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The genesis of the subduction mélange in the central Qiangtang terrane has been a long hot debate. However, little research has been conducted on the brittle failure within the accretionary wedge, which is very important to unveil the structural evolution of the mélange. In this study, based on the recognition of multiple deformational phases, we analyse the characteristics and formation history of the vein system in the Gangma Co mélange. Six groups of quartz veins are recognized. Foliation‐parallel extension veins (G1 veins), shear veins (G2 veins) and foliation‐perpendicular extension veins (G4 veins) are supposed to have formed during the subduction of oceanic crust, recording the repeated low‐angle thrust‐sense frictional sliding, tensile fracturing and stress changes generated by subduction‐related earthquakes. Subsequent vertical extension veins (G5 veins) are suggested to be related to the exhumation of the underplated mélange, while the horizontal extension veins (G6 veins) in the last phase represent the final horizontal thrusting. The temperature conditions for shear vein formation were examined by fluid inclusion analysis, ranging from 120 to 200°C, coinciding with the temperature conditions of the slow earthquake region where episodic tremors and slow slip occur. This contribution supports that the Gangma Co mélange represents an in situ subduction zone and that its internal vein system is a response to the tectonic evolution of the Longmu Co‐Shuanghu Tethys Ocean. [ABSTRACT FROM AUTHOR]

Hypogene dissolution‐precipitation processes strongly affect the petrophysical properties of carbonate rocks and fluid migration pathways in sedimentary basins. In many deep carbonate reservoirs, hypogene cavernous voids are often associated with silicified horizons. The diagenesis of silica in carbonate sequences is still a poorly‐investigated research topic. Studies exploring the complexity of silica dissolution‐precipitation patterns in hypogene cave analogues are therefore fundamental to unravel the diagenetic and speleogenetic processes that may affect this kind of reservoir. In this work, we investigated an exhumed and silicified Neoproterozoic carbonate sequence in Brazil hosting a 1.4 km‐long cave. Quartz mineralization and silicified textures were analyzed with a multidisciplinary approach combining petrography, fluid inclusion microthermometry, silicon‐oxygen stable isotope analyses and U‐Th‐Pb dating of monazite crystals. We found that an early silicification event caused the replacement of the dolostone layers with micro‐crystalline quartz forming chert nodules. This event was likely associated with mixing fluids (ancient Neoproterozoic seawater and hydrothermal solutions sourced from the underlying Mesoproterozoic basement) at relatively low temperatures (ca. 50–100°C) and shallow depth. After the tectonic deformation produced by the Brasiliano orogeny, silica dissolution was promoted by high temperature and alkaline hydrothermal solutions rising from the quartzite basement along deep‐rooted structures. Hypogene hydrothermal alteration promoted the dissolution of the cherty layers and the precipitation of chalcedony and megaquartz. Homogenization temperatures from primary fluid inclusions in megaquartz cement indicate minimum formation temperatures of 165–210°C. Similar temperature estimates (110–200°C) were obtained from the δ30Si and δ18O isotope systematics of quartz precipitated from hydrothermal solutions. The dissolved salts in the fluid inclusions were evaluated as NaCl + CaCl2 from microthermometric data combined with cryogenic Raman spectroscopy, corresponding to salinity ranging between 17 and 25 wt.%. No reliable age constraints for hydrothermal silica dissolution‐precipitation phases were obtained from monazite U‐Th‐Pb dating. However, our results, interpreted in the regional context of the São Francisco Craton, suggest that the Cambrian tectono‐thermal events could have been amongst the possible drivers for this hypogene process in the basin. [ABSTRACT FROM AUTHOR]

The Tertiary‐Piedmont Basin (NW Italy) is an episutural basin that developed from the late Eocene on the Alps–Apennines tectonic junction. Several coeval geodynamic processes, including the loading and exhumation of the Western Alps, the outward migration of the Apennine accretionary wedge and the opening of the Liguro‐Provençal rift basin, controlled the basin evolution. We integrate fluid‐inclusion microthermometry, low‐temperature thermochronology and burial history with numerical modelling to constrain the palaeo‐geothermal gradients required and evaluate the mechanisms that governed the basin thermal history. Apatite fission‐track and (U‐Th‐Sm)/He analyses of the basal late Eocene turbidites show reset ages of ca. 25 and 20 Ma, respectively, which require temperatures to be >120°C. Homogenization temperatures up to ca. 130°C from fluid inclusion analyses from authigenic minerals confirm the thermochronometric data, supporting a significant post‐depositional heating in the lower sequence of the basin. Stratigraphic reconstructions and decompaction of the basin fill indicate that the maximum burial experienced by the basal strata at 25 Ma is 2.3 ± 0.1 km, which is not sufficient to reset the AFT thermochronometric system when applying a typical geothermal gradient (ca. 20–30°C/km). An elevated geothermal gradient of 45 ± 5°C/km is thus necessary to explain the thermochronometric dates and the elevated thermal signature at shallow depths. 2D numerical simulations indicate that such an elevated palaeo‐geothermal gradient can be best explained by mantle upwelling, consistent with crustal thinning caused by the inception of the Liguro‐Provençal rift basin and related outward migration of the Alpine and Apennine fronts during the Oligocene. [ABSTRACT FROM AUTHOR]

Large numbers of gas reservoirs have been discovered in overpressure basins. Fluid charging has a close relationship with paleo‐pressure evolution, affecting the migration of gas reservoirs. To study fluid charging and the related pressure system, we analyzed burial histories and fluid inclusion (PVTx) simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example. On the basis of fluid‐inclusion assemblages (FIAs), homogenization temperature (Th), final melting temperature (Tm, ice) and Raman spectroscopy in fluid inclusions, there are three stages of fluid charging: during the first and second stage, methane‐dominated fluid was charged at 2.2–1.7 Ma and 1.7–0.9 Ma, respectively. In the third stage, CO2‐rich hydrothermal fluid was charged since 0.9 Ma. It could be concluded from the well‐logging data that the disequilibrium compaction in the Yinggehai Fm., along with the fluid expansion and clay diagenesis in the Huangliu and Meishan formations, resulted in the overpressure in the Ledong slope zone. The evolution of paleo‐pressure was affected by the sedimentation rate of the Yinggehai Fm., as well as the hydrocarbon generation rate. Additionally, the Ledong Slope Zone is less affected by diapir activity than the nearby diapir area. Based on fluid inclusions, paleo‐pressure, basin modeling and geological background, the gas migration history of the Ledong Slope Zone can be divided into four stages: in the first stage, excess pressure was formed around 5 Ma; from 2.2 to 1.7 Ma, there was a reduction in the charging of hydrocarbon fluid and steadily increasing excess pressure; during the 1.7–0.9 Ma period a large amount of hydrocarbon was generated, excess pressure increasing significantly and hydraulic fractures forming in mudstones, With gas reservoirs developing in structural highs; since 0.9 Ma, CO2‐rich hydrothermal fluid accumulated in reservoirs adjacent to faults and the pressure coefficient remained stable. The research results are helpful in the study of fluid migration and accumulation mechanisms in overpressure basins. [ABSTRACT FROM AUTHOR]

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase‐field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high‐temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions. [ABSTRACT FROM AUTHOR]

