Search

Significant progress has recently been made in deep and ultra-deep oil and gas exploration globally, demonstrating enormous exploration potential of the deep and ultra-deep strata. However, the accumulation and preservation pattern of deep and ultra-deep oil and gas remains poorly understood, greatly impeding further petroleum exploration and development in the deep and ultra-deep strata. By taking the Bozi deep and ultra-deep condensate gas reservoirs in the Kuqa Depression, western China as an example, we attempt to reconstruct the hydrocarbon charge history in such deep reservoirs via an integrated investigation involving quantitative grain fluorescence, fluid inclusion petrography and microthermometry, micro-fluorescence spectroscopy, laser Raman spectroscopy, PVTx modelling, and basin modelling. The results show that: (1) The Bozi deep and ultra-deep reservoirs contain one group of gas inclusion assemblage, and two groups of oil inclusion assemblages, with one being characterized by near yellowish-whitish and blue-whitish diphasic or triphasic oil inclusions, and the other being featured by bright blue diphasic oil inclusions; (2) The first oil charge occurred during the Early Neogene (6.5-5.5 Ma), and the second oil charge occurred during the Late Neogene (4.4-3.5 Ma), under normal hydrostatic pressure or slightly weak overpressure; and (3) The gas charge occurred during the Pleistocene (∼1.6 Ma), with a corresponding reservoir pressure coefficient of approximately 1.7, transforming the reservoir fluid phase state from black oil or volatile oil to condensate gas. Our findings highlight that aside from the present burial depth, a favorable burial history model is crucial for the preservation of liquid hydrocarbons in deep and ultra-deep reservoirs. The occurrence of liquid hydrocarbons in the Bozi deep and ultra-deep condensate gas reservoirs with depths over 7,000 m is benefited from a prolonged period (>100 Ma) of shallow burial and a late-stage (since 10 Ma) rapid subsidence. [ABSTRACT FROM AUTHOR]

Carbon with depleted d13C (down to − 25.6‰ VPDB) found in > 3.7 billion year old metamorphic sediments from the Isua Supracrustal Belt, Southwestern Greenland, has been proposed to represent the oldest remains of life on Earth. Graphitic inclusions within garnet porphyroblasts from this locality have been shown to associate with elements consistent with biogenic remains. In this report, we focus on certain liquid inclusions found in the Isua garnets, characterizing their chemical composition using atomic force microscopy, AFM-based infrared spectroscopy, optical photothermal infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. Our results show that the liquid inclusions contain functional groups consisting of carbon, nitrogen, and oxygen in a configuration similar to amide functional groups. We suspect that the amide groups formed from N, O and C-containing volatile components that were released from the original kerogenous material enclosed in the garnets, as this was graphitized during thermal maturation. This is consistent with the observed inclusion assemblage of solid graphitic and viscous fluid inclusions alike. Our observations are compatible with the inclusions forming from biogenic precursor material, and when considered alongside previous reports on the carbonaceous material in the Isua metamorphic sediments, these and our study collectively indicate that the carbonaceous material in the Isua metasediments represents the oldest traces of life on Earth. [ABSTRACT FROM AUTHOR]

The Chazangcuo copper-lead-zinc deposit (hereafter referred to as the Chazangcuo deposit) is situated in the northern portion of the western section of the Gangdese polymetallic metallogenic belt in Tibet, with ore bodies strictly governed by Linzizong Group magmatic rocks and EW-trending faults. This study aims to ascertain the mineralization periods, sources of oreforming materials, metallogenic physicochemical conditions, and genesis of this deposit. Based on comprehensive field geological surveys, sampling, and microscopic examination of petrological and mineralogical characteristics, we perform qualitative and quantitative geochemical analyses of major elements, trace elements, and rare earth elements (REEs), fluid inclusions, and sulfur and lead isotopes. The findings reveal that the mineralization process of the Chazangcuo deposit can be divided into three periods and four stages: the magmatic-hydrothermal, hydrothermal, and supergene mineralization periods sequentially, which consist of the mineralization stages of quartz-pyritesphalerite, medium-low-temperature hydrothermal sulfides, chlorite-carbonate minerals, and supergene oxidation in a chronological order. The ore-forming fluids prove to be medium-low-temperature low-density fluids, and the oreforming materials are characteristic of upper crustal-derived materials. The ore-forming environment is a medium-low mineralization temperature, a shallow and weakly reducing environment. Overall, the Chazangcuo deposit is identified as a medium-low-temperature magmatic-hydrothermal deposit. The metallogenic model has the vertical zoning characteristics of lead-zinc in the upper part and copper in the lower part. [ABSTRACT FROM AUTHOR]

The Guanpo pegmatite field in the North Qinling orogenic belt (NQB), China, hosts the most abundant LCT pegmatites. However, their emplacement conditions and structural control remain unexplored. In this contribution, we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study. The orientations of type A1 pegmatites (Pf < σ2) are predominantly influenced by P‐ and T‐fractures due to simple shearing in Shiziping dextral thrust shear zone during D2 deformation, whereas type A2 pegmatites (contemporaneous with D4) are governed by hydraulic fractures aligned with S0 and S0+1 stemming from fluid pressure (Pf <σ2). Additionally, type B pegmatites (Pf ≤ σ2) exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones (contemporaneous with D3). The albite‐quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites (including types B and A2) suggest that the crystallization P‐T for late magmatic and hydrothermal stages are 527.5–559.2°C, 320°C, 3.1–3.6 kbar and 2.0 kbar, respectively. Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long‐term, multi‐stage event during early Paleozoic orogeny (including the collision stage) of the NQB, and was facilitated by various local fractures. [ABSTRACT FROM AUTHOR]

The Batailing Au deposit is a vein-type deposit in central Jilin Province, situated in the southern sector of the Lesser Xing'an–Zhangguangcai Range within the eastern Central Asian Orogenic Belt. NE-trending fault-controlled orebodies occur in the Upper Permian Yangjiagou Formation and quartz diorite–porphyrite. The mineralisation process was delineated into three stages: (I) quartz–arsenopyrite–pyrite, (II) quartz–polymetallic sulphides (main Au mineralisation stage), and (III) quartz–pyrite–carbonate. Fluid inclusions (FIs) in quartz were identified as four types: PC-type (pure CO2), C1-type (CO2-bearing), C2-type (CO2-rich), and W-type (aqueous two-phase). Raman spectroscopy analysis revealed that the vapor components of the FIs predominantly comprised CO2 with minor quantities of CH4 in stages I–II. Stages I and II encompassed four types of FIs with homogenisation temperature ranging from 264 to 332 °C and 213 to 292 °C and salinity spanning from 4.7 to 11.2 wt% and 1.8 to 11.6 wt%, respectively. Stage III exclusively contained W-type FIs with homogenisation temperature ranging from 152 to 215 °C and salinity spanning from 1.4 to 6.4 wt%. H-O isotopic values (δD = −84 to −79.6‰, δ18OH2O = 6.2 to 6.4‰ in stage I and δD = −96.4 to −90.4‰, δ18OH2O = 2.8 to 4.4‰ in stage II) and microthermometric data indicated that the ore-forming fluids are initially from a magmatic source, with later meteoric water input. Low C isotopic data from CO2 in FIs in quartz (−24.4 to −24.3‰ in stage I and −23.7 to −22.6‰ in stage II) indicated an organic carbon source. Ore precipitation is mainly attributable to fluid immiscibility. S-Pb isotopic data (δ34S = −3.5 to −1.6‰; 206Pb/204Pb = 18.325–18.362, 207Pb/204Pb = 15.523–5.562, 208Pb/204Pb = 38.064–38.221) revealed that ore metals primarily originated from magma. Based on this research, the origin of the Batailing Au deposit is of the mesothermal magmatic–hydrothermal lode type. [ABSTRACT FROM AUTHOR]

