Mineral Inclusions Research Articles

Evolution of the Hydrothermal Fluids Inferred from the Occurrence and Isotope Characteristics of the Carbonate Minerals at the Pogo Gold Deposit, Alaska, USA

Pogo is identified as a deep-seated, intrusion-related gold deposit. Carbonate minerals have a close spatial relationship to hydrothermal gold mineralization in all of its principal ore zones. The carbon and oxygen isotopic ratios of carbonate minerals (siderite, ankerite, and calcite) present within the deposit illustrate the isotopic evolution of the ore-forming fluid. The initial hydrothermal fluid phase is interpreted to be magmatic in origin. The fluid evolution was characterized by a gradual decrease in δ18O and a slight increase in δ13C with decreasing temperature. The dominant carbon-bearing species was CO2, with methane introduced sporadically. Siderite is associated with early-stage mineralization and occurs with ankerite in main-stage ore assemblages. Calcite is recognized in the later stages of mineralization. Gold in the Pogo deposit occurs as native gold, Au-Bi-Te minerals, inclusions in sulfide minerals, or as “invisible gold”. The latter is found in pyrite, chalcopyrite, arsenopyrite, and quartz, based on ion microprobe analysis. The presence of invisible gold in these minerals has significant metallurgical implications for gold processing at the Pogo mine.

Origin of the Miaoling Gold Deposit, Xiong’ershan District, China: Findings Based on the Trace Element Characteristics and Sulfur Isotope Compositions of Pyrite

The Xiong’ershan district is situated on the southern margin of the North China Craton (NCC) and located within the Qinling–Dabieshan Orogen’s orogenic zone. It is adjacent to the XiaoQinling mining district and exhibits very favorable geological conditions for mineralization, as the district contains numerous gold deposits, positioning it as one of the key gold-producing areas of China. The Miaoling gold deposit is a hydrothermal deposit and is controlled by the Mesozoic nearly NS-trending fault. The ore bodies are hosted in the Mesoproterozoic Xiong’er Group of the Changcheng System of volcanic rocks, with reserves reaching large-scale levels. Pyrite is the main gold-bearing mineral and can be classified into four generations: early-stage fine- to medium-grained euhedral to subhedral cubic pyrite (Py1); medium- to coarse-grained euhedral to subhedral cubic granular pyrite in quartz veins (Py2a); fine-grained subhedral to anhedral disseminated pyrite in altered rocks (Py2b); and late-stage anhedral granular and fine-veinlet pyrite in later quartz veins (Py3). Through in situ trace element analysis of the pyrite using LA-ICP-MS, a positive correlation between Au and As was observed during the main mineralization stage; gold mainly exists as a solid solution within the pyrite lattice, and the ablation signal curve reflecting the intensity of trace element signals showed that gold also occurs as micron-scale mineral inclusions. The trace element content suggested a gradual increase in oxygen fugacity from Stage 1 to Stage 2, followed by a decrease from Stage 2 to Stage 3. The Co/Ni values in the pyrite (0.56 to 62.02, with an average of 12.34) exhibited characteristics of magmatic hydrothermal pyrite. The in situ sulfur isotope analysis of the pyrite using LA-MC-ICP-MS showed δ34S values of 4.24‰ for Stage 1, −6.63‰ to −13.79‰ for Stage 2, and −4.31‰ to −5.15‰ for Stage 3. Considering sulfur isotope fractionation, the δ34S value of the hydrothermal fluid during the main mineralization stage was calculated to be between 0.31‰ and 2.68‰.

Mineral inclusions in the accretion ice above Lake Vostok

The paper is based on additional studies of mineral inclusions in the accretion ice sampled by deep drilling at Vostok Station in central Antarctica. The studies include X-ray microtomography of two mineral inclusions with identification of their mineral composition; analysis of clay minerals in the soft aggregate of the largest inclusion; and geochronological study of zircon grains. X-ray microtomography shows intact morphology of the inclusions in the ice core and their internal texture. The soft aggregate of the largest inclusion is characterized by the dominance of illite, intermediate concentrations of chlorite and small amounts of kaolinite. A notable feature is the absence of mixed-layer minerals typical of Antarctic coastal areas. The most valuable information is derived from new geochronological data and their integration with previous dating data. The detrital zircon U-Pb ages show strong probability peaks between 900 and 1100 Ma, while the detrital monazite ages are clustered between 1250 and 1450 Ma. Both of these age intervals correspond to the Rayner Orogeny.