Lymphangiogenesis is the mechanism by which the lymphatic system develops and expands new vessels facilitating fluid drainage and immune cell trafficking. Models to study lymphangiogenesis are necessary for a better understanding of the underlying mechanisms and to identify or test new therapeutic agents that target lymphangiogenesis. Across the lymphatic literature, multiple models have been developed to study lymphangiogenesis in vitro and in vivo. In vitro, lymphangiogenesis can be modeled with varying complexity, from monolayers to hydrogels to explants, with common metrics for characterizing proliferation, migration, and sprouting of lymphatic endothelial cells (LECs) and vessels. In comparison, in vivo models of lymphangiogenesis often use genetically modified zebrafish and mice, with in situ mouse models in the ear, cornea, hind leg, and tail. In vivo metrics, such as activation of LECs, number of new lymphatic vessels, and sprouting, mirror those most used in vitro, with the addition of lymphatic vessel hyperplasia and drainage. The impacts of lymphangiogenesis vary by context of tissue and pathology. Therapeutic targeting of lymphangiogenesis can have paradoxical effects depending on the pathology including lymphedema, cancer, organ transplant, and inflammation. In this review, we describe and compare lymphangiogenic outcomes and metrics between in vitro and in vivo studies, specifically reviewing only those publications in which both testing formats are used. We find that in vitro studies correlate well with in vivo in wound healing and development, but not in the reproductive tract or the complex tumor microenvironment. Considerations for improving in vitro models are to increase complexity with perfusable microfluidic devices, co‐cultures with tissue‐specific support cells, the inclusion of fluid flow, and pairing in vitro models of differing complexities. We believe that these changes would strengthen the correlation between in vitro and in vivo outcomes, giving more insight into lymphangiogenesis in healthy and pathological states. [ABSTRACT FROM AUTHOR]

Revealing hydrothermal evolution from the early oxide to late carbonate stages for quartz–wolframite vein‐type deposits is essential for understanding the ore‐forming process. In this study, we choose the Baishitouwa tungsten polymetallic deposit located in the southern Great Xing'an Range tungsten belt as a case study, and present detailed deposit geology and in situ fluid inclusion (FI) analyses including microthermometry, laser Raman spectra, and LA‐ICP‐MS microanalysis to address this issue. Four stages of hydrothermal activity were identified: (1) quartz–wolframite (I), (2) quartz–wolframite (II)–pyrite–chalcopyrite, (3) quartz–polymetallic sulphides, and (4) quartz–carbonate. Four types of FIs were recognized: CO2‐rich, CO2‐bearing, liquid‐rich, and brine inclusions. Microthermometric data showed that the homogenization temperatures and salinities from the early to late stages are 380–460°C, 7.4–17.3, and 29.3–43.2 wt% NaCl equiv., 300–390°C and 7.1–17.0 wt% NaCl equiv., 220–320°C and 2.7–8.1 wt% NaCl equiv., and 150–250°C and 0.5–4.8 wt% NaCl equiv., respectively, suggesting a decreasing trend. Geochemically, all stage fluids contained high Rb and Mn concentrations, high Rb/Na, Cs/Na, Li/Na, K/Na, Rb/Sr, low K/Rb, and consistent Cs/Rb and Cs/(Na + K) ratios, indicating that the mineralizing fluids originated from a common source—an underlying, geochemically uniform, and highly fractionated granitic magma. Fluid immiscibility and cooling are the main mechanisms for wolframite precipitation, whereas greisenization is subordinate; the incursion of meteoric water into the hydrothermal system initiated at the sulphide stage, and fluid mixing is the dominant mechanism for sulphide precipitation. [ABSTRACT FROM AUTHOR]

Fluids in sedimentary basins exert a crucial influence on various geological phenomena including natural resource formation. Worldwide drilling projects have revealed that the salinity of sedimentary basinal fluids generally increases with depth, irrespective of lithology, age of sediments, or the presence of a halite bed. However, how these vertical salinity variations are produced and what controls the salinity remain unclear. This work examines a new hypothesis that downward‐increasing salinity variations are a natural outcome of the constant chemogravitational potential condition. In a static environment, the salinity is distributed such that the chemogravitational potential of the solute is constant with depth. Once formed, such a distribution would be maintained because no further migration of the solute would occur. To test the hypothesis, a constant chemogravitational potential distribution model was constructed for NaCl–H2O fluids in the sediment column, and NaCl content at each depth was calculated. The results showed that NaCl content monotonically increases with depth, and the variations are similar to the trend of measured data. However, the data were not necessarily completely reproduced by the model, and deviated in some parts from the calculated profile. Such deviation may indicate fluxing of external fluid occurring in these parts, as the constant chemogravitational potential is vulnerable to an advective flow. Therefore, it is proposed that the constant chemogravitational potential condition is a possible endmember theory, influencing natural salinity variations in a static environment. Key Points: Vertical variations in salinity of sedimentary basinal fluid were simulated under constant chemogravitational potential conditionsThe simulation showed that the salinity increases with depth and the salinity gradient is positively dependent on the geothermThe constant chemogravitational potential distribution is roughly coincident with the data of natural sedimentary basinal fluids [ABSTRACT FROM AUTHOR]

The Tabei Pb–Zn deposit is located adjacent to the well‐known Axi low‐sulphidation epithermal Au deposit in the Tulasu Basin, Chinese Western Tianshan. The homogenization temperatures and salinities of H2O‐rich biphase inclusions in ore‐stage sphalerite and calcite from Tabei range from 100 to 170°C and 0.4 to 6.2 wt% NaCleq, respectively. The δ13CV‐PDB and δ18OV‐SMOW values of calcite range from 0.9‰ to 1.5‰ and 5.6‰ to 6.7‰, respectively. The δ18OH2O and δDH2O values of hydrothermal fluids vary from −7.0‰ to −5.9‰ and −120.8‰ to −111.1‰, respectively. The in‐situ δ34SV‐CDT values of sulphides range from 7.5‰ to 8.0‰ (average 7.7‰). The in‐situ Pb isotopic compositions of galena and (87Sr/86Sr)0 ratios of sphalerite resemble those of Au‐bearing pyrite and quartz of Axi deposit, respectively, as well as the ore‐hosting volcanic rocks. These isotopic compositions indicate that the ore metals were derived from the ore‐hosting volcanic rocks, with the ore‐forming fluids consisting predominantly of circulating meteoric water. The absence of coexisting two‐phase vapour and liquid fluid inclusions and the presence of abundant banded coarse‐grained quartz crystals with dog tooth and comb textures at Tabei, suggest that the sulphides precipitated slowly due to conductive cooling. The high sulphide abundance, sulphide assemblage (pyrite + Fe‐poor sphalerite + galena + chalcopyrite), ore textures and isotopic compositions suggest that Tabei represents an intermediate‐sulphidation epithermal deposit. The Axi‐Tabei Au–Pb–Zn epithermal system constitutes a hybrid consisting of Au veins at shallow level and Pb–Zn veins at depth, suggesting that the base metals remain highly prospective beneath the identified Au orebodies at Axi. [ABSTRACT FROM AUTHOR]

Natural gas, consisting primarily of methane (CH4), has become a major source of clean energy in modern society in many parts of the globe. Recent experimental observations and discoveries of deep‐sourced abiotic CH4 in cold subduction zones indicate the important ability of cold subducted slabs to generate natural gas reservoirs. However, most CH4 flux and reservoirs remain unknown and their potential is overlooked in global carbon flux estimations. Massive abiotic CH4‐rich fluid inclusions (FIs) in garnet and omphacite from ultrahigh‐pressure (UHP) eclogites have been found in the Western Tianshan (WT) UHP metamorphic belt, which provides one ideal case for quantification of abiotic CH4 stored in the cold subducted crust. By two methods, we assess the abiotic CH4 content stored in the Chinese WT HP–UHP metamorphic belt. Our calculations show that at least 113 Mt CH4 is stored in the WT eclogites. We also discuss the implications for CH4 reservoirs in subduction zones worldwide and speculate that the cold subduction zones may represent one of the largest, yet overlooked, sources of abiotic CH4 on Earth, which should not be ignored in the global natural resource and carbon flux estimations. [ABSTRACT FROM AUTHOR]