The Southern Hunan area is located in the superposition of the Qin-Hang Cu-Pb-Zn polymetallic ore belt and the Nanling W-Sn-Mo polymetallic ore belt, which is an important window to study the mineralization of W-Sn-Mo and Cu-Pb-Zn polymetallic deposits. The Baoshan deposit is a large Cu-Pb-Zn polymetallic deposit in Southern Hunan Province with obvious zones of Cu mineralization and Pb-Zn mineralization: the central part of the Baoshan deposit demonstrates contact metasomatic (skarn) Cu mineralization, while the western, northern and eastern parts demonstrate hydrothermal vein Pb-Zn mineralization. However, the origin and evolution of the ore-forming fluid and mechanism of Cu and Pb-Zn mineral precipitation are still unclear. The metallogenic process of the Baoshan Cu-Pb-Zn deposit can be divided into four stages: (1) the early skarn stage (S1); (2) the late skarn stage (S2); (3) the Cu-Fe sulfide stage (S3); and (4) the Pb-Zn sulfide stage (S4). The results of microtemperature measurements and a Raman spectrometric analysis of fluid inclusions show that the ore-forming fluid was the H2O-NaCl (-CO2 ± N2 ± C2H6) system in the skarn stages (S1 + S2) and changed into the H2O-NaCl-CO2 (±N2 ± C2H6) system in the sulfide stages (S3 + S4). The temperature (S1: 436.6~548.2 °C; S2: 344.1~435.1 °C; S3: 134.1~413.1 °C; S4: 183.9~261.0 °C) and salinity (S1: 17.4~51.2 wt.%NaClequiv; S2: 13.6~41.7 wt.%NaClequiv; S3: 1.2~32.3 wt.%NaClequiv; S4: 1.8~9.6 wt.%NaClequiv) showed a downward trend from the early to late stages. From the skarn stages (S1 + S2) to the sulfide stages (S3 + S4), the ore-forming pressure results from the static rock pressure and the hydrostatic pressure, and the ore-forming depth is estimated to be about three to six km. The C-H-O isotopic compositions of hydrothermal minerals such as quartz and calcite indicate that the ore-forming fluid is predominately magmatic fluid, but a significant amount of meteoric water is added in the Pb-Zn sulfide stage (S4). The formation of the mineralization zonation of the Baoshan deposit is the result of many factors (e.g., stratigraphy, structure and metal precipitation mechanism): the Cu mineralization is controlled by the contact zone, and the Pb-Zn mineralization is controlled by the fault. In addition, the precipitation of Cu is mainly controlled by fluid boiling, while the precipitation of Pb and Zn is mainly controlled by the mixing of magmatic fluid and meteoric water. [ABSTRACT FROM AUTHOR]

The Xianghualing large tin-polymetallic skarn deposit is located in the Nanling W-Sn metallogenic belt, South China, showing distinct spatial zoning of mineralization. From the contact between granite and carbonate rocks, the mineralization transitions from proximal skarn Sn ore to cassiterite-sulfide ore and more distal Pb–Zn-sulfide ore. This study reveals the fluid evolution and genetic links among these different ore types. The physical and chemical characteristics of fluid inclusions from each ore types indicate that the skarn Sn ore, cassiterite-sulfide ore, and Pb–Zn-sulfide ore all originated from the identical magmatic fluid exsolved from the Laiziling granite. Their formation, however, is controlled by diverse fluid evolutionary processes and host rock characteristics. The Sn–Pb-Zn-rich fluids were primarily derived from cooled and diluted magmatic brine, which is generated by boiling of initial single phase magmatic fluid. Mixing of magmatic brine with meteoric water is crucial to form skarn Sn ore. Redox reactions of aqueous Sn (II) complexes with As (III) species and/or minor CO2 during short cooling period of ore-forming fluid is likely an effective mechanism to form high-grade cassiterite-sulfide ores, accompanied by favorable pH conditions maintained through interaction with carbonate host rocks. The later stage addition of meteoric water prompts the formation of Pb–Zn-sulfide ore. Comparing these findings with the characteristics of initial or pre-ore magmatic fluids in both mineralized and barren granitic systems indicates that high Sn content in the pre-ore fluids and the suitable fractional crystallization degree of the parent magma may determine high Sn mineralization potential in granitic magmatic-hydrothermal systems. [ABSTRACT FROM AUTHOR]

Abstract Carbon with depleted d13C (down to − 25.6‰ VPDB) found in > 3.7 billion year old metamorphic sediments from the Isua Supracrustal Belt, Southwestern Greenland, has been proposed to represent the oldest remains of life on Earth. Graphitic inclusions within garnet porphyroblasts from this locality have been shown to associate with elements consistent with biogenic remains. In this report, we focus on certain liquid inclusions found in the Isua garnets, characterizing their chemical composition using atomic force microscopy, AFM-based infrared spectroscopy, optical photothermal infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. Our results show that the liquid inclusions contain functional groups consisting of carbon, nitrogen, and oxygen in a configuration similar to amide functional groups. We suspect that the amide groups formed from N, O and C-containing volatile components that were released from the original kerogenous material enclosed in the garnets, as this was graphitized during thermal maturation. This is consistent with the observed inclusion assemblage of solid graphitic and viscous fluid inclusions alike. Our observations are compatible with the inclusions forming from biogenic precursor material, and when considered alongside previous reports on the carbonaceous material in the Isua metamorphic sediments, these and our study collectively indicate that the carbonaceous material in the Isua metasediments represents the oldest traces of life on Earth.