Mineralogy and primary sources of gold in Davenda-Klyuchevsky ore-placer cluster (Eastern Transbaikalia)

The Davenda-Klyuchevsky ore cluster contains a large number of gold placers and ore occurrences, deposits of gold-sulfide-quartz and gold-bearing Mo-porphyry formations of stockwork and vein types. Judging by the morphology of gold, most placers are closely spatially related to ore sources, but data on the chemical composition of gold from placers and ores are very limited in the literature. A detailed mineralogical and geochemical study of placer gold, which is the subject of this work, provides important genetic information that can be used to predict and search for gold mineralization. It has been established that the fineness of placer gold is well comparable to the fineness of ore gold. In the autochthonous placers, that formed a distant aureole around the Klyuchevskoye deposit, are dominated by gold with a fineness of 900–950‰. Gold often contains inclusions of ore minerals and forms intergrowths with them. First of all, these are pyrite, galena and Bi minerals (tetradymite, Bi tellurides, Bi-containing sulfosalts, native Bi, bismuthine), less often – arsenopyrite, chalcopyrite, fahlores. In the autochthonous placers, located around the Davenda deposit, gold with a fineness of more than 950‰ predominates; inclusions of ore minerals (pyrite, galena, tetradymite, PbBiCuS mineral, arsenopyrite) in the gold of these placers are rare. The third type of gold (850–900‰) is less common in the above-mentioned placers, but predominates in the autochthonous placers of the Maly and Levy Amundzhikan rivers. In essentially allochthonous placers on the periphery of the Davenda-Klyuchevsky ore cluster and the Cherny Uryum River, lower grade gold is also common. In this group of placers, the mineral association of Au changes somewhat. Galena and Bi minerals are almost never found together in gold grains; hessite, acanthite, and petzite appear, associated with Bi minerals or pyrite. The heavy concentrates contain cinnabar. The fineness of placer gold and its associations with ore and nonmetallic minerals indicate telescoping mineralization in ore sources and the superimposed nature of placer-forming gold mineralization.

Raman scattering of omphacite at high pressure: Toward its possible application to elastic geothermobarometry

Abstract Due to their widespread occurrence in several geological settings, omphacite inclusions could be used for elastic Raman geothermobarometry. However, the Raman scattering of complex silicate minerals entrapped in a host depends on both the chemical composition and elastic strain developed during the metamorphic pathway, which makes the task very challenging. Here, as a very first step to probe the potential of omphacite to be used as a mineral inclusion in elastic geothermobarometry, we report the pressure dependence of the Raman spectra of omphacite crystals with the same composition, approximately Jd43Di57, but having different symmetry because of the existence (P2/n) or absence (C2/c) of chemical order at the six- and eight-coordinated cation sites. The experimental results are complemented by ab initio quantum mechanical simulations on fully ordered omphacite (Jd50Di50). We demonstrate that the position of the well-resolved Raman peak near 688 cm–1, arising from Si-O-Si bond bending, is very sensitive to pressure but independent of the state of chemical order, which makes it promising to be utilized in Raman geobarometry. The width of this peak varies with chemical order but not with pressure and therefore can be used to constrain the temperature of inclusion entrapment, because the chemical order is indicative of the closure temperature of the cation-exchange reaction. However, further detailed analyses on the compositional variation of the Raman spectra of omphacite is required before considering omphacite-in-garnet systems to be suitable for Raman elastic geothermobarometry.