The Zangalou Cu deposit lies in the Sabzevar volcanic‐plutonic zone, northeastern Iran. The deposit is hosted by the middle Eocene volcanic‐sedimentary sequences and it has been affected by propylitic, carbonate, sericitic, and minor argillic alterations. The volcanics have features typical of calc‐alkaline and metaluminous magmas and are plotted in the continental volcanic arc region. Zircon U–Pb dating of the andesite porphyry yield ages of 41.2 and 38.4 Ma (Bartonian). Ore mineralization occurs as stratabound with open‐space filling, dissemination, veinlet, and replacement textures in mineralized conglomerate, andesite porphyry, and trachyandesite host rocks. Cu content in Zangalou deposit vary from 1,234 g/t to 6.24% which mostly occurred as chalcocite mineral. Fluid inclusion data of mineralization‐related calcites indicate medium salinities (12.8–16.6 wt.% NaCl equivalents) and a wide range of temperatures (154–295°C) and show evidence of fluid cooling trend during the ore formation. The δ13C (between 19.3 and −2.8‰) and δ18OSMOW (between 24.8 and 25.34‰) values of ore‐related calcites suggests a contribution of sedimentary organic matter and marine carbonates as the source of carbon in the ore‐forming fluid. High positive δ34S values (27.8–33.47‰) suggest that the source of sulphur is related to sedimentary country rocks. Mineralization is lithologically and structurally controlled and it is epigenetic. According to geological, petrological, alteration, mineralization textures and geometry of deposit, fluid inclusion, and isotopic studies, the Zangalou deposit is similar to manto‐type deposits. [ABSTRACT FROM AUTHOR]

Lateral sampling of each blasting interval (~ 2.6 m) along a 79 m strike length was conducted for the Hosen 8‐2 vein on the −5 ML (mining level, meters relative to sea level) of the Main ore zone in the Hishikari epithermal Au deposit, Kagoshima, Japan. The horizontal variation of mineral textures, bulk chemical compositions, and fluid inclusion temperatures and apparent salinity of ore fluids were determined. The major gangue minerals of the quartz veins studied include quartz and adularia with minor amounts of calcite and smectite. The major ore minerals include electrum, galena, and sphalerite with minor pyrite, petzite, and hessite. Electrum commonly occurs in a discrete band with microcrystalline quartz, granular adularia, and smectite. The electrum‐bearing band is followed by tabular adularia, and finally by granular or comb quartz. Mineral textures that indicate high degrees of supersaturation with respect to amorphous silica (presently quartz with microcrystalline/mosaic and feathery textures) and adularia (with tabular, rhombic, and granular textures) were common throughout the vein strike. Bulk chemical analyses indicate that Au grade is positively correlated with Ag, Bi, Pb, and Te contents. A bonanza zone with Au grades up to 10,800 ppm occurs in the central part of the Hosen 8‐2 vein on the −5 ML, and is associated with high adularia content, calculated as adularia / (quartz + adularia). The wide lateral variation in the geochemical composition contrasts with the consistent association of electrum with microcrystalline quartz, granular adularia, and smectite throughout the Hosen 8‐2 vein on the −5 ML. Fluid inclusion microthermometry of primary and pseudosecondary inclusions in quartz and adularia yielded histogram modes of homogenization temperature between 160 and 240°C; the most frequent mode is 200–210°C, with most data within ±10°C from this value. The maximum ice‐melting temperature of most samples excluding late comb quartz is −1.5°C, which is equivalent to an apparent salinity of 2.6 wt% NaCl eq. The wide variation in ice‐melting temperatures and apparent salinities (up to 5.2 wt% NaCl eq.) may be due to dissolved CO2 in the fluids, while the sharp decrease in apparent salinity with temperature decrease indicates CO2 loss due to fluid boiling during vein formation. The intimate association of electrum with microcrystalline quartz that recrystallized from amorphous silica indicate sharp boiling and vapor loss as the primary mechanism of Au deposition in the Hosen 8‐2 vein. [ABSTRACT FROM AUTHOR]

Large phenocrysts, known as megacrysts, are focal points for research due to their ability to encapsulate large inclusions suitable for precise chemical analyses. Ankaramite, a distinctive type of undifferentiated volcanic rock, stands out due to its high MgO and CaO contents and the presence of abundant Ca‐rich clinopyroxene (diopside) and less common Mg‐rich olivine phenocrysts. In this study, granitic melt inclusions together with carbonic fluid inclusions were identified within diopside megacrysts of ankaramitic basalt dikes in the Kamisano region, Yamanashi Prefecture, Japan. The identified melt inclusions are completely crystallized and primarily composed of quartz, alkali feldspar, and plagioclase, with smaller amounts of pargasite, augite, apatite, and sulfides. Small amounts of residual glass were also occasionally observed in the inclusions. The average chemical composition of these granitic melts within the inclusions corresponds to that of calc‐alkaline granodiorite and the melts are characterized by low water content (0.38 wt%) and high concentrations of sulfur (7000 ppm), copper, and iron. The findings suggested that the composition of granitic melt inclusions may provide insights into the characteristics of near‐surface hydrothermal metal ore deposits. The diopside megacrysts also contain CO2H2O fluid inclusions, which are completely crystallized and mainly comprised of calcite and chlorite, along with small amounts of quartz. The crystals are interpreted to have formed by the reaction of original CO2H2O fluids and host diopside. The diopside megacrysts are estimated to have started crystallization from tholeiitic basalt at a depth of ~30 km in the lower crust, and trapped fluids and granitic melts as inclusions at a shallower depth when the tholeiitic magma ascended. [ABSTRACT FROM AUTHOR]

The Japón, Tailandia and China Sur deposits in the Pelusa mineralized area correspond to a hematite‐dominant IOCG clan within the coastal Cordillera in the Antofagasta Region, Northern Chile, and their mineralization occurs in basaltic to andesitic volcanic rocks of the Jurassic La Negra Formation. In addition to geological and mineralogical descriptions, bulk chemistry of the host rocks, microthermometric and sulfur isotropic analyses were performed to elucidate ore‐forming characteristics of the three orebodies. Chemical data of the host rocks indicate a subalkaline calc‐alkaline affinity with enrichment of the incompatible LILEs, displaying a typical pattern of igneous rocks formed in subduction zones as a general characteristic of the Jurassic‐Lower Cretaceous magmatic arc. Chalcopyrite is the predominant hypogene copper mineral, that variously occurs as veinlets, disseminations and breccia matrix. Fluid inclusions data indicate formation temperatures of the hypogene mineralization ranging mostly from 186 to 377°C, with a high‐salinity range of 30.1 and 45.0 wt% NaCl. The sulfur isotopic ratios (δ34SCDT) of pyrite and chalcopyrite present a narrow range of values from −10.6 to −7.5‰. The negative values in the limited range imply that sulfide minerals of the Pelusa area were formed under a relatively oxidizing and/or neutral pH condition, compared with other Chilean IOCG deposits. [ABSTRACT FROM AUTHOR]