In order to constrain the granitic magma source at the northeastern continental margin of the Eurasian plate, noble gas isotopic ratios such as helium (3He/4He), argon (40Ar/36Ar) and neon (20Ne/22Ne, 21Ne/22Ne) were determined for Mesozoic quartz and biotite minerals from granitic rocks in the Korean peninsula. 3He/4He ratios in fluid inclusions of quartz samples have a wide range from 0.005 to 0.522 RA (av. 0.095 RA) and 0.013 to 1.27 RA (av. 0.37 RA) (RA =1.40 × 10−6, atmospheric value) for Jurassic (Daebo) and Cretaceous (Bulguksa) granites, respectively. The 3He/4He ratios clearly show a contribution of mantle-derived He to the granitic rock at the formation, then the helium has been deeply affected by accumulation of in situ produced radiogenic 4He and/or crustal helium. Although these ratios are lower than those of the subcontinental lithospheric mantle (SCLM) (6.1 ± 0.9 RA), mantle helium has been traced in these Mesozoic I-type granites from South Korea. The observations imply that the helium of SCLM source predominates over all of the Jurassic granites in South Korea and the Cretaceous granites in the Ogcheon belt (OB), and suggests that the granitic magma was derived from the partial melting product of SCLM materials with appreciable amounts of radiogenic helium. Meanwhile, Cretaceous granites were originated from igneous mantle source materials beneath the Gyeongsang basin, south-eastern area of the Korean peninsula. A presence of mantle components (20Ne/22Ne ≈ 10.13) and/or nucleogenic Ne were identified in some quartz and most biotite samples of granitoids in Jurassic age. Argon isotopic ratios (av. 40Ar/36Ar = 2370) of fluid inclusions in quartz for Jurassic granites are considerably higher than those in Cretaceous granites (av. 40Ar/36Ar = 414), indicating a clear aging effect. He-Ar isotopic signatures together with the characteristics of Nd, Sr, and O isotopes can lead to the conclusion that the generation of Jurassic granitic magma was responsible for the subduction of the Izanagi oceanic plate. Meanwhile, the subduction ridge (e.g., the Kula-Pacific Ridge) model is likely to be a suitable scenario for formation of the Cretaceous granitic magma in the Korean peninsula. [ABSTRACT FROM AUTHOR]

In the western boundary region of Central Iran with Sanandaj-Sirjan, considering the widespread carbonate units in the northeastern Isfahan area, the barite deposits have considerable potential. The Komsheche barite, hosted in the Middle Triassic Shotori dolomite Formation, is the most active mine in the region. Barite mineralization has occurred in two styles, banded-layered and veined-brecciated. Fluid inclusions in the bedded barite homogenize at temperatures from 78 to 122 ºC, with salinity between 10.9 to 17.0 wt.% eq. NaCl, while the homogenization temperature for two-phase inclusions of the second type barite is between 130 to 187 ºC and associated halite-bearing tri-phase inclusions range from 192 to 210 ºC, with an average salinity of 14.3 and 36.6 wt.% eq. NaCl, respectively. The δ34S values of the samples range from 18.40 to 26.34 per mil CDT, and their δ18O values range from 8.9 to 14.7 per mil SMOW. Based on conducted studies, ore-forming fluids were formed in an open and near-bottom seawater system during the early diagenetic stage. The heavy isotope values related to pore water are locked in a closed system during the final stages of diagenetic. Sedimentary type, associated minerals, REE composition, finding of fluid inclusion and isotope reveal that Komsheche barite has the most similarity to diagenetic/cold-seep types of marine barites. Introduction In the western border of Central Iran zone with Sanandaj-Sirjan, according to the extent of carbonate units in the northeastern area of Isfahan, barite deposits have considerable potential. Part of the barytization is formed in the Middle Triassic host rock (such as Komsheche and Lamar) and part in the Lower Cretaceous host rock (such as Pinavand, Bagharabad, Maste-Kouh, Khase-Tarash and east of Mourcheh-Khort), which indicates that these sequences are prone to more discoveries in the future. These barites are unique in terms of sedimentary structure, and the Komsheche deposit is one of the representative examples of strata bound barite deposits in the Triassic sedimentary sequences of this area. Considering that the development of barite mineralization in the Triassic carbonate sequence is still in a halo of ambiguity, in this research, in addition to stratigraphic studies and investigation of the characteristics of mineralization, the mechanism of barite deposition has been tried using the mineralogical studies, the stable isotopes composition, and the fluid inclusions of barite are described. Materials and methods Field surveys were conducted to study ore layers by observing sedimentary characteristics and collecting samples from both host rock and ore. These samples were then analyzed in the laboratory through petrographic and mineralogical studies in the laboratory. Five samples were analysed by ICP-MS at the Zarazma laboratory to quantify major, minor, and rare earth elements. The study of fluid inclusions was conducted using the Linkham THM600 at University of Isfahan. The sulfur and oxygen isotopic composition in the Komsheche deposit was measured using a mass spectrometer. Values of δ34S and δ18O are expressed in parts per thousand or per mil (‰) using the Standard Canon Diablo Troilite (CDT) and Standard Sea Water (SMOW), respectively. Results and discussion The oldest rocks in the Komsheche mining area are assigned to the weathered orange-brown Shotori deposits of the Middle Triassic. These deposits are widespread and have a rough appearance. The lower layer, related to the Sorkh-Shale Formation (Lower Triassic), is not visible in Komsheche. The Nayband Formation, from the Upper Triassic age, consists of coaly shales and dark siltstone with interlayers of quartzitic sandstone. The Jurassic sequence is not visible in the Komsheche area, and no rocks containing Jurassic fossils have been observed in the red conglomerate of the Cretaceous base. The lack of sedimentation from the end of the Late Triassic to the Early Cretaceous may be due to the Cimmerian orogeny. The thin layers of sandstone and red conglomerate at the base of the Lower Cretaceous, with a thickness of up to 2 meters thick, consist of Shotori dolomite and siliceous rocks. This sequence begins without metamorphism but has a sudden change in lithology from clastic to carbonate. In the eastern parts, there is a thick layer of coarse-grained limestone, while the western parts are a sequence of olive-green marls, limestones, and sandy limestones of the Late Cretaceous age with orbitulina and ammonite fossils. Field studies, facies analysis, and laboratory research focusing on shape, mineralogy, texture, and grade indicate that the barite mineralization at the Komsheche mine can be categorized into two main types: banded and veined/brecciated. a) Type 1: The banded facies, which is widespread, contains lower-grade mineral material. It shows a stratification consistent with the host rock, with barite and host rock alternating over a thickness of less than 10 meters and a length of 700 meters. These facies, part of the Shotori dolomite sequence, is the primary mineralized horizon. The presence of interfinger structures of barite and dolomite crystals suggests simultaneous formation in unconsolidated sediments. b) Type II: The veined/brecciated facies, located near the center of the ore deposit, occurs as vein and shear masses formed along reverse faults. This facies represents the high-grade portion of the mine, and it is mined by through open-pit mining. These veins formations are commonly found at the boundary between the Shotori carbonates and the Nayband Formation, with dolomitization and limited silicification in the host rock. Barite veins are typically less than 1.5 meters thick, are surrounded by shear zones less than 2 meters wide. A homogenization temperature (Th) was conducted on 17 primary fluid inclusions (F.I) trapped in barite minerals from both the stratabound and veined/brecciated facies of the Komsheche deposit. The results of the analyzed fluid inclusions are presented in Table 3. In the first type barite, most fluid inclusions are single-phase liquid (L) or two-phase liquid-rich (L>V). The homogenization temperature ranges from 78 to 122 ºC, and the salinity levels range from 10.9 to 17.0 wt.% eq. NaCl. For the second type of barite, the fluid inclusions are predominantly two-phase liquid-rich (L>V), single-phase liquid (L), or three-phase with a solid phase of halite (LVH). The homogenization temperature for the two-phase inclusions of the second type is higher, ranging from 130 to 187ºC, while the three-phase inclusions with halite range from 192 to 210 ºC. The salinity levels for the second type of two-phase inclusions range from 9.5 to 16.0 wt.% eq. NaCl, and for the three-phase inclusions, it ranges from 36.2 to 37.0 wt.% eq. NaCl. The sulfur isotope values (δ34S) of the barite samples range from 18.40 to 26.34 ‰ CDT, while their oxygen isotope values (δ18O) range from 9.8 to 14.7 ‰ SMOW. The sulfur isotope values indicate isotopic diversity. A comparison with previous data (22.6 to 26.7 ‰) reported by (Forghani Tehrani, 2003; Rajabzadeh, 2007) shows differences in the distribution of measured sulfur isotope values, as shown in Table 4. According to the latest diagenetic models, sedimentary barite layers are formed at the sulfate-methane transition zone (SMTZ) during hydrocarbon migration. Based on this study, it was found that barite mineralizing fluids in the initial diagenesis stage were found to have temperatures below 120 ºC and a salinity of about 13 wt.% eq. NaCl. These fluids form near the seafloor in a shallow sea open system where sulfate supply is associated with anaerobic oxidation of methane as a mechanism for the reduction of sulfate to H2S. Barite formation occurs in shallow marine environments through by downward sulfate diffusion and the transfer of hydrocarbons and barium from depth upwards. The periodic formation of barite layers is related to the stability of the SMTZ. In an open system, barite retains the oxygen and sulfur isotope values of the coeval seawater. Barite precipitation occurs by fluid cooling, fluid mixing, and/or water-rock interaction. In the final diagenesis stages, heavy isotope amounts are linked to formation water in closed systems with high water- rock ratios. Veined barite, which is younger, may forms at deeper levels along faults over an extended period, completely replacing the host rock entirely. It is unlikely that veined barite forms near the sea floor. Deep fluids are heating by the geothermal gradient. This research suggests that the barite in question is similar to marine barites found off the coast of Southern California in diagenetic/cold seep environments.