Distribution of tellurium, selenium, cobalt and gold in sulfide minerals: A case study of the Jiguanzui porphyry-skarn Au-Cu deposit, eastern China

The Jiguanzui deposit is a representative porphyry-skarn Au-Cu deposit in the Mid-Lower Yangtze River metallogenic belt, Eastern China, characterized by significant critical metal (Te, Se, Co) association. Previous study focused on the Te and Se distribution in the ores and pyrite minerals on deposit scale, this study present trace element geochemistry of various sulfide minerals (chalcopyrite, bornite, sphalerite, molybdenite) through LA-ICP-MS analysis, aiming to reveal the distribution of Te, Se, Co, and Au among sulfide minerals in this deposit. Except molybdenite, which host high concentrations of Te and Se, pyrite and chalcopyrite generally have higher Te contents than bornite and sphalerite, whereas bornite and chalcopyrite exhibited relatively high Se concentrations. Cobalt and Au are dominantly hosted in the pyrite and chalcopyrite, respectively, although the highest Au concentration up to 14 ppm was analyzed in pyrite. Principal component analysis of trace element contents and time-resolved LA-ICP-MS signal depth profiles indicate that Te occurred as Te-Ag minerals and mineral inclusions within the sulfides, whereas Se and Co are incorporated into the lattices of sulfide minerals. Principal component analysis of trace element contents in various sulfides exhibit intimate Pb-Bi-(Cu)-Au associations, suggesting that Au is present as tiny mineral inclusions coexisting with either Cu-Bi sulfosalts or Pb sulfides or sulfosalts. This case study also highlights that Te and Se hosted in pyrite are not recoverable with current recycling technologies.

Efficacy analysis of electroacupuncture plus TDP in the treatment of peripheral facial paralysis: a systematic review and meta-analysis.

This study intends to carry out a systematic review and meta-analysis of electroacupuncture combined with TDP in the treatment of peripheral facial paralysis. CNKI, VIP, Wanfang, PubMed, Embase and Cochrane databases were searched for literatures on randomized or quasi-randomized controlled trials of electroacupuncture combined with TDP in the treatment of peripheral facial paralysis, and the references of the included studies were searched. Meta-analysis was performed using Stata15.0 software after risk of bias, quality assessment, and data extraction of the included articles by two reviewers independently. Fifteen articles were finally included, with approximately 1,568 participants (920 in the treatment group and 648 in the control group). Meta-analysis showed that the effective rate of electroacupuncture combined with TDP in the treatment of peripheral facial paralysis was not significantly different from other treatment methods ([RR = 1.05, 95%CI (0.97, 1.12), p = 0.226]), and the recovery rate was better than other treatment methods ([RR = 1.14, 95%CI (1.05, 1.24), p = 0.002]). Subgroup analysis showed that when stratified by the inclusion of minors in the study population, it was observed that in studies including minors, the combination of electroacupuncture and TDP therapy demonstrated superior efficacy in treating peripheral facial paralysis compared to other therapeutic modalities [OR = 1.14, 95% CI (1.03, 1.25), p = 0.011]. Conversely, in studies where the population comprised solely adults, no significant difference was found between the combination therapy and other treatments [OR = 1.15, 95% CI (0.99, 1.33), p = 0.059]; whether electroacupuncture alone or other treatment methods, the recovery rate of electroacupuncture combined with TDP in the treatment of peripheral facial paralysis was better than other methods. Electroacupuncture combined with TDP is superior to other treatment methods in the treatment of peripheral facial paralysis.

Allies or foes? Does the inclusion of new minorities undermine or strengthen the European system of minority protection?

AbstractThis article analyses how the European minority rights system can be applied to migrant communities, and what implications such an extension of the scope of the system might have for the preservation of minority identities and the integration of European societies. Currently, most European states rely on an artificial distinction between old and new minorities, which is becoming untenable in practice. Therefore the article assesses three options of how recently arrived migrants can be incorporated into the European minority rights system: 1. maintaining the existing separation of old and new minorities, which does not promote the rights of migrant communities and is also not the most effective for integration; 2. incorporating migrant communities to the existing European system of minority rights, which provides little benefit to migrant communities and also has the potential to decrease the protection provided to autochthonous minorities; and 3. redesigning the system by including all minorities, but differentiating in the content of rights. The article argues that under the third approach, integration is possible without giving up minority languages and other essential characteristics of migrant communities' culture. It is therefore possible and desirable to extend the European minority rights system to recently arrived migrant communities.