The Humpa Leu East (HLE) prospect is one of the newly discovered porphyry Cu‐Au prospects in the Hu'u district, Sumbawa Island, Indonesia. The HLE prospect was formed by calc‐alkaline magmatic activity in an active continental margin setting. The prospect is typical calc‐alkaline porphyry Cu‐Au mineralization related to multiphase diorite and quartz diorite porphyry intrusions, which are hosted by andesitic crystalline tuff, volcanic breccia, and andesite lava. Hydrothermal alteration recognized at the surface includes potassic, propylitic, advanced argillic, intermediate argillic, and argillic alteration. Two styles of Cu‐Au mineralization were identified in the HLE prospect, that is, quartz‐sulfide veins and sulfide dissemination, formed in the early, intermediate, and late stages. The early stage is associated with M (magnetite ± bornite ± chalcopyrite), A (quartz + magnetite), and AB (quartz + magnetite + chalcopyrite ± pyrite) veins. These veins were mainly formed in the potassic alteration zone. The intermediate stage is characterized by B (quartz + chalcopyrite + pyrite) and C (chalcopyrite ± pyrite) veins and mainly associated with the chlorite‐sericite and sericite alteration zones. The late stage is mainly associated with D (calcite + gypsum + quartz + pyrite ± chalcopyrite ± sphalerite ± galena) veins with sericite‐chlorite alteration halo. Petrography and electron microprobe analyses indicate that calcite mainly replaced Ca‐rich plagioclase. Fluid inclusion petrography and Raman spectroscopy revealed that monophase vapor inclusions, as well as two‐phase (V + L) and multiphase (V + S + L) fluid inclusions contain CO2 gas. The potassic alteration with significant amounts of calcite is indicative of CO2‐rich fluids, which is uncommon in other porphyry Cu‐Au deposits. On the basis of textural and fluid inclusion analyses, calcite formed by a reaction between Ca‐rich plagioclase and CO2‐rich hydrothermal fluids. The CO2 in the hydrothermal fluids of the HLE prospect was likely derived from the magma. [ABSTRACT FROM AUTHOR]

Stalagmite oxygen isotopes (δ18O) have been used to reconstruct terrestrial paleoclimates during the late Pleistocene and Holocene. However, the interpretation of the δ18O is not straightforward when determining the factor controlling δ18O; temperature or water δ18O. In addition, the water δ18O changes with rainfall intensity (amount effect), rainfall seasonality, and some other factors. Here, we first review the hydrochemical processes and behaviors of the oxygen isotopes and the other proxies in a cave system, which are fundamental for interpretating the paleoclimatic signals. We then introduce the oxygen isotope records of Japanese caves. Some of the Japanese stalagmites demonstrated a δ18O profile that represented a similar pattern to the Chinese stalagmite records, but had relatively small δ18O amplitudes, which can be explained mainly by temperature changes rather than the amount effect. This demands a reversal of the relationship between climate and rainwater δ18O across the Japanese Islands. Using δ18O data for rainwater samples from four sites in Japan (in Niigata, Fukuoka, Gifu and Mie Prefectures), we presents the results of model calculations to verify how the rainfall intensity and the seasonality relate with the δ18O of rainwater. A significant correlation coefficient was observed in Niigata, where the rainfall δ18O decreases with an increase in the annual amount of rainfall, and with a decrease in the winter rainfall. Similar trends were observed in Fukuoka, whereas while the results of Gifu and Mie exhibited no significant trends. Temperature change was would be the main factor controlling the stalagmite δ18O at the latter two sites. For a better understanding of the stalagmite δ18O records, the measurement of fluid inclusions and carbonate clumped isotopes can be used to evaluate the effect of temperature on the stalagmite δ18O, as well as to reconstruct the water δ18O. We predict that the 17O excess in stalagmites reconstructs the seasonal shift in the vapor sources. [ABSTRACT FROM AUTHOR]

Primary multiphase fluid inclusions (MFI) were studied in one eclogite and two granulites from the Cabo Ortegal Complex (COC, NW Spain) by means of Raman imaging, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM‐EDS) and Focused Ion Beam ‐ Scanning Electron Microscopy (FIB)‐SEM. Complementary, secondary MFI in pyroxenites from COC were also investigated. MFI hosted in eclogite and granulites occur along growth zones or in 3D clusters in garnet porphyroblasts suggesting a primary origin at high‐pressure (HP) metamorphic conditions. The mineral assemblage of MFI is mainly composed of Fe‐Mg‐Ca‐carbonates and phyllosilicates ± graphite ± quartz ± corundum ± pyrite ± apatite ± rutile and a fluid phase composed of nitrogen ± methane ± carbon‐dioxide. The mineral proportions vary among the lithologies. Dominant carbonates and hydrous silicates are interpreted as step‐daughter minerals (crystals formed in the MFI after entrapment as a result of fluid–host interaction), whereas apatite, quartz and rutile are considered in part as accidentally trapped minerals since they also occur as crystal inclusions together with MFI in each rock type. Quartz and corundum occur together in MFI in ultramafic granulite and are regarded as step‐daughter minerals in this lithology. These observations suggest that the MFI are products of post‐entrapment reactions of a homogeneous COHN fluid system with the host mineral. Thermodynamic calculations in the CaFMAS‐COHN system confirmed that bulk composition of the MFI in eclogite is similar to the host garnet+COHN composition except for a potential lost of H2O. Carbonation and hydration reaction between the host (i.e. garnet or pyroxene) and the fluid inclusion results in the consumption of all CO2 and part of the H2O from the fluid phase producing Ca‐Fe‐Mg‐carbonates and hydrous step‐daughter minerals, mostly pyrophyllite and chlorite. Nitrogen content of the originally trapped COHN fluid in eclogite was estimated to have a maximum value of 10 mol% at peak HP conditions and 30–40 mol% at retrograde conditions that is within the range of the observed MFI in the residual fluid (13–68 mol%). Pseudosection modelling confirmed the stability of the phase assemblage in the MFI in a specific low‐pressure, low‐temperature stability field (between 300°C and 400°C at pressures < 1 GPa), caused by H2O‐ and CO2‐consuming reactions possibly in a single step. Our findings indicate that such processes in the exhuming HP units may play a role in global nitrogen and carbon cycling as well as potentially contributing to nitrogen and methane supply to subsurface–surface environments during devolatilization in the forearc regions of convergent plate margins. [ABSTRACT FROM AUTHOR]

In Gale crater on Mars, the rover Curiosity has discovered evidence of fluid mobilization of the redox‐sensitive element manganese. We present results for Mn from Curiosity's Alpha Particle X‐ray Spectrometer (APXS), which show that the average MnO concentration in mudstone‐dominated sedimentary units (0.22 wt%) is about one‐half of the concentration in the average Mars crust (0.44 wt%). Geochemical trends indicate that Mn in the sedimentary bedrock, most of which has a basaltic provenance, was leached by chemical alteration and dissolution. In >350 vertical meters of mudstone‐dominated strata, the apparent leaching of Mn and retention of Fe in Fe‐O‐H phase(s) resulted in the fractionation of Fe and Mn, indicating relatively moderate Eh‐pH fluid conditions that were not highly alkaline, reducing, or oxidizing. Exceptions are fracture‐associated, silica‐rich haloes where both Mn and Fe were leached by low pH fluids. The rover also discovered Mn‐rich veins, nodules, and patchy, dark coatings on rock surfaces, which are variably associated with enrichments in Fe, P, Cl, and/or Zn. These Mn‐rich features represent ∼1% of the 1029 APXS measurements acquired over ∼25 km of rover traverse. A thermochemical model shows that dissolved Mn2+ could have been concentrated via evaporation, sublimation, and/or freezing. Manganese was then likely precipitated in localized features when >99.99% of the Mn2+‐bearing water was removed from the system. These findings indicate that Mn was mobile in Gale crater and therefore bioavailable as a potential energy source for life. Plain Language Summary: In Gale crater on Mars, the rover Curiosity has discovered evidence of the mobility of the redox‐sensitive element manganese. We present results for manganese analyses from Curiosity's Alpha Particle X‐ray Spectrometer, an instrument that measures the elemental compositions of martian materials. In most of the layered sedimentary bedrock, manganese concentrations are about one‐half of the average Mars crustal composition (approximated as basaltic soil). Our interpretation of the manganese‐depleted bedrock is that the element was leached by chemical processes involving water. In most of the bedrock, manganese was likely removed in fluids, whereas iron was not, indicating that this occurred under relatively moderate aqueous conditions. The rover has also discovered manganese‐rich veins, nodules, and dark coatings on rock surfaces. These manganese‐rich features are associated with enrichments in iron, phosphorus, chlorine, and/or zinc. We provide a thermochemical model to support the hypothesis that the reduced form of manganese (Mn2+) could have been dissolved in water and concentrated as the water evaporated. Manganese was then deposited in localized features when >99.99% of the Mn2+‐bearing water was removed by evaporation. These findings indicate that manganese was dissolved in Gale crater water and was accessible as a potential chemical energy source for life. Key Points: In Gale crater on Mars, manganese is depleted in bedrock and enriched in nodules, veins, and coatingsManganese was likely leached by aqueous chemical alteration and concentrated in solution via evaporative brine evolution and diagenesisManganese and iron fractionation in mudstone counterindicates highly alkaline, reducing, and/or oxidizing fluid conditions [ABSTRACT FROM AUTHOR]