Abstract The study of the fluid inclusions of W–Mo deposits in the mineralization area of Ningshan–Zhen’an , Shaanxi Province, China shows that the gas–liquid two-phase inclusions are mainly present in W–Mo deposits, and the ore-forming fluid can be divided into four types: high-temperature type, middle–high-temperature type, middle-temperature type and low-temperature type. The formation depths of the W–Mo mineralization range from 4.2 to 8.4 km. The boiling and mixing of fluid may have been important mechanisms for the formation of W–Mo mineralization. The skarn-type mineralization is dominated by magmatic water, the quartz-vein-type mineralization includes both magmatic water and meteoric water, and the meteoric water is more involved in the quartz-fluorite-vein-type, beryl-quartz-vein-type and pegmatite-type mineralization. Magma is the main source of sulfur; that is, magma is the main source of mineralization. Combined with the metallogenic setting and geological characteristics of typical ore deposits, in the process of structural system transformation in South Qinling, the ore-forming magma fluid in the Late Indosinian–Yanshanian period was uplifted and emplaced along the NW–WNW direction and NE–NNE direction, and eventually, NW–WNW fault-controlled skarn-type W–Mo mineralization and quartz-vein-type W–Mo deposits accompanied by greisenization, albitization and potash feldspathization formed.

It is of great significance for deep oil and gas exploration to understand the origin and evolution behind overpressure. Overpressure occurs in the deep Shahezi Formation of Xujiaweizi fault depression. However, due to limited degree of exploration, there are some problems in the study area, such as unclear understanding of the origin of overpressure and the vague investigation of overpressure evolution. To clarify the impact of overpressure on oil and gas migration and accumulation in the study area, this study focuses on the research of the origin and evolution of overpressure in the Shahezi Formation of the study area, utilizing single well logging parameters and combining methods such as microthermometry of fluid inclusions, laser Raman spectrum, and basin simulation. The results show that the overpressure of the Shahezi Formation in Xujiaweizi fault depression is primarily generated by hydrocarbon generation pressurization, and the evolution of overpressure is closely related to hydrocarbon generation. The development of overpressure can be divided into two evolutionary stages: early hydrocarbon generation pressurization and late uplift release, with slight variations in different regions. Tight glutenite gas reservoirs in the Shahezi Formation are characterized by continuous charging. The overall charging period ranges from the late Denglouku to the early Mingshui (110‐67 Ma ago). There is an obvious paleo‐overpressure during the gas reservoir formation period. The gas generation period of source rocks occurred approximately 125‐60 Ma ago, and the main gas generation period (112‐67 Ma ago) highly coincides with the period of natural gas charging. The anomalously high pressure during the accumulation period is considered the significant driving force for natural gas charging. In addition, the sustained effect of overpressure provides better conditions for the preservation of tight gas reservoirs within the source. The results of the study are of guiding significance for the in‐depth exploration and development of deep tight sandstone gas in the Shahezi Formation of Xujiaweizi fault depression. [ABSTRACT FROM AUTHOR]

Abnormally high pressures are currently limited and locally developed in the Funing Formation of the Gaoyou Sag, Subei Basin, eastern China, but the paleopressure and its evolutionary history remain unclear. Based on the determination of hydrocarbon charging periods by performing systematic fluid inclusion analysis on sixteen core samples from the Funing Formation, thermodynamic modeling with fluid inclusion data was adopted to reconstruct the paleopressure and redisplay its evolutionary history throughout geological time. Results showed that the Funing Formation experienced two episodes of hydrocarbon charging periods. Episode 1 occurred with the charging of lower maturity oils in the period from 52.8 Ma to 49.5 Ma, which was recorded by yellow-fluorescing oil inclusions. Episode 2 happened with the charging of higher maturity oils in the period from 47.0 Ma to 37.0 Ma, which was characterized by blue-fluorescing oil inclusions. Each episode was an abnormally high-pressured hydrocarbon charging process. The pressure coefficient of Episode 1 reached as high as 1.44, while that of Episode 2 reached as high as 1.40. The current formation pressure is the evolutionary result of paleopressure after a process of rapid increasing and decreasing and slow increasing and is not as high as what it reached during the hydrocarbon charging periods. This work is valuable for the exploration of conventional clastic oil reservoirs and unconventional shale oils in the Funing Formation. [ABSTRACT FROM AUTHOR]

A purification process including flotation separation, acid leaching, calcination, and water quenching was conducted to obtain high-purity quartz sand. The surface morphology of the quartz after flotation separation, acid leaching, calcination, and water quenching reveals that the cracks, pits, and cavities on the quartz surface can be deepened and enlarged, and the more fluid inclusions, the greater the number and openness of cracks, pits, and cavities. The specific surface area is positively correlated with the number of cracks, pits, and cavities, the opacity of quartz glass, and the number of bubbles in quartz glass. The results of Raman spectroscopy analysis reveal that the bubbles in quartz glass are composed of nitrogen, which excludes the possibility of bubble formation in quartz glass caused by the gas composition (i.e., H2O) of unburst fluid inclusions in quartz sand. The formation of bubbles in quartz glass is more likely to be related to a high specific surface area and porosity, which increase the surface adsorption performance of quartz and contribute to the adsorption of more gas. The presented results suggest that using these methods to reduce the content of fluid inclusions in quartz cannot effectively solve the problem of bubbles in quartz glass, and using quartz raw materials with no or minor fluid inclusions is still the key to ensuring the quality of quartz products. [ABSTRACT FROM AUTHOR]