Geochemical Characteristics of Melts from the Eastern Volcanic Belt and Sredinny Range of Kamchatka: Analysis of Evidence from Melt Inclusions

We analyzed sets of published data on the composition of glasses from melt inclusions in minerals of volcanics from the Eastern Volcanic Front and Sredinny Range of Kamchatka. A significant difference was revealed between the distribution of silica contents in the rocks and melts: intermediate compositions are most common among the rocks, whereas the melts are dominantly silicic. The distribution of major and trace element was analyzed. It was shown that the contents of some elements are environment-specific (e. g., Nb and light REE). We distinguished trace element ratios in melts that most strongly correlate with the geodynamic setting.

Exploring of the suitability of garnets for immobilizing nuclear waste and radiation shielding

In this study, the structural, chemical composition and gamma and nuclear shielding properties of some garnets were investigated. The experimental studies were made on the mass attenuation coefficients (MAC), linear attenuation coefficients (LAC), mean free path (MFP), half-value layer (HVL), effective atomic numbers (Zeff) and the radiation protection efficiency (RPE) in the high energy region. The fast neutron removal cross sections (ΣR), exposure buildup factors (EBF) were theoretically determined. The neutron absorption equivalent dose was measured of the garnet by 241Am–Be fast neutron source. It may be concluded that P1.21 has better photon shielding than the other samples investigated. The equivalent dose rate absorbed by the P1.21 garnet sample was found to be 36.80 % μSv/h and the P1.21 sample shows promise as a neutron shielding option. Also, the detection of inclusion minerals were made by EPMA and SEM analysis. It is observed that P1.21 sample is pyrope, P1.3 sample is andradite and P1.6 sample is grossular series. Also, according to ICP-MS results, it is possible to say that the P1.21 sample, which contains high amount of uranium, thorium, Y and Zr and has a high radiation absorption capacity, is a potential garnet structure for nuclear waste immobilization. Garnet's crystal structure and chemical durability enable safe containment and long-term storage of radioactive elements, facilitating their secure disposal.

Implications for metallogenic evolution of the Balong gold deposit, East Kunlun metallogenic belt: Insights from in-situ trace elements and S isotopes of sulfides

The Balong gold deposit is one of numerous lode gold deposits in the East Kunlun metallogenic belt. Gold mineralization is hosted in Triassic granitoids, typified by auriferous quartz veins. Hydrothermal alteration includes sericite, quartz, sulfide, chlorite, and calcite. Pyrite, as the most abundant sulfide in the ore, is sometimes seen in the company of arsenopyrite. Three types of pyrite have been identified. The porous Py1 exhibits low Co and Ni contents, with an absence of gold. Subhedral Py2-1 shows higher Co (median 80 ppm) and Ni (median 10.5 ppm) contents and contains various Cu-Pb-Zn-Ag mineral inclusions. Py2-2 shows an increase in As (median 17, 073 ppm) and Au (median 3.79 ppm), exhibiting obvious distinctions between Py2-1 and Py2-2.Gold in the Balong deposit consists of both visible and invisible gold. Gold occurs within micro-fractures of pyrite and arsenopyrite, appearing as irregular inclusions or as infillings. Apart from visible gold grains, the majority of invisible gold hosted in Py2-2 occurs as solid solutions (Au+). Coupled dissolution-reprecipitation reactions of early pyrite are a key factor for visible gold precipitation and later invisible gold enrichment. Pyrite records a narrow range of δ34S values from −1.6 to 5.4 ‰, reflecting sulfur from a deep magmatic source. These findings indicate a connection between the ore-forming materials and the evolved magmatic-hydrothermal fluids.