Proterozoic stratiform VMS‐type Ambaji–Deri Zn–Pb–Cu deposits in the Aravalli‐Delhi mobile belt of North‐West India are hosted within meta‐sedimentary sequences of the South Delhi Terrane. Several fracture‐filled discordant late‐stage base metal mineralised quartz veins have intruded along with the fractures and foliation at very high Pf (σ2 < Pf < σ1) with typical hydrothermal alteration zones. Temperatures estimated from hydrothermal chlorite vary from 226 to 293°C (mean. 260°C). 40Ar‐39Ar dating of hydrothermal muscovite yielded a plateau age of 625.5 ± 3.3 Ma. Detailed fluid inclusion (FI) analysis reveals three types of primary and four types of secondary FI. Primary H2O‐NaCl‐CO2 ± N2 type 1a FI has medium to high salinity (11.21–21.96 wt% NaCl equivalent) and high density (0.90–1.04 g/cm3), while the secondary type 1b FI with same compositions are characterized by medium salinity (~12.6 wt% NaCl equivalent) and lower density (0.89–0.90 g/cm3). Phase separation/fluid immiscibility is the primary mechanism of mineralisation in the Ambaji–Deri that caused the original fluid to evolve separately as gaseous (CO2) type 2a, b and aqueous type 3a, b (H2O‐NaCl) with similar salinity and density for the aqueous inclusions and low density for the gaseous inclusions (lowering up to 0.58 g/cm3). The ore‐forming fluid with magmatic signatures possibly originated from the cooling G3 granites, remobilized the pre‐existing metals, and precipitated at ~265°C and ~1 kbar at the epizonal depths in the dilated fractures. Later these fluids are mixed with meteoric water and evolved into low saline aqueous fluids that produced supergene alterations. [ABSTRACT FROM AUTHOR]

The Choghart iron oxide–apatite (IOA) deposit is one of the largest iron mines of the Bafq district in Central Iran. This deposit is hosted by the Early Cambrian rhyolites, and diabase dikes crosscut both host rocks and the ore bodies. The Choghart rhyolites erupted in a continental arc setting, while the Choghart diabase dikes formed in a back‐arc basin environment. Thorite, minor titanite, and REE‐oxide are the main hosts of Th and REEs. The mineralogy and geochemistry support that the Th–REE mineralization formed at relatively reduced conditions. The presence of calcite accompanied by thorite and titanite suggests that Th and REE probably migrated as carbonate complexes in the mineralizing hydrothermal fluids. Microthermometric data of calcite associated with thorite indicate that the salinity of the ore‐forming fluids varies from 20 to 30 wt% NaCl equivalent with temperature estimates between 300 and 370°C. The narrow range of homogenization temperature and low salinities of the fluid inclusions imply the presence of only one fluid phase in the Th–REE mineralization. The calcite δ13CPDB (−3.9 to −4.1‰) and δ18OSMOW (6.6–7.0‰) support a magmatic source for the ore‐forming fluids. Actinolite δD (5.55–6.72‰) and δ18O (−100.8 to −82.4‰) also suggest a magmatic source of the ore‐forming fluids. Microthermometric data imply that fluid–rock interaction and cooling were critical factors triggering the thorite precipitation at Choghart IOA deposit. Stable isotopic data indicate that post‐magmatic fluids derived from rhyolitic magmas played a significant role in the Th–REE mineralization. [ABSTRACT FROM AUTHOR]

The Xiangshan uranium (U) ore field in South‐east China has been recognized as the largest volcanic‐related hydrothermal U deposit in China since its discovery in the 1950s. The U mineralization at Xiangshan is mostly hosted in felsic volcanic and sub‐volcanic rocks and occurs mainly in veins, which are controlled by high‐angle normal faults in association with haematite, quartz, fluorite, apatite, and pyrite. Likewise, diverse hydrothermal alterations such as haematitization, silicification, fluoritization, and illitization have been identified adjacent to the ore‐bearing faults and outward for tens to hundreds of metres into the volcanic rocks. Situated to the west in the Xiangshan ore field, the Shazhou deposit is the second‐largest U deposit in the Xiangshan volcanic basin. Based on geological field evidence and petrographic observations, the ore‐forming fluids in the Shazhou U deposit can be classified and separated into three stages (early, main, and late): (a) fluids associated with the early mineralization stage are characterized by the oxidizing feature with U‐O hydroxide complexes as the dominant species; (b) fluids from the main mineralization stage were reducing fluids with black–purple fluorite and sulphide complexes of U‐Ti‐O; and (c) fluids from the late‐stage were weakly oxidizing fluids with light purple fluorite and light red calcite complexes of U‐O as the dominant species in the fluid. Fluid inclusions in alteration minerals from the main and late mineralization stage recorded homogenization temperatures (Th) of 280–340°C and 200–260°C, with salinities of 5–17 and 6–10% NaCleqv, respectively. Ore‐forming fluids contain variable amounts of CO2, O2, and H2, in which the volatile content in the main mineralization stage is higher than that in the late stage. The temperature and salinity of the ore‐forming fluids were fluctuating and gradually decreased as the geologic history of the deposit progressed. The δDW‐SMOW values calculated for the ore‐forming fluids range from −97.4 to −65.1‰. The δ18O values of syn‐ore quartz occur mainly between 5.9 and 15.7‰; calculated δ18OW‐SMOW values are between −1.5 and +8.3‰. The δ34SCDT values of syn‐ore pyrite and galena range from 9.7 to 19.7‰. The ore‐forming fluids in the Shazhou U deposit are derived from different sources with a complex geological evolution history. The ore‐forming fluids from the early mineralization stage with high O2 contents may have been primarily derived from post‐volcanic hydrothermal activity. Subsequently, fluids from the main mineralization stage (with lower O2 and high H2 contents) might have originated from the deep‐sourced fluids, where sulphur was carried from the metamorphic basement. Finally, ore‐forming fluids from the late mineralization stage could have been produced by mixing meteoric hydrothermal fluids. Large‐scale fluid immiscibility and boiling occurred during the main mineralization stage, followed by fluid mixing during the late mineralization stage. Boiling and mixing of fluids were the two dominant mechanisms for the deposition of U in the Shazhou deposit. [ABSTRACT FROM AUTHOR]