Usually, deep oil and gas accumulation is often controlled by strike–slip faults. However, in the Tarim Basin, deep Ordovician oil and gas accumulations are also found in areas far from the fault zone. The process of oil and gas accumulation in deep reservoirs far from strike–slip fault zones is still unclear at present. The source and evolution of Ordovician fluids were analyzed using inclusion geochemical methods and the U–Pb dating technique. The analysis of rare earth elements and carbon–oxygen–strontium isotopes in the reservoirs showed that the reservoirs were weakly modified by diagenetic fluid. The fluid was derived from the fluid formation during the same period as the seawater, and no oxidizing fluid invaded the reservoir. The late oil and gas reservoirs had good sealing properties. The U–Pb dating results combined with homogenization temperature data revealed that the first-stage oil was charged during the Late Caledonian Period, and the second-stage natural gas was charged during the Middle Yanshanian Period. The evolution of the paleo-pressure showed that the charging of natural gas in the Middle Yanshanian was the main reason for the formation of reservoir overpressure. The strike–slip fault zone was basically inactive in the Middle Yanshanian. During this period, the charged natural gas mainly migrated to the reservoir along the unconformity surface and the open strike–slip fault zone in the upper part of the Ordovician reservoir. The source of the fluid shows that the reservoir in the late stage had good sealing properties, and there was no intrusion of exogenous fluid. The overpressure in the reservoir is well preserved at present. [ABSTRACT FROM AUTHOR]

The study of the fluid inclusions of W–Mo deposits in the mineralization area of Ningshan–Zhen'an , Shaanxi Province, China shows that the gas–liquid two-phase inclusions are mainly present in W–Mo deposits, and the ore-forming fluid can be divided into four types: high-temperature type, middle–high-temperature type, middle-temperature type and low-temperature type. The formation depths of the W–Mo mineralization range from 4.2 to 8.4 km. The boiling and mixing of fluid may have been important mechanisms for the formation of W–Mo mineralization. The skarn-type mineralization is dominated by magmatic water, the quartz-vein-type mineralization includes both magmatic water and meteoric water, and the meteoric water is more involved in the quartz-fluorite-vein-type, beryl-quartz-vein-type and pegmatite-type mineralization. Magma is the main source of sulfur; that is, magma is the main source of mineralization. Combined with the metallogenic setting and geological characteristics of typical ore deposits, in the process of structural system transformation in South Qinling, the ore-forming magma fluid in the Late Indosinian–Yanshanian period was uplifted and emplaced along the NW–WNW direction and NE–NNE direction, and eventually, NW–WNW fault-controlled skarn-type W–Mo mineralization and quartz-vein-type W–Mo deposits accompanied by greisenization, albitization and potash feldspathization formed. [ABSTRACT FROM AUTHOR]

Kadavur is a significant Proterozoic anorthosite-gabbro complex, located within the Madurai block of the southern granulite terrain, India. In Kadavur complex, the marginal zone is made up of rapakivi granites and dolerite dykes and the core of this complex is made up of late-stage intruded pegmatites. Tantalum-niobium (Ta-Nb)-rich pegmatites (n = 20) and barren pegmatites (n = 5) were studied for fluid inclusion and electron paramagnetic resonance (EPR) characterization. Five and two distinct fluid inclusions are identified in the Ta-Nb-rich pegmatites, and barren pegmatites respectively. In the mineralized samples, carbonic inclusions show depression in the CO2 melting temperature indicating the presence of volatile phases of N2, C and CH4, which is also confirmed by a laser Raman microprobe. The similar range of trapping temperatures and different modes of homogenization (liquid and vapour) are attributed to the fluid immiscibility process for Kadavur Ta-Nb mineralization. The EPR is one of the exploration tools for many mineral deposits. EPR spectra signals for mineralized pegmatite and barren pegmatite samples show the paramagnetic induced defect centres of E1 and peroxyl types identified in Kadavur, India. [ABSTRACT FROM AUTHOR]

Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ3⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization. [ABSTRACT FROM AUTHOR]

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Marine deep Ordovician reservoirs are significantly controlled by strike-slip fault zones, which govern reservoir fluid evolution during various activity periods. Such fluid evolution elucidates the process underpinning ultra-deep oil and gas accumulation and delineates the pivotal role of strike-slip fault zones in hydrocarbon aggregation. This method can improve the understanding of the mechanism of hydrocarbon accumulation in deep to ultradeep carbonate rocks. The findings indicate that the Ordovician reservoirs in the northern thrust fault zone of the Fuman Oilfield predominantly exhibit two stages of calcite vein formation. The distribution patterns of rare earth elements and Sr isotope characteristics suggest that both stages of vein formation were sourced from Middle to Lower Ordovician marine strata, with no evidence of oxidizing fluid infiltration. This indicates that late-stage oil and gas charging in deep-ultradeep formations has good sealing properties. In these calcite veins, early-, middle-, and late-stage fluid inclusions were primarily entrapped. By examining the development of primary oil inclusions and combining the U-Pb isotope data of host minerals, this study confirms the occurrence of three stages of oil and gas charging in the deep Ordovician strata of the northern thrust fault zone in the Fuman Oilfield. These stages correspond to approximately 459 ± 7.2 Ma (mid-Caledonian), 348 ± 18 Ma (early Permian), and 268 Ma (late Permian). The key accumulation period of oil and gas reservoirs in the study area is the middle and late Caledonian, and there is a good correspondence between oil and gas charging and fault activity. [ABSTRACT FROM AUTHOR]

The Hongtoushan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the Hunbei granite–greenstone terrane of the North China Craton, has undergone a complex, multi-stage metallogenic evolution. The deposit comprises three main types of massive ores: Type-1 ores, characterized by a sulfide matrix enclosing granular quartz and dark mineral aggregates; Type-2 ores, distinguished by large pyrite and pyrrhotite porphyroblasts and a small amount of gangue minerals; and Type-3 ores, mainly distributed in the contact zone between the ore body and gneiss, featuring remobilized chalcopyrite and sphalerite filling the cracks of pyrite. The metallogenic process of the Hongtoushan deposit is divided into three main stages: (1) an early mineralization stage forming Type-1 massive ores; (2) a metamorphic recrystallization stage resulting in Type-2 massive ores with distinct textural features; and (3) a late-stage mineralization event producing Type-3 massive ores enriched in Cu, Zn, and other metals. This study integrates sulfur isotope, trace elements, and fluid inclusion data to constrain the sources of ore-forming materials, fluid evolution and metallogenic processes of the deposit. Sulfur isotope analyses of sulfide samples yield δ 34 S values ranging from −0.7 to 4.2 (mean: 1.8 ± 1.5, 1 σ), suggesting a predominant magmatic sulfur source with possible contributions from Archean seawater. Trace element analyses of pyrite grains from different ore types reveal a depletion of rare earth elements, Cu, and Zn in Type-2 massive ores due to metamorphic recrystallization, and a subsequent re-enrichment of these elements in Type-3 massive ores. Fluid inclusion studies allowed for identifying three types of ore-forming fluids: Type-1 (avg. T h : 222.9; salinity: 6.74 wt.% NaCl eqv.), Type-2 (avg. T h : 185.72; salinity: 16.56 wt.% NaCl eqv.), and Type-3 (avg. T h : 184.81; salinity: 16.22 wt.% NaCl eqv.), representing a complex evolution involving cooling, water–rock interaction and fluid mixing. This multi-disciplinary study reveals the interplay of magmatic, hydrothermal and metamorphic processes in the formation of the Hongtoushan VMS deposit, providing new insights into the fluid evolution and metallogenic mechanisms of similar deposits in ancient granite–greenstone terranes. [ABSTRACT FROM AUTHOR]

