (δD = –73.50 to –85.00‰) and those typical of meteoric fluids (δD = –151.90 to –167.20‰). The listvenites are characterized by low Rb and high Sr contents. Their 87Sr/86Sr values (0.70702–0.70971) indicate the contribution of a crustal source. The study of fluid inclusions in minerals from listvenites has shown that the rocks formed under relatively low-temperature conditions. The homogenization temperatures of fluid inclusions in quartz and magnesite from listvenites of the Ospa–Kitoi massif are 184–290 ºC and 122–182 ºC, respectively. In the Parama massif, the homogenization temperature of fluid inclusions in quartz is 130–170 ºC. The solutions that formed listvenites of the Ospa–Kitoi massif were slightly saline (TDS = 2.9–8.4 wt.% NaCl eq.), with NaCl and Na2CO3 being the main salt components.

The Glafirinskoe and related skarn Cu-Au-W-Mo deposits in the Northern Altai, SW Siberia, Russia: Geology, igneous geochemistry, zircon U-Pb geochronology, mineralization, and fluid inclusion characteristics

The Glafirinskoe and related skarn Cu-Au (+Mo, W) deposits represent an Early Paleozoic (Late Cambrian to very early Ordovician) mineralization in the Altaid Belt, also known as the Central Asian Orogenic Belt. They are associated with multiphase plutons of high-K calc-alkaline to shoshonitic rocks that are related to a low-degree partial melting of metasomatically-enriched upper mantle, followed by amphibole fractionation in a deep (lower crustal ?) magma chamber and then by magma fractionation and emplacement at shallower crustal levels. Isotopic U-Pb zircon dating of the igneous rocks yields early Ordovician (ca. 480–478 Ma and 483 Ma) age. These rocks were emplaced in a continental magmatic arc after the Late Cambrian collision, in a post-collisional setting involving the stall and break-off of the subducting slab during the Late Cambrian to Early Ordovician.The deposits comprise prograde and retrograde skarns that are characterized by abundant andradite-rich garnet, which defines their oxidized type. Wider zones of potassic (quartz-K-feldspar) and calc-potassic (quartz-K-feldspar-calcite-garnet) alteration occur in the igneous rocks, with their further overprint by propylitic (with abundant scapolite) and phyllic (carbonate-phyllic) alteration. All these alteration assemblages bear abundant chalcopyrite and minor bornite. Phyllic alteration assemblages also contain various As, Sb, Pb, Zn, Co, Ni sulfides and sulfosalts, tellurides, Bi minerals, and native Au. Scheelite and/or molybdenite are locally present in some mineralized zones. The Cu-Au-Mo(-W) mineralization occurs as skarn orebodies that are spatially associated with porphyry-style alteration assemblages reflecting the high exploration potential for additional, but concealed, skarn-porphyry Cu-Au-Mo deposits in the vicinity.The retrograde skarn and potassic (calc-potassic) alteration assemblages were formed from high temperature (570–580 °C), high salinity, aqueous chloride magmatic-hydrothermal fluid, with its boiling and phase separation indicating hydrostatic conditions at a relatively deep (~6 km) skarn-porphyry environment. Propylitic alteration assemblages were formed at lower temperatures (~380–420 °C) from a Ca-Na-chloride, low salinity (~8 wt% NaCl-eq.) magmatic-hydrothermal fluid. Fluid inclusions in minerals from phyllic alteration assemblages indicate the influx of a CO2-rich fluid at about 270–290 °C and 1400 ± 50 bars and subsequent mixing with more saline (20 wt% NaCl-eq.) and cooler (~240 °C) hydrothermal fluids.

Геохімія флюїдів: інноваційне вирішення фундаментальної проблеми

First of all, was developed a reliable mass spectrometric method for studying fluid inclusions in minerals (on the basis of the author’s certificate of the USSR No. 454446 of 1974 for the invention of the “device for cleaning the content inclusions of solid materials”). Were created and published new scientific directions: 1. Thermobarometry and geochemistry of gases of veinlet-impregnated mineralization in sediments of oil and gas regions and metallogenic provinces. 2. Bowels of the Earth – natural physicochemical reactor. Was developed a “method (technology) for determining the prospects of oil and gas bearing of the local area” and “a method (technology) of local forecasting of enriched areas of gold-ore fields” (together with M. M. Davydenko). Was established unknown before, but objectively existing phenomenon of the material world: 1) “lack of molecular hydrogen in inclusions in minerals in the bowels of the planet Earth” (together with V. A. Kaliuzhny). Independently were established: 2) previously unknown “property of deep abiogenic methane-termobar high-temperature fluid decompose-convert natural organic residues into layers of coal with their simultaneous methane saturation and its conservation in the earth’s crust of the planet Earth”; 3) previously unknown natural “phenomenon of arbitrary formation of natural carbon methane in the coal layers of the earth’s crust of the planet Earth under the influence of abiogenic methane-containing high-temperature fluid with their conservation in them”; 4) previously unknown different chemical properties of carbon isotopes in natural processes of synthesis-formation of various carbon-containing compounds ...; 5) “previously unknown pattern of natural processes of synthesis of perfect diamond crystals from astenospheric carbon dioxide ions...”. Was justified “a new way to determine the calorification of natural gas supplied to consumers and its cubic-metre barometry”.