Anisotropic induced polarization modeling with neural networks and effective medium theory

Interpreting three-dimensional induced polarization (IP) data requires rock physics models that reflect the omnipresent anisotropy of the Earth’s crust. The Generalized Effective Medium Theory of Induced Polarization (GEMTIP) can model the IP signatures of rocks with polarizable mineral inclusions. However, it is computationally demanding because it requires numerically solving the depolarization tensors of each inclusion. We aim to streamline GEMTIP simulations by (1) integrating anisotropic background conductivity and triaxial ellipsoidal inclusions in the model and (2) estimating the depolarization tensors with a neural network. We validate the neural network predictions against known solutions for spherical and spheroidal inclusions, and we test our method using data from an actual rock sample. The neural network shows a relative sensitivity of 56% to inclusion shape and 44% to host rock anisotropy and is up to 100,000 times faster than numerical integration. We release the pre-trained neural network implementation as an open-source Python package, thereby providing a new method to interpret the IP signatures of anisotropic rocks.

The fluid/melt partitioning of chlorine, bromine and iodine in felsic magmas and the utility of halogen ratios to track the devolatilization and fluid fluxing of magma reservoirs

The release of fluids from magmas at crustal depths is an essential process for the formation of magmatic-hydrothermal ore deposits. However, assessing the extent of volatile loss by magma degassing or volatile gain by fluid fluxing from deeper magmas remains challenging. To develop a new tool to quantitatively track these processes, we experimentally determined the partition coefficients of Cl, Br, and I between aqueous fluids and haplogranitic melts (Dif/m) as a function of fluid salinity and the aluminum saturation index [ASI = Al2O3/(Na2O + K2O)] of the silicate melt. The experiments were conducted in externally heated rapid-quench René 41 cold-seal pressure vessel apparatus at 200 MPa and 790 ± 10 °C. The Br and I concentrations in the run product glasses were determined by laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectrometry, whereas the concentration of Cl was determined by electron probe microanalysis. The results show that the partition coefficients of the three halogens in a system with chloride-dominated fluids increase with fluid salinity increasing from 1.49 to 60.6 wt% total NaCl equivalent. Specifically, DClf/m increases from 23 ± 5 to 168 ± 7 (1σ), DBrf/m increases from 57 ± 13 to 271 ± 14, and DIf/m increases from 198 ± 61 to 736 ± 159. As for the influence of melt composition, DClf/m and DBrf/m attain maximum values at ASI = 1, whereas DIf/m appears to be independent of ASI within error. Bromine and iodine partition into the fluid more strongly in the presence of significant Cl, indicating that these halogens compete for the same structural sites in the silicate melt. Empirical equations were derived to predict the Df/m of Cl, Br, and I in felsic magmatic systems as a function of fluid salinity and silicate melt ASI. These equations were in turn implemented in numerical models simulating the degassing of granitic magma reservoirs emplaced in the Earth’s upper crust. The results of these calculations show that the Br/Cl and I/Cl ratios in the silicate melt and the released fluid rapidly decrease during progressive magma degassing at depth due to the significantly increasing fluid/melt partition coefficients with increasing halide ion radius. On the other hand, a sudden increase of Br/Cl and I/Cl in the silicate melt indicates fluid fluxing of the magma. Therefore, halogen ratios may become particularly useful tools to track crystallization-driven degassing if the record of the variation of the silicate melt composition can be recovered from silicate melt inclusions in minerals. In addition, the evolving Br/Cl and I/Cl ratios of magmatic fluids feeding magmatic-hydrothermal ore forming systems, as recorded by fluid inclusions in minerals, may inform about the evolution of the underlying magma reservoir.

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.

Nonbinary youth and young adult experiences in organized team sports in Canada

Research concerning sexual and gender minority inclusion in sport has primarily focused on cisgender and binary transgender participants. Participation in organized team sport among nonbinary people is understudied. The goal of this study was to identify the barriers nonbinary people face to entering and remaining in organized team sports in Canada. The Understanding Affirming Communities, Relationships and Networks Study surveyed 6495 15-29-year-olds in Canada, including 2513 nonbinary (encompassing genderqueer, agender, third gender and trans nonbinary) and 1929 cisgender respondents. A smaller proportion of nonbinary respondents (11%) participated in team sport compared to cisgender respondents (18%) (p = 0.001). More nonbinary respondents (62%) have played a sport and then stopped compared to cisgender respondents (57%) (p = 0.0008). The most commonly reported reason nonbinary people felt unsafe in sport was discriminatory comments, with >50% witnessing homophobic, transphobic, and/or sexist comments. Structural and policy changes by organizers, administrators, and coaches can support the inclusion of nonbinary people in organized team sports.