The Aobaotu Pb–Zn deposit (470,700 t; 1.51% Pb, 2.30% Zn) in the southern Great Xing'an Range, northeastern China, is hosted by the Late Jurassic volcanic tuff and structurally controlled by a near‐east–west‐trending fault. Three stages of mineralization were identified, namely, stage I of quartz ± pyrite veins, stage II of quartz–polymetallic sulphide veins, and stage III of late quartz–calcite veins. The quartz and calcite that formed in the three stages were selected for fluid inclusion and C–H–O isotope analyses. The results show that the ore‐forming fluid of the deposit belongs to the H2O–CO2–NaCl system at a medium temperature (concentrated at 220–300°C) and in low salinity (0.7–12.1 wt% NaCl equiv). The δ13C values of the calcite and ankerite are in the range of −8.4 to −4.8‰, indicating that as a source of deep magma. The δDV‐SMOW and δ18OH2O values of quartz range from −108 to −88‰ and 4.55 to 5.85‰, respectively, indicating that the initial fluid of the Aobaotu deposit was a mixture of residual magmatic and meteoric water. Sulphur isotope analysis of the sulphide minerals, that is, sphalerite, galena, pyrite, and chalcopyrite, yield δ34S value in a range of 1.44–4.94‰, indicating that sulphur is mainly derived from magma. In addition, the Pb isotopic composition of the sulphides indicates that the ore‐forming material has a mixed crust–mantle source. Zircon U–Pb dating suggests that the formation of the Aobaotu deposit is genetically related to the granodiorite porphyry (130.3 ± 0.9 Ma). The combined geochronology and isotopic evidence suggest that the Aobaotu deposit is a magmatic‐hydrothermal vein‐type Pb–Zn deposit, opposite to a volcanic Pb–Zn deposit as suggested before. The Aobaotu deposit formed in an extensional tectonic setting caused by the rollback of the Palaeo‐Pacific Plate. [ABSTRACT FROM AUTHOR]

The Huayuan Pb‐Zn ore district in China, located in western Hunan Province, is a giant carbonate‐hosted Pb‐Zn ore district. The source of ore‐forming brines in this ore district remains poorly constrained. Whether the highly saline brines are derived from evaporated seawater or dissolved evaporates continues to be intensely debated. Carbonate minerals associated with Pb‐Zn mineralization have δ13CV‐PDB and δ18OV‐SMOW values ranging from −5.55‰ to +1.35‰ (mean value of −0.69‰; n = 14) and +16.28‰ to +25.05‰ (mean value of +20.22‰; n = 14), respectively. This indicates that carbonate minerals are dominantly formed from dissolved ore‐hosted carbonate rocks. The δ34S values of sulfides range from +20.2‰ to +36.8‰, with an average value of +30.0‰ (n = 27). These results suggest that sulfur is predominantly derived from the thermochemical sulfate reduction of marine sulfate. The crush‐leach analyzed solute data of fluid inclusions in sphalerite show the ore‐forming fluids have Cl/Br molar ratios range from 118 to 384, and Na/Br molar ratios from 39 to 160 (n = 8). These Cl/Br ratios of hydrothermal fluid are much lower than those of seawater (657 to 564), but are consistent with bittern brines through early halite precipitation. We propose that ore‐forming fluids are mainly derived from evaporitic basin brines, which leached base metals from the basement and/or country rocks. The brine then migrated to the basin margins through clastic rocks of basement and then precipitated sulfides by thermochemical sulfate reduction. [ABSTRACT FROM AUTHOR]

Fibrous calcite bed‐parallel veins (BPVs) are a typical feature of the Upper Jurassic – Lower Cretaceous Vaca Muerta Formation in the subsurface of the Neuquén Basin (Argentina). The formation is considered to be the main source rock in the basin as well as an important unconventional play. This study examines the growth of BPVs through an analysis of core from three wells located along a transect extending for some 150 km from the NE Platform near the basin margin in the east to the Agrio fold‐and‐thrust belt at the Andean deformation front in the west. The main objective is to integrate fluid inclusion data with the palaeothermal and palaeopresure evolution obtained from a regional‐scale 2D basin and petroleum systems model to examine the timing of fracture development and its relationship with hydrocarbon generation in the Vaca Muerta Formation through time. The apertures of BPVs were measured in more than 360 m of core from three wells (wells A, D and E). This data was combined with optical petrography to investigate the number of calcite cementation events, and the temperature of cement precipitation based on fluid inclusion data. The organic geochemical and mineralogical characteristics of the Vaca Muerta source rock were also analysed. The integrated results were incorporated into a poro‐elastic basin model to investigate the impact of horizontal shortening due to Andean compression on pore pressure development and fracturing in the Vaca Muerta Formation. This framework allowed the timing of BPV formation to be determined together with possible mechanisms governing overpressure conditions through time. Near the Andean deformation front in the west of the modelled section where the Vaca Muerta Formation is in the wet gas window (well D) and dry gas window (well A), BPVs are characterized by two or more generations of calcite fibres indicating multiple growth phases. Calcite which precipitated during cementation event 1 (E1) in the internal zones of BPVs consists of crystals oriented perpendicular to fracture walls, indicating perpendicular vein opening. Calcite precipitated during cementation event 2 (E2) in the outer zones of BPVs includes curved and oblique crystals. During this phase, shear occurred between the opening vein walls as a result of horizontal shortening. Cementation event 3 (E3) is characterized by an equant mosaic of calcite crystals which preserve intracrystalline porosity. E1cements formed between 110 and 90 Ma with trapping temperatures of ∼112 °C (upper Vaca Muerta, well A) and ∼125 °C (lower Vaca Muerta, well D). Fracturing resulted from disequilibrium compaction and from volumetric expansion due to primary cracking of kerogen within the oil window. E2 cements record a trapping temperature of ∼159 °C and formed between 70 and 55 Ma (lower Vaca Muerta, well D) during maximum burial of the Vaca Muerta Formation, synchronous with the secondary cracking of retained liquid hydrocarbons and the beginning of Andean compression. E3 cements (upper Vaca Muerta, well A) have a trapping temperature of ∼162 °C, and formed between 65 Ma and 53 Ma synchronous with the generation of thermogenic gas. By contrast, in the east of the modelled section in the less deformed foreland area of the Neuquén Basin where the Vaca Muerta Formation is in the early oil window (well E), BPVs are composed of a single generation of calcite fibres (E1)with a trapping temperature of ∼118 °C. The E1 cement is characterized by calcite crystals which are oriented perpendicular to fracture walls with no evidence of shearing. According to model simulations, cementation here occurred between 64 Ma and 53 Ma during maximum burial and was related to overpressures which resulted from both disequilibrium compaction and primary transformation of kerogen into oil. The data presented suggests that in some intervals of the Vaca Muerta Formation, a slight increase in TOC content is accompanied by an increase in vein thickness, with the highest number of cementation events occurring towards the Andean deformation front in the west of the study area compared to the foreland in the east. [ABSTRACT FROM AUTHOR]

This work evaluates an exceptionally complex natural laboratory, the Middle Triassic Latemar isolated platform in the northern Italian Dolomite Mountains and explores spatial and temporal gradients in processes and products related to contact metamorphism, dolomitization and dedolomitization of marine limestones. The relation between petrographic change and re‐equilibration of geochemical proxy data is evaluated from the perspective of carbonate‐archive research. Hydrothermal dolomitization of the limestone units is triggered by dykes and associated hydrothermal fluids radiating from the nearby Predazzo Intrusion. Detailed petrography, fluid inclusion analysis, δ13C and δ18O data and 87Sr/86Sr isotope ratios shed light on the extreme textural and geochemical complexity. Metamorphic and diagenetic patterns include: (i) peak‐metamorphic and retrograde‐metamorphic phases including three dolomite marbles, two dedolomite marbles, brucite, magnesium silicates and late‐stage meteoric/vadose cement at the contact aureole; (ii) four spatially defined episodes of dolomitization, authigenic quartz, low magnesium calcite and late‐stage meteoric cement at the Latemar isolated platform; and (iii) kilometre‐scale gradients in δ13C values from the contact aureole towards the platform interior. Results shown here are relevant for two reasons: first, the spatial analysis of alteration products ranging from high‐grade metamorphic overprint of marbles at temperatures of 700°C in the contact aureole to moderately altered limestones in the platform interior at temperatures <100°C, allows the observation of processes that commonly occur along vertical (prograde) gradients from shallow burial to metamorphism at depths >20 km. Second, under rock‐buffered conditions, and irrespective of metamorphic to diagenetic fluid−rock interactions, both marbles, and low‐temperature hydrothermal dolomites have conservative marine δ13C and δ18O values. The fact that metamorphism and hydrothermal dolomitization of precursor limestones and early diagenetic dolostones did not per se reset environmental proxy data is of interest for those concerned with carbonate archive research in Earth's deep time. [ABSTRACT FROM AUTHOR]