Significant progress has recently been made in deep and ultra-deep oil and gas exploration globally, demonstrating enormous exploration potential of the deep and ultra-deep strata. However, the accumulation and preservation pattern of deep and ultra-deep oil and gas remains poorly understood, greatly impeding further petroleum exploration and development in the deep and ultra-deep strata. By taking the Bozi deep and ultra-deep condensate gas reservoirs in the Kuqa Depression, western China as an example, we attempt to reconstruct the hydrocarbon charge history in such deep reservoirs via an integrated investigation involving quantitative grain fluorescence, fluid inclusion petrography and microthermometry, micro-fluorescence spectroscopy, laser Raman spectroscopy, PVTx modelling, and basin modelling. The results show that: (1) The Bozi deep and ultra-deep reservoirs contain one group of gas inclusion assemblage, and two groups of oil inclusion assemblages, with one being characterized by near yellowish-whitish and blue-whitish diphasic or triphasic oil inclusions, and the other being featured by bright blue diphasic oil inclusions; (2) The first oil charge occurred during the Early Neogene (6.5–5.5 Ma), and the second oil charge occurred during the Late Neogene (4.4–3.5 Ma), under normal hydrostatic pressure or slightly weak overpressure; and (3) The gas charge occurred during the Pleistocene (∼1.6 Ma), with a corresponding reservoir pressure coefficient of approximately 1.7, transforming the reservoir fluid phase state from black oil or volatile oil to condensate gas. Our findings highlight that aside from the present burial depth, a favorable burial history model is crucial for the preservation of liquid hydrocarbons in deep and ultra-deep reservoirs. The occurrence of liquid hydrocarbons in the Bozi deep and ultra-deep condensate gas reservoirs with depths over 7,000 m is benefited from a prolonged period (>100 Ma) of shallow burial and a late-stage (since 10 Ma) rapid subsidence.

The Chazangcuo copper-lead-zinc deposit (hereafter referred to as the Chazangcuo deposit) is situated in the northern portion of the western section of the Gangdese polymetallic metallogenic belt in Tibet, with ore bodies strictly governed by Linzizong Group magmatic rocks and EW-trending faults. This study aims to ascertain the mineralization periods, sources of ore-forming materials, metallogenic physicochemical conditions, and genesis of this deposit. Based on comprehensive field geological surveys, sampling, and microscopic examination of petrological and mineralogical characteristics, we perform qualitative and quantitative geochemical analyses of major elements, trace elements, and rare earth elements (REEs), fluid inclusions, and sulfur and lead isotopes. The findings reveal that the mineralization process of the Chazangcuo deposit can be divided into three periods and four stages: the magmatic-hydrothermal, hydrothermal, and supergene mineralization periods sequentially, which consist of the mineralization stages of quartz-pyrite-sphalerite, medium-low-temperature hydrothermal sulfides, chlorite-carbonate minerals, and supergene oxidation in a chronological order. The ore-forming fluids prove to be medium-low-temperature low-density fluids, and the ore-forming materials are characteristic of upper crustal-derived materials. The ore-forming environment is a medium-low mineralization temperature, a shallow and weakly reducing environment. Overall, the Chazangcuo deposit is identified as a medium-low-temperature magmatic-hydrothermal deposit. The metallogenic model has the vertical zoning characteristics of lead-zinc in the upper part and copper in the lower part.

Objective The Dayingezhuang gold deposit in the middle of the Zhaoping metallogenic belt represents a typical altered-rock type deposit with a giant Au reserve of 283 tons on the Jiaodong Peninsula. The genetic type of the deposit is still controversial. Methods Based on detailed field observations, ore genesis and variations in ore-forming fluids from different depths were investigated in this study. Results Fluid inclusion studies show that the ore-forming fluids formed an H2O-CO2-NaCl±CH4 system with moderate temperature, low salinity, and moderate-low density. Furthermore, the temperatures and salinities decrease gradually from the early to late mineralization stages(Ⅰ-Ⅳ), but the opposite occurs at densities. Hydrogen and O isotopic compositions show that the ore fluids were dominated by magmatic water in the early stage, with subordinate meteoric water input during the late stages. Fluid boiling occurred possibly during the main mineralization stages. Sulfur and Pb isotopes of pyrite indicate that the ore-forming materials were derived from deep crust-mantle mixed magma. Overall, the mineralization process and tectonic setting are similar to those of the other Jiaodong gold deposits in a craton-destruction environment. Conclusion Comprehensive comparisons of ore fluids, Au and Ag contents, and gold fineness between shallow and deep ores show that ore fluids and mineralization intensity are consistent throughout the deposit. Gold precipitation has a broad and stable environment, indicating the great potential for mineral exploration in deep spaces.

A significant breakthrough has been made in the exploration and development of shale oil in the Subei Basin. Cores from well HY1 in the Gaoyou Sag of Subei Basin indicate the presence of well-developed natural fractures within the organic-rich shale of the second member of Paleogene Funing Formation. These fractures contain compelling evidence of shale oil, gas, and fluid activities and migration. This study specifically examines the calcite veins filling the shale fractures within the second member of Funing Formation. Through the integration of methodologies from mineralogy, elemental geochemistry, geochronology, and geological fluid analysis, the originof paleo fluids, the timing of vein formation, and fluid inclusions within the shale fracture veins are investigated. This study also sheds light on paleotemperature conditions and corresponding geological timeframes during the burial, uplift, and denudation of the shale oil-bearing layers. The primary fracture types observed in the second member of Funing Formation include bedding fractures, detachment fractures, shear fractures, shrinkage fractures, and tensile fractures, predominantly filled with fibrous calcite veins indicating a source linked to hydrothermal fluids in a reducing environment. Notably, three distinct stages of shale oil injection are evident within the organic-rich shale fracture veins of the second member of Funing Formation, marked by primary green fluorescent oil inclusions from the Middle Eocene, secondary blue fluorescent oil inclusions from the Late Eocene, and secondary green fluorescent oil inclusions from the Late Quaternary period. The primary accumulation of shale oil occurred during the period of maximum burial depth, emphasizing the significant role of tectonic movements, especially the Sanduo tectonic event, in the redistribution and migration of shale oil in the region.