Petrological characterization for material provenance of haniwa earthenware from mounded tombs in the Kibi region, Japan

To determine the provenance of the materials used in the production of haniwa earthenware unearthed from mounded tombs (kofun) in the Kibi region (modern Okayama Prefecture) during the Kofun period (late 3rd – 6th century CE) of Japan, we carried out petrological analyses of haniwa sherds, including optical microscopy, X-ray diffractometry, X-ray fluorescence spectroscopy, and electron-probe analysis. The 25 haniwa sherds analyzed from 12 representative mounded tombs are composed of mineral and rock inclusions with variable grain size set in a clay matrix. The dominant inclusions are quartz, K-feldspar, and plagioclase, associated with minor amounts of amphibole, volcanic glass, and granitic rocks in all the haniwa sherds, and small amounts of hornfels, quartz rock, and accessory minerals, including mica, ilmenite, and chromite, in some of the sherds. Amphibole and plagioclase have compositional variations indicative of the mixing of tephra and granitic components. The compositions of volcanic glass inclusions are similar to those of the Aira-Tanzawa and Kikai-Akahoya tephras widely distributed in southwestern Japan. Bulk chemical compositions show magmatic differentiation trends, which are variable between individual tombs. From these results, it is concluded that the paste materials of haniwa in the Kibi region were commonly derived from weathered granitic rocks mixed with minor amounts of three widespread tephras. The variations of chemical and mineralogical compositions are probably the reflection of local geologic settings, suggesting the presence of specific mining sites of paste materials around each tomb. The mining sites could be located at the bases of hills of granitic rocks covered by widespread tephras and in some cases, near the flood plain of big river systems.

Combined study of Au-bearing arsenopyrite of orogenic gold deposits (NE Asia): High resolution 3D X-ray computed tomography, LA-ICP-MS, and EMPA data

The distribution of gold in small acicular arsenopyrite of a pyrite-arsenopyrite association from Suzdal (Eastern Kazakhstan), Olympiada (Yenisei Ridge, Russia) and large pseudorhombic arsenopyrite crystals from Bazovskoe (Yakutia, Russia) orogenic-type deposits were investigated. On orogenic gold deposits in NE Asia, occurring mainly in black shales, two productive stages of ore deposition are distinguished, which correspond to two morphological varieties of arsenopyrite. At the early stage, fine-grained acicular-prismatic arsenopyrite with invisible gold was deposited; at the late stage, tabular arsenopyrite in association with free visible gold was formed. The samples of gold-bearing arsenopyrite were analyzed using Scanning Electron Microscopy, Electron Microprobe Analyses, Atomic Absorption and Laser Ablation Inductively Coupled Plasma Mass Spectrometry in combination with High Resolution 3D X-ray Computed Tomography (HRXCT). HRXCT does not destroy the studied mineral during the investigation. That technique permits to do an estimation of the amount of gold inclusions in minerals or host rocks and draw reasonable conclusions about the gold content of the ores, to study in detail the distribution patterns of metal inclusions (associated with certain minerals, cracks, crystal growth faces, etc.) and to determine the form of the gold. It can be used to understanding of the genesis of productive mineral associations, and to developing optimal technological schemes for gold extraction.

EVIDENCE OF EXTREME REDOX VARIATIONS IN SUBDUCTION-ZONE DIAMOND

The article presents new data on multiphase inclusions in two diamonds sampled from placers in the northeastern Siberian craton. Diamond HLS-4 is a round variety V crystal containing a multiphase mineral inclusion with more or less strongly oxidized iron carbides and moissanite in one part and calcite and iron oxides in another part. Another sample, HI-180, is a partly dissolved yellow cuboid that hosts a multiphase inclusion and numerous submicrometer inclusions delineating the crystal zoning. Sample HI-180 is deformed, with cracks and cavities up to 200 μm in size exposed in a polished section. The submicrometer inclusions plot in the field of microinclusions in fibrous diamonds from the world database, mostly near the silicic corner. They must have a hydrous composition, judging by the water-carbonate ratio of H2O/(H2O + CO2) = 0.80–0.82 estimated from FTIR data. The multiphase inclusion consists of quartz, Fe-armalcolite, anatase, and diamond grains in an amorphous matrix, as well as moissanite and calcite detected by SEM-EDS, FTIR and Raman spectroscopy. One diamond grain in the inclusion, in turn, encloses moissanite. The coexistence of calcite and moissanite in multiphase inclusions is evidence that cracks were fully healed up under extreme redox variations, possibly, during diamond growth in a subduction setting.