Detachment faults are sites of intensive fluid–rock interactions. Here, we report fluid inclusion and oxygen isotope data for quartz veins in the Ramba Dome in the North Himalayan Gneiss Domes, with an aim to constrain the origin and circulation of crustal fluids associated with the South Tibetan Detachment System (STDS). Microthermometric data for fluid inclusions in quartz indicate that the fluids were aqueous and CO2 − H2O ± CH4 ± N2‐bearing with low to moderate salinities (0.60–11.80 wt% eq. NaCl). The entrapment conditions are 295–410°C and 98–135 Mpa, indicating a forming‐depth of 8–10 km. Oxygen isotopic compositions (δ18O) of quartz measured in situ by secondary ion mass spectrometry and bulk by the BrF5 method show limited variations in individual quartz veins, but δ18Oquartz values vary from 12.07 to 18.16‰ (V‐SMOW) among veins. The corresponding δ18Ofluid values range from 7.71 to 13.80‰, based on equilibrium temperatures obtained from fluid inclusions. From the footwall to the detachment zone, δ18Ofluid values exhibit a broadly decreasing trend and indicate that the STDS dominated the fluid flux pathway in the crust, with more contributions of meteoric water in the detachment zone. We further quantified the contribution of meteoric fluids to 8–27% using a binary end‐member mixing model. These data imply that the fluids were predominantly metamorphic/magmatic in origin, and were mixed with infiltrating, isotopically light, meteoric water during extensional detachment shearing of the STDS. The meteoric water can infiltrate from the surface to 8–10 km depth. [ABSTRACT FROM AUTHOR]

The southern Jiangxi Province is an important part of the fluorite mineralization belt in South China. Fluorite ore bodies are primarily in the contact zone between the Devonian Huitong granitic complex and the Late Cretaceous Ganzhou Formation, controlled by the NE‐trending faults. Zircon U–Pb dating of the Huitong granitic complex yields emplacement ages of 410.7 ± 1.4 Ma and 400.7 ± 4.6 Ma, while the Sm–Nd dating of the fluorite yields an isochron age of 94 ± 2 Ma, suggesting that the Huitong granitic complex is the host rock. Fluid inclusions in the fluorite show low homogenization temperatures (136–207°C), salinities (1.23–3.87 wt% NaCl), and densities (0.87–0.95 g/cm3), suggesting that the ore‐forming fluid is an NaCl‐H2O system of low temperature, salinity, and density. Raman spectroscopy showed that the fluid phase is dominated by water. The δDVSMOW values of the fluid inclusions in the Tongda fluorite ranged between −59.5 and −55.2‰, while the δ18OVSMOW values of the fluorite ranged from −7.2 to −5.6‰. Collectively, the ore‐forming fluid is dominated by meteoric water, possibly with a minor contribution of hydrothermal fluid. Both the interaction with host rocks and the cooling of hydrothermal fluids are the likely mechanisms of underlaying fluorite precipitation at low temperatures. The mineralization occurred in extensional faults during the Late Cretaceous related to the subduction of the Palaeo‐Pacific Oceanic Plate. [ABSTRACT FROM AUTHOR]

Interpretation of various exploration data, in particular geochemical prospecting, offers a powerful and rapid assessment of grass‐root projects in a green‐field terrain. Here, we present an example of the Collins epithermal prospect in Aceh Province, Indonesia. In this area, the Au+ base‐metal‐bearing sheeted quartz veins (individually mostly 2–4 cm wide), which are controlled by a 250 m wide by 800 m long NNE‐trending structural corridor within Paleogene sandstone and volcanic rocks, are the product of two main stages of deposition. Stage I formed veins with a sliver of cryptocrystalline quartz wall zone followed by an inner zone of comb quartz with interstitial rhombic adularia that terminates in open space. Stage I or main‐stage sulfide mineralization consisting of early galena + sphalerite and later chalcopyrite occurs with the quartz + adularia. Small amounts of galena also occur in the wall zone. Stage II mineralization brecciated Stage I veins and overprinted them with silicification characterized by vuggy texture. Mineralization associated with this episode consists of earlier chalcopyrite + sphalerite + tennantite–tetrahedrite and later, vug‐filling Au–Ag alloy (Ag0.37–0.41Au0.62–0.59). The above mineralized veins are successively flanked by silicic selvages, an illite + chlorite + pyrite ± kaolinite zone and a chlorite + epidote + carbonate + pyrite zone. Local supergene alteration induced replacement of galena by plumbogummite and anglesite and chalcopyrite by covellite. Data from fluid inclusion microthermometry in quartz indicated that the inner zone of Stage I veins formed from fluids with a 2.3 wt% salinity (0.5–3.3 wt% NaCl equivalent), at 174°C (155–211°C). Combining these physico‐chemical parameters with the mineral assemblage, the mineralization occurred under a reduced environment. Rock and soil assays indicate that elevated Au concentrations (up to 16.5 ppm over 1 m) occur along northeast‐trending zones and show a strong correlation with Pb, while Cu (up to 2.58% over 1 m), Zn, As, Sb, and Mo anomalies lie mostly at the periphery. The high‐grade mineralized veins correlate with moderate to high resistivity and chargeability zones, and the pseudosections of such geophysical signals are interpreted as reflecting coalesced or enlarged veins at depth, or inclined veins in other localities. The intermediate sulfidation affinity for Collins points to potential mineralization at depth as well as preservation of Au‐rich and sulfide‐poor zones in the less eroded areas. [ABSTRACT FROM AUTHOR]

In hyperalkaline (pH>10) fluids that have participated in low‐temperature (<150°C) serpentinization reactions, the dominant form of C is often methane (CH4), but the origin of this CH4 is uncertain. To assess CH4 origin in serpentinite aquifers within the Samail Ophiolite, Oman, we determined fluid chemical compositions, analyzed taxonomic profiles of fluid‐hosted microbial communities, and measured isotopic compositions of hydrocarbon gases. We found that 16S rRNA gene sequences affiliated with methanogens were widespread in the aquifer. We measured clumped isotopologue (CH313D and CH212D2) relative abundances less than equilibrium, consistent with substantial microbial CH4 production. Furthermore, we observed an inverse relationship between dissolved inorganic C concentrations and δ13CCH4 across fluids bearing microbiological evidence of methanogenic activity, suggesting that the apparent C isotope effect of microbial methanogenesis is modulated by C availability. An additional source of CH4 is evidenced by the presence of CH4‐bearing fluid inclusions in the Samail Ophiolite and our measurement of high δ13C values of ethane and propane, which are similar to those reported in studies of CH4‐rich inclusions in rocks from the oceanic lithosphere. In addition, we observed 16S rRNA gene sequences affiliated with aerobic methanotrophs and, in lower abundance, anaerobic methanotrophs, indicating that microbial consumption of CH4 in the ophiolite may further enrich CH4 in 13C. We conclude that substantial microbial CH4 is produced under varying degrees of C limitation and mixes with abiotic CH4 released from fluid inclusions. This study lends insight into the functioning of microbial ecosystems supported by water/rock reactions. Plain Language Summary: Mantle rocks from beneath Earth's crust can be thrust to the surface, where they are exposed to rain and air containing carbon dioxide (CO2). The groundwaters that become stored in these rocks often contain methane (CH4, a major component of "natural gas"), which can be formed from carbon dioxide in the subsurface. To investigate these methane‐forming processes, we sampled water, gas, and suspended particles from groundwaters using wells previously drilled into the rocks. The particles contained microbes with the genetic ability to produce methane. We also precisely measured the amounts of combinations of C and H atoms of different masses (isotopes) in the natural gas to determine how it was formed. The results of these measurements suggest that microbes could actively produce a considerable amount of the methane, which mixes with methane from another source that was formed by non‐biological processes, possibly long ago under different conditions than today's. Rocks like those studied here are widespread in the Solar System, so our finding that microbes live and produce methane in these rocks could help guide the search for life beyond Earth. Key Points: 16S rRNA gene sequences affiliated with methanogens and CH4 clumped isotopologue compositions suggest substantial microbial CH4 productionA second CH4 source, release of CH4 from fluid inclusions, is indicated by 13C‐enriched ethane and propaneC availability may influence the apparent C isotope effect of microbial methanogenesis [ABSTRACT FROM AUTHOR]