A-type granites typically exhibit enrichment and mineralization of critical metals such as molybdenum and tin, essential for emerging technologies. However, the key factors influencing their mineralization potential remain elusive. The scarcity of studies on barren systems impedes the understanding of this question. Here, a detailed melt and fluid inclusion study was conducted on the barren Wushan pluton to reconstruct its magmatic evolution and magmatic–hydrothermal transition and explore the factors controlling the metallogenic potential of Mo and Sn in A-type granites. The Wushan pluton displays apparent lithological zoning consisting of two major phases, i.e. medium-grained seriate to porphyritic alkali feldspar granite and fine-grained porphyritic granite. Miarolitic cavities are widely developed in each lithofacies. The silicate melt inclusions from two granitic phases are rhyolitic, with moderate F contents (0.06–0.53 wt %) and depleted H2O contents (2.0–3.5 wt %). Melt inclusions show a wide range of incompatible element contents, such as Cs (9–1977 μg/g) and Rb (268–2601 μg/g), suggesting that Wushan has undergone a high degree of magma evolution. Mo behaves incompatibly in the magmatic evolution, and its content is enriched with the increasing degree of fractional crystallization, but remains constant after the Cs content exceeds 50 μg/g. Rayleigh fractionation model suggests that a large amount of Mo is extracted from fluid exsolution, which restrains Mo from further enrichment. In contrast, Sn behaves as a mildly incompatible element during the entire magmatic evolution history. The contents of Sn increase slowly compared to the trend of Mo, and the maximum contents reach ~30 μg/g in the highly evolved melts. The separation and crystallization of Sn-bearing minerals such as biotite, magnetite, and titanite inhibit the enrichment of Sn. Intermediate-density (ID-type) fluid inclusions hosted in the miarolitic quartz, representing the initial fluid exsolving from magma, display high Mo but low Sn concentrations. Constrained from two assemblages of coexisting ID-type fluid and melt inclusions, the fluid/melt partition coefficients of metals are obtained, with D Mo, fluid/melt at 16–19, while D Sn, fluid/melt is only about 1. The comparison between Mo-mineralized and barren intrusions worldwide shows that the metal contents in melts and fluids are not fundamentally different. The mineralized intrusions are characterized by the lower melt viscosity and the development of apophyses, both of which facilitate the extraction of metals and fluids from large magma chambers, followed by their concentration into a small rock volume. Consequently, it appears that physical and structural conditions rather than chemical compositions play a crucial role in the Mo mineralization process. Enrichment of Sn in melts is necessary but not decisive for Sn mineralization, whereas Sn enrichment in the initial exsolving fluid determines the Sn mineralization potential of a given granitic system. Compared to Sn enrichment in source melting and fractional crystallization which commonly enhance final Sn fertility in the highly evolved melts, the efficiency of Sn partitioning between melt and fluid plays a fundamental role in converting melt fertility into Sn-enriched fluids and thereby high mineralization potential of the magmatic–hydrothermal system. Our findings suggest a prospect for Mo exploration in the coastal A-type granite belt in South China, while the potential for Sn mineralization is expected to be limited. [ABSTRACT FROM AUTHOR]

Guocheng Gold Deposit is located on the northeast margin of Jiaolai Basin. It is composed of Tudui ore section, Shawang ore section, Dongliujia ore section, Longkou ore section, and Houkuang ore section. It is controlled by the detachment structural system dominated by Guocheng fault. The petrography and microscopic temperature measurement of quartz fluid inclusions in the ore show that the fluid inclusions in the deposit can be divided into 3 types: gas-liquid two-phase inclusions, CO2-containing three-phase inclusions, and pure liquid phase inclusions. The salinity of ore-forming fluid is 1.39% -16.53%, and the density is 0.56-1.00 g/cm³. It belongs to medium-low salinity and low- density fluid. The ore-forming temperature is 200°C-360°C, and the pressure of ore-forming fluid is 60-125 MPa. The ore-forming depth is 6.22-9.31 km. Based on predecessors' research achievements, it is considered that the genesis of Guocheng Gold Deposit is a mesothermal hydrothermal vein type deposit, of which the mineralization involves mantle fluid, controlled by the detachment structural system dominated by Guocheng fault. [ABSTRACT FROM AUTHOR]

Copyright of Acta Petrologica et Mineralogica / Yanshi Kuangwuxue Zazhi is the property of Acta Petrologica et Mineralogica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Kiruna-type iron oxide-apatite (IOA) and iron oxide copper-gold (IOCG) deposits are commonly spatially and temporally associated with one another and coeval host magmatism. The Zanjan area in the Tarom-Hashtjin metallogenic province (THMP) in NW Iran hosts several iron oxide deposits that exhibit a close spatial and temporal relationship with Upper Eocene granitoids. Here, using fluid inclusion, mineralogy, and hydrothermal alteration data from the Chore-Nab iron oxide deposit in combination with other deposits, a new genetic model is developed to explain the formation of the iron oxide mineralization. Furthermore, evidence of an IOA-IOCG transition ore system (IO ± A) in this province is presented. The Chore-Nab orebodies have undergone sodic (albite) alteration associated with an early mineralization stage followed by calcic-sodic (actinolite-rich) alteration related to the formation of a second mineralization stage. The process was finally completed by late veinlets of chalcopyrite, which are related to potassic alteration. Fluid inclusion data show that the initial oreforming fluids (liquid-vapor- and liquid-vapor-solid)-type inclusions of disseminated ore) have an average temperature and salinity of 403 °C, 14.2 wt.% NaCl equiv., and 371 °C, 44.9 wt.% NaCl equiv., respectively. The temperature and salinity of fluids decreased to an average of 277 °C and 8.9 wt.% NaCl equiv. during the formation of magnetite and magnetite-actinolite veins (LV-type inclusions). Subsequently, the values dropped to an average of 266 °C and 5.3 wt.% NaCl equiv. from late chalcopyrite veinlets (LV-type inclusions). These temperature and salinity values indicate a magmatic-hydrothermal ore system. Dilution and cooling of the hot magmatic-hydrothermal metalliferous fluid by mixing with meteoric fluids may have been the main mechanisms responsible for the deposition of metals transported as metal chloride complexes. A decrease in temperature and apatite content, as well as an increase in Cu content is observed from southeastern Sorkhe-Dizaj deposit (massive magnetite + apatite) to the northwest Chore-Nab deposit in the Zanjan area. The dominant element association in the Chore-Nab deposit (Fe) differs from IOCG (Fe-Cu-Au) and IOA (Fe-P) deposits. These results reveal that IOA deposits (e.g., Sorkhe-Dizaj) were formed along deep-seated crustal faults and ascending fluids, which transported Fe and minor Cu to intermediate levels of the system. Therefore, magnetite and sulfides precipitated to form the Chore-Nab IO ± A deposit. This model explains the transition of IOA-IOCG deposits within the same area, providing a valuable conceptual framework to define further exploration strategies in the Tarom-Hashtjin metallogenic province and elsewhere. [ABSTRACT FROM AUTHOR]