Noble gas magmatic signature of the Andean Northern Volcanic Zone from fluid inclusions in minerals

Trace volatile elements like He are key for understanding the mantle source signature of magmas and to better constrain the relative roles of subduction and crustal processes to the variability of along-arc chemical and isotopic signatures of magmatic fluids. Here we report on noble gas abundances and isotopic data of Fluid Inclusions (FIs) in eruptive products and/or fumarolic gases from the Colombia-Ecuador segment of Andean Northern Volcanic Zone (NVZ). FIs in olivine phenocrysts from Ecuador (El Reventador, Cotopaxi and Tungurahua) yield air-normalized corrected 3He/4He ratios of 7.0–7.4 RA, within the MORB range (8 ± 1 RA). With exception of the Cotopaxi lavas (opx < <oliv.), these are indistinguishable of those obtained for their cogenetic orthopyroxene pairs and of gas emissions previously reported in literature. Olivine phenocrysts from Nevado del Ruiz fissure lavas also yield the highest 3He/4He (8.5 ± 0.3 RA) for this volcanic system, which is in the range of fumarolic gases for Galeras (previously reported as high as 8.8 RA and here measured to a maximum of 8.3 ± 0.1 RA). Our dataset highlights disparities between isotope signatures of eruptive products from Ecuador (avg. ~7.2 RA) and those reported for the Colombian portion of the NVZ (avg. ~8.5 RA). Previous studies on the geochemistry of erupted products put in evidence significant along-arc variations ascribed either to the involvement of different slab components, or to variable depths of evolution of arc magmas within the continental crust. However, the same variation is not discernible in the signature of noble gases, especially helium, from FIs and gas emissions analyzed in this study, with little inter-variation between Cotopaxi, Reventador and Tungurahua (all within 0.2 RA from the Ecuador average of 7.2) and Galeras and Nevado del Ruiz, whose maximum values differ by ~0.3 RA. We therefore suggest a homogenous MORB-like 3He/4He signature for the mantle wedge beneath this arc segment, whereby along-arc variations in crustal thickness (from <35 km at the northernmost part of the segment to ≥50 km at the Ecuadorian arc segment) may factor largely into the variability recorded on our data set. The first CO2/3He ratios obtained in FIs from Andean rocks support the hypothesis of increasing crustal contamination from Colombia to Ecuador, concomitant with increasing crustal thicknesses under the respective arc regions.

Ore-Forming Fluids of the Aleksandrovskoe and Davenda Deposits (Eastern Transbaikalia)

A study of the composition of fluid inclusions in ore minerals of the Davenda Mo–porphyry deposit and the Aleksandrovskoe sulfide–quartz–gold ore deposit, as well as of fluid inclusions in minerals of igneous rocks, showed that ore-forming fluids inherit the salt and gas composition of magmatic fluids generated during crystallization of ore-bearing rocks of the Amudzhikan–Sretensky Igneous Complex, which formed simultaneously with the Au and Mo mineralization. The gold-bearing sulfide–quartz veins of the Aleksandrovskoe deposit formed with the participation of two types of hydrothermal fluids, differing in the composition of salts and the gas phase: homogeneous Ca–Na chloride fluids with CO2 and heterophasic Na–K–Fe-chloride fluids, which indicates two sources of ore-forming fluids during the formation of Au-mineralization. Na–K–Fe-chloride fluids in terms of salt and gas composition were similar to the ore-forming fluids of the Mo-mineralization of the Davenda deposit. Ore-forming Ca–Na-chloride with CO2 The fluids of the Aleksandrovskoe field are comparable in salt and gas composition with the magmatogenic fluids of quartz diorite porphyries and diorite porphyrites. Ore forming Na–K–Fe carbonate-chloride fluids of the Davenda and Aleksandrovskoe deposits show great similarity in composition to magmatic fluids of granite porphyry and emphasize the genetic identity of Mo mineralization in both deposits. The data obtained confirm the widespread opinion that a genetic relationship exists between gold mineralization and dikes of intermediate and mafic composition, and molybdenum–porphyry mineralization with granite–porphyry of the Amudzhikan–Sretensky Igneous Complex. The real agents of this genetic link are metalliferous magmatogenic fluids, the salt and gas composition of which inherit ore-forming fluids. The formation depth of productive ore mineral assemblages in veins of the Aleksandrovskoe and Davenda deposits is estimated at 7.9–7 and 8–6.3 km, respectively, which is not typical of porphyry deposits, the formation of which is characterized by shallower depths.