Despite high pressure being ubiquitous in the Yanan Sag of the Qiongdongnan Basin, South China Sea, its potential effect on gas migration‐accumulation remains unclear. In this study, a series of geochemical indicators combined with the origin of high pressure were used to elucidate the cause of gas accumulation failure in the overpressured YC19‐1 structure. Drill‐stem tests, mud weights, and well‐loggings reveal two vertical overpressure systems. Pore pressure in the deep Lingshui and Yacheng formations almost reaches a lithostatic magnitude, which was interpreted as a result of gas generation and disequilibrium compaction triggered by the Pliocene‐Quaternary rapid subsidence. A thermal anomaly above the high‐pressure system was evidenced by high homogenization temperature (Th) of fluid inclusion, abnormally high vitrinite reflectance, and a rapid transformation from kaolinite to illite. The high thermal field likely resulted from a cross‐stratal fluid migration from the deep high‐pressure system. Both methane‐bearing inclusions in sandstones and abnormal Rock‐Eval data of mudstones above the high‐pressure surface suggest an influx of external hydrocarbons. Based on primary aqueous inclusion Th and salinity, carbon and oxygen isotope compositions, and petrographic observations, widespread silica and carbonate cements near the overpressure surface were interpreted to be derived from extraformational materials carried by deep‐seated basinal fluids. Fluid inclusion Th coupled with burial model suggests that the gas leakage took place at circa 1.6 Ma, coinciding well with the stages of both gas generation and overpressure. These observations suggest an upward leakage of gas‐bearing fluids induced by pressure release, thus leading to the existence of only non‐commercial gas‐bearing aquifers in the overpressured YC19‐1 structure. [ABSTRACT FROM AUTHOR]

The Yuku is a large porphyry Mo deposit (1.5 Mt at 0.12% Mo) in the Luanchuan ore district of the East Qinling orogen, central China. The economic Mo ore bodies occur as veins, veinlets, and disseminated ore and are developed mainly within the late Mesozoic Yuku porphyritic granite. Molybdenum mineralization is generally associated with potassic and phyllic alteration. Hydrothermal processes in the Yuku deposit are divided into four stages: (I) a quartz–K‐feldspar–biotite ± pyrite stage, (II) a quartz–molybdenite ± pyrite ± K‐feldspar ± sericite stage, (III) a quartz–polymetallic sulphide stage, and (IV) a calcite ± quartz ± fluorite ± pyrite stage. The fluid evolution during these hydrothermal stages was constrained through systematic investigation of fluid inclusions (FIs) and H−O isotopes. Four types of primary or pseudosecondary FIs were recognized in hydrothermal quartz and calcite: two‐phase liquid‐rich inclusions (L‐type), two‐phase vapour‐rich inclusions (V‐type), halite‐bearing (hypersaline) inclusions (H‐type), and three‐phase CO2‐bearing inclusions (C‐type). FIs within Stages I–IV have homogenization temperatures of 375 to >550, 297–400, 198–298, and 149–188°C, with salinities of 0.53–13.18, 0.35–40.23, 5.11–11.81, and 5.71–9.73 wt% NaCl equiv., respectively. In Stage I, coexisting vapour‐rich (V‐type) and liquid‐rich (L‐type) FIs have similar homogenization temperatures (488 to >550°C) and distinct salinities, indicating fluid boiling during the formation of quartz–K‐feldspar–biotite veins at a pressure of 550–700 bar and a lithostatic depth of 2.3–2.8 km. In Stage II, FIs in quartz were also trapped under boiling conditions, as evidenced by coexisting hypersaline H‐type (34.13–40.23 wt% NaCl equiv.) and low‐salinity V‐type (0.35–2.24 wt% NaCl equiv.) inclusions, which formed at temperatures of 309–361°C and hydrostatic depths of 1.0–2.0 km, equivalent to pressures of 100–200 bar. During Stage III, the ore‐forming fluids were cooler (198–298°C) and more dilute (5.11–11.81 wt% NaCl equiv.) due to the involvement of meteoric water, with minimum trapping pressures estimated at <100–150 bar, corresponding to a hydrostatic depth of <1.0 km. In Stage IV, temperatures decreased further to 149–188°C, with lower salinities (5.71–9.73 wt% NaCl equiv.), indicating a post‐ore fluid stage. These data suggest that the mineralizing fluids forming the Yuku Mo deposit changed from early moderate‐ to low‐salinity CO2‐rich fluids in the H2O–NaCl–CO2 system that formed at high temperature and pressure, to late H2O–NaCl low‐salinity fluids that formed at low temperature and pressure. H−O isotopic compositions indicate that the mineralizing fluids had a dominantly magmatic signature but were diluted by meteoric waters. Combining our integrated analysis of the fluid evolution and deposit geology, we propose that fluid boiling and fluid–rock interaction, including intensive potassic alteration, changed the salinity and triggered CO2 escape, leading to a decrease in fO2 and an increase in the acidity of the ore‐forming fluids, which ultimately controlled the deposition of molybdenite in the Yuku Mo deposit. [ABSTRACT FROM AUTHOR]

The Chinese Altay in Northwest China and adjacent regions in the Russian and Mongolian Altay form a tungsten province within the Central Asian Orogenic Belt. Unlike the Russian and Mongolian Altay, almost no tungsten deposits in the Chinese Altay have been reported. The Basitielieke deposit located in the Altay orogenic belt in Xinjiang is a newly discovered polymetallic tungsten deposit hosted in the skarn in the exocontact zone of a granite pluton. Mineralization can be divided into the skarn period and supergene oxidization period, the skarn period can be further divided into a prograde skarn stage (I), a retrograde skarn stage (II), and a quartz–sulphide stage (III). Scheelite mineralization mainly occurred in stage II, and Cu–Zn–Au formed in stage III. The ore‐forming fluid can be divided into a H2O–NaCl systems, including stage I (211 to 480°C and 2.24 to 14.04 wt% NaCl equiv) and stage II (178 to 336°C and 4.96 to 9.47 wt% NaCl equiv), and a H2O–CO2 (±CH4/N2)–NaCl system in stage III (130 to 434°C and 1.40 to 9.60 wt% NaCl equiv). Hydrogen, oxygen, and sulphur isotope compositions indicate that magmatic water participated in the hydrothermal mineralization system in stage I, and meteoric water increased with the process of mineralization. Sulphur was derived from deep‐seated magmas. The Basitielieke deposit is a reduced skarn polymetallic tungsten deposit. The deposit formed by hydrothermal fluid from the granite interacting with strata during the Early Permian, the fluid–rock interaction and fluid mixing (magmatic water and meteoric water) was the main precipitation mechanism of the Basitielieke polymetallic tungsten deposit. [ABSTRACT FROM AUTHOR]