Composition of Gases in the Interporous Space of Technogenic Bodies

Abstract —We present results of studies of inclusions in secondary sulfates (antlerite and a mixture of copiapite and coquimbite) and arsenates (erythrite and picropharmacolite) formed on the surface of technogenic bodies, such as stored waste from the enrichment of sulfide (Belovo and Ursk waste heaps) and arsenide (disposal maps of the Tuvakobalt plant) ores. A wide range of components were identified in the gas–liquid inclusions, the main ones being water and carbon dioxide. Hydrocarbons, oxygen-containing organic compounds, and nitrogen- and sulfur-containing gases were found in smaller but measurable amounts. Arsine H3As was also detected in inclusions in picropharmacolite (calcium and magnesium arsenate–arsenite). The gas–liquid inclusions in secondary minerals reflect the composition of the interporous space in the waste body, filled with particular atmospheric gases entering the body in free form and with seasonal precipitation. The combination of in situ generated and penetrating gases determines the diversity of inorganic and biotic interactions in technogenic bodies. The presence of hydrocarbons and oxygen-containing organic compounds is, most likely, associated with bacterial transformations of organic matter (residual vegetation, wood, microalgae, and fungi). At the same time, carbon disulfide and sulfur dioxide are indicators of active inorganic reactions of decomposition of the sulfide matrix.

Fluid inclusions and H–O isotopes of the super-large Nanyangtian tungsten deposit in southeastern Yunnan, southwestern China

The Nanyangtian deposit is a super-large reduced skarn tungsten deposit located in the Laojunshan WSn polymetallic ore province in southeastern Yunnan (SW China). The deposit is represented by three flat-lying mineralized zones formed vertically by the replacement of limestone or minor calcareous schist. The tungsten orebodies are mainly stratiform, lenticular, and vein types, hosted in the Paleoproterozoic Nanyangtian Formation. Three mineral formation stages have been identified based on the mineral assemblages and vein crosscutting relationships (pre-, syn-, and post-ore). The Nanyangtian is a calcic skarn deposit, dominated by a grossular-diopside-tremolite-actinolite assemblage. Scheelite, pyrrhotite, pyrite, and chalcopyrite are the main ore minerals. Detailed petrographic observations show three types of fluid inclusions (FIs) in various hydrothermal minerals: liquid-rich two-phase (type-I), gas-rich two-phase (type-II), daughter mineral-bearing three-phase (type-III). Their homogenization temperatures (193–298 °C) and salinities (1.2–9.3 wt% NaCl eq.) indicate that the Nanyangtian ore-forming fluids were of medium to low temperature and low salinity compared to the statistical data from representative skarn tungsten deposits in South China. Laser Raman microprobe analysis of the FIs shows that the inclusions are dominated by H2O with minor CH4 and N2. The δD values (relative to Vienna-Standard Mean Ocean Water, VSMOW) of fluid inclusions and calculated δ18Owater values (relative to VSMOW) of the fluids in equilibrium with hydrothermal minerals are −105 to −69 ‰ and − 1.9 to 7.6 ‰, respectively. These oxygen–hydrogen isotopic compositions indicate that the ore-forming fluids were magmatic-derived, which may have metasomatized the Nanyangtian Formation carbonaceous calcareous rocks along interlayer structures to form the prograde skarn minerals. Then the fluids mixed with meteoric water migrated along faults to form the retrograde skarn and tungsten ore. Mixing of magmatic fluid with meteoric water is likely the main factor for the ore precipitation at Nanyangtian.