АЛЕКСАНДРОВСКОЕ ЗОЛОТОРУДНОЕ МЕСТОРОЖДЕНИЕ (ВОСТОЧНОЕ ЗАБАЙКАЛЬЕ): ИСТОЧНИКИВЕЩЕСТВА ПОРОД И РУД

Актуальность исследованиясостоит в необходимости расширения минеральной сырьевой базы России. Восточное Забайкалье является одним из старейших золотодобывающих регионов страны. Тем не менее даже в таком хорошо изученном регионе остро стоит вопрос о поисках и обнаружении новых рудных месторождений. Для успешного выполнения такой задачи необходимы данные детального изучения уже известных рудных месторождений, которые могут быть использованы для разработки научно обоснованных критериев поиска рудных месторождений и прогноза оруденения. К таким данным относится определение источников рудоносных магматических расплавов, возраста и условий формирования золотого оруденения Александровского месторождения. Целью исследования является доказательство участия в рудообразовании нескольких магматических очагов с разными характеристиками на основании результатов изучения особенностей распределения редкоземельных элементов в магматических породах и рудах, изотопного состава кислорода рудоносного кварца и серы сульфидов, а также выявление физико-химических условий формирования оруденения с помощью исследования флюидных включений в минералах. Объектом исследования является Александровское золоторудное месторождение, расположенное в Восточном Забайкалье. Методы. Для определения элементного состав пород использовался рентгенфлуоресцентный метод и стандартный химический анализ, концентрации редкоземельных элементов измерялисьсорбционно-атомно-эмиссионным анализом с индуктивно-связанной плазмой (ГИН СО РАН, г. Улан-Удэ). Изучение изотопного состава серы сульфидов, содержаний Au и Ag, изотопного возраста (40Ar/39Ar) проведено в Центре коллективного пользования многоэлементных и изотопных исследований СО РАН (г. Новосибирск). Флюидные включения в кварце рудных жил изучены традиционными методами термобарогеохимии и методом КР-спектроскопии. Результаты. Определен возраст (40Ar/39Ar) синрудного серицита (162 ±2,3 млн лет), соответствующий возрасту интрузий амуджикано-шахтаминского комплекса. Установлено, что вариации изотопного состава кислорода рудоносного кварца, изотопов серы сульфидов соответствуют флюиду магматической природы. Анализ распределения редких и редкоземельных элементов указывает на то, что источниками оруденения были разноглубинные, в разной степени дифференцированные магматические очаги, функционировавшие как в верхней, так и в нижней континентальной коре. По данным исследования флюидных включений в кварце рудных жил, кристаллизация минеральных парагенезисов руд месторождения происходила в интервале температур от 150 до 402°С. Продуктивная минеральная ассоциация формировалась при температуре 402–360°С. Установлено участие в процессе рудообразования рудообразующих флюидов, различающихся по солевому составу, что указывает на разные условия генерации и природу рудообразующих флюидов. Отличительной особенностью месторождения является образование руд за счет разноглубинных, в разной степени дифференцированных рудоносных магматических источников.

Stability of copper acetate at high P-T and the role of organic acids and CO2 in metallic mineralization

Many metal deposits were formed by carbonic fluids (rich in CO2) as indicated by fluid inclusions in minerals, but the precise role of CO2 in metal mineralization remains unclear. The main components in fluid inclusions, i.e. H2O and CO2, correspond to the decomposed products of organic acids, which lead us to consider that in the mineralization process the organic acids transport and then discharge metals when they are stable and unstable, respectively. Here we show that the thermal stability of copper acetate solution at 15–350 °C (0.1–830 MPa) provides insight as to the role of organic acids in metal transport. Results show that the copper acetate solution is stable at high P-T conditions under low geothermal gradient of <19 °C/km, with an isochore of P = 1.89 T + 128.58, verifying the possibility of copper transportation as acetate solution. Increasing geothermal gradient leads to thermal dissociation of copper acetate in the way of 4Cu(CH3 COO)2 + 2H2O = 4Cu + 2CO2 + 7CH3COOH. The experimental results and inferences in this contribution agree well with the frequently observed fluid inclusions and wall-rock alterations of carbonate, sericite and quartz in hydrothermal deposits, and provide a new dimension in the understanding of the role of CO2 during mineralization.

Physico-chemical modeling of hidrothermal mineralization processes at Ni-Co-As (± U-Ag), Co-S-As (± Au-W), Cu-Co-As (± Sb-Ag) deposits.

A generalization of the results of the study of the composition of metal-bearing fluids of cobalt deposits of hydrothermal Genesis, formed in different geodynamic settings in connection with the formation of alkaline and alkaline-basite intrusions and dikes. To determine the physical and chemical parameters of ore deposition from fluid inclusions in minerals, both traditional and new instrumental methods of thermobarogeochemistry were used: thermo-and cryometry, RAMAN spectroscopy, concentration of ore and petrogenic elements in individual fluid inclusions were evaluated by LA-ICP-MS. The obtained results served as the basis for the study, the main task of which was the thermodynamic modeling of the conditions of joint transport and deposition of Co, Ni, Cu, Fe, Mg, Ca, Ag, Au, Bi, U, Pt and Pd C calculation of a number of equilibrium States of the hydrothermal system, the composition close to the natural ore-forming fluids. Physical and chemical factors of native deposits-gold, silver, platinum and palladium in the ores of such deposits are revealed. The obtained data can serve as a basis for the development of correct genetic models of ore-forming systems of cobalt deposits and contribute to solving the problems of their search.