In the western boundary region of Central Iran with Sanandaj-Sirjan, considering the widespread carbonate units in the northeastern Isfahan area, the barite deposits have considerable potential. The Komsheche barite, hosted in the Middle Triassic Shotori dolomite Formation, is the most active mine in the region. Barite mineralization has occurred in two styles, banded-layered and veined-brecciated. Fluid inclusions in the bedded barite homogenize at temfaatures from 78 to 122 ºC, with salinity between 10.9 to 17.0 wt.% eq. NaCl, while the homogenization temfaature for two-phase inclusions of the second type barite is between 130 to 187 ºC and associated halite-bearing tri-phase inclusions range from 192 to 210 ºC, with an average salinity of 14.3 and 36.6 wt.% eq. NaCl, respectively. The δ34S values of the samples range from 18.40 to 26.34 fa mil CDT, and their δ18O values range from 8.9 to 14.7 fa mil SMOW. Based on conducted studies, ore-forming fluids were formed in an open and near-bottom seawater system during the early diagenetic stage. The heavy isotope values related to pore water are locked in a closed system during the final stages of diagenetic. Sedimentary type, associated minerals, REE composition, finding of fluid inclusion and isotope reveal that Komsheche barite has the most similarity to diagenetic/cold-seep types of marine barites. IntroductionIn the western border of Central Iran zone with Sanandaj-Sirjan, according to the extent of carbonate units in the northeastern area of Isfahan, barite deposits have considerable potential. Part of the barytization is formed in the Middle Triassic host rock (such as Komsheche and Lamar) and part in the Lower Cretaceous host rock (such as Pinavand, Bagharabad, Maste-Kouh, Khase-Tarash and east of Mourcheh-Khort), which indicates that these sequences are prone to more discoveries in the future. These barites are unique in terms of sedimentary structure, and the Komsheche deposit is one of the representative examples of strata bound barite deposits in the Triassic sedimentary sequences of this area. Considering that the development of barite mineralization in the Triassic carbonate sequence is still in a halo of ambiguity, in this research, in addition to stratigraphic studies and investigation of the characteristics of mineralization, the mechanism of barite deposition has been tried using the mineralogical studies, the stable isotopes composition, and the fluid inclusions of barite are described. Materials and methodsField surveys were conducted to study ore layers by observing sedimentary characteristics and collecting samples from both host rock and ore. These samples were then analyzed in the laboratory through petrographic and mineralogical studies in the laboratory. Five samples were analysed by ICP-MS at the Zarazma laboratory to quantify major, minor, and rare earth elements. The study of fluid inclusions was conducted using the Linkham THM600 at University of Isfahan. The sulfur and oxygen isotopic composition in the Komsheche deposit was measured using a mass spectrometer. Values of δ34S and δ18O are expressed in parts fa thousand or fa mil (‰) using the Standard Canon Diablo Troilite (CDT) and Standard Sea Water (SMOW), respectively. Results and discussionThe oldest rocks in the Komsheche mining area are assigned to the weathered orange-brown Shotori deposits of the Middle Triassic. These deposits are widespread and have a rough appearance. The lower layer, related to the Sorkh-Shale Formation (Lower Triassic), is not visible in Komsheche. The Nayband Formation, from the Upfa Triassic age, consists of coaly shales and dark siltstone with interlayers of quartzitic sandstone. The Jurassic sequence is not visible in the Komsheche area, and no rocks containing Jurassic fossils have been observed in the red conglomerate of the Cretaceous base. The lack of sedimentation from the end of the Late Triassic to the Early Cretaceous may be due to the Cimmerian orogeny. The thin layers of sandstone and red conglomerate at the base of the Lower Cretaceous, with a thickness of up to 2 meters thick, consist of Shotori dolomite and siliceous rocks. This sequence begins without metamorphism but has a sudden change in lithology from clastic to carbonate. In the eastern parts, there is a thick layer of coarse-grained limestone, while the western parts are a sequence of olive-green marls, limestones, and sandy limestones of the Late Cretaceous age with orbitulina and ammonite fossils.Field studies, facies analysis, and laboratory research focusing on shape, mineralogy, texture, and grade indicate that the barite mineralization at the Komsheche mine can be categorized into two main types: banded and veined/brecciated. a) Type 1: The banded facies, which is widespread, contains lower-grade mineral material. It shows a stratification consistent with the host rock, with barite and host rock alternating over a thickness of less than 10 meters and a lenth of 700 meters. These facies, part of the Shotori dolomite sequence, is the primary mineralized horizon. The presence of interfinger structures of barite and dolomite crystals suggests simultaneous formation in unconsolidated sediments. b) Type II: The veined/brecciated facies, located near the center of the ore deposit, occurs as vein and shear masses formed along reverse faults. This facies represents the high-grade portion of the mine, and it is mined by through open-pit mining. These veins formations are commonly found at the boundary between the Shotori carbonates and the Nayband Formation, with dolomitization and limited silicification in the host rock. Barite veins are typically less than 1.5 meters thick, are surrounded by shear zones less than 2 meters wide.A homogenization temfaature (Th) was conducted on 17 primary fluid inclusions (F.I) trapped in barite minerals from both the stratabound and veined/brecciated facies of the Komsheche deposit. The results of the analyzed fluid inclusions are presented in Table 3. In the first type barite, most fluid inclusions are single-phase liquid (L) or two-phase liquid-rich (L>V). The homogenization temfaature ranges from 78 to 122 ºC, and the salinity levels range from 10.9 to 17.0 wt.% eq. NaCl. For the second type of barite, the fluid inclusions are predominantly two-phase liquid-rich (L>V), single-phase liquid (L), or three-phase with a solid phase of halite (LVH). The homogenization temfaature for the two-phase inclusions of the second type is higher, ranging from 130 to 187ºC, while the three-phase inclusions with halite range from 192 to 210 ºC. The salinity levels for the second type of two-phase inclusions range from 9.5 to 16.0 wt.% eq. NaCl, and for the three-phase inclusions, it ranges from 36.2 to 37.0 wt.% eq. NaCl.The sulfur isotope values (δ34S) of the barite samples range from 18.40 to 26.34 ‰ CDT, while their oxygen isotope values (δ18O) range from 9.8 to 14.7 ‰ SMOW. The sulfur isotope values indicate isotopic diversity. A comparison with previous data (22.6 to 26.7 ‰) reported by (Forghani Tehrani, 2003; Rajabzadeh, 2007) shows differences in the distribution of measured sulfur isotope values, as shown in Table 4.According to the latest diagenetic models, sedimentary barite layers are formed at the sulfate-methane transition zone (SMTZ) during hydrocarbon migration. Based on this study, it was found that barite mineralizing fluids in the initial diagenesis stage were found to have temfaatures below 120 ºC and a salinity of about 13 wt.% eq. NaCl. These fluids form near the seafloor in a shallow sea open system where sulfate supply is associated with anaerobic oxidation of methane as a mechanism for the reduction of sulfate to H2S.Barite formation occurs in shallow marine environments through by downward sulfate diffusion and the transfer of hydrocarbons and barium from depth upwards. The faiodic formation of barite layers is related to the stability of the SMTZ. In an open system, barite retains the oxygen and sulfur isotope values of the coeval seawater. Barite precipitation occurs by fluid cooling, fluid mixing, and/or water-rock interaction.In the final diagenesis stages, heavy isotope amounts are linked to formation water in closed systems with high water- rock ratios. Veined barite, which is younger, may forms at deefa levels along faults over an extended faiod, completely replacing the host rock entirely. It is unlikely that veined barite forms near the sea floor. Deep fluids are heating by the geothermal gradient. This research suggests that the barite in question is similar to marine barites found off the coast of Southern California in diagenetic/cold seep environments. AcknowledgementsPart of the information of this research has been extracted from the master's thesis project of the first author. Financial support was provided by University of Isfahan. We also acknowledge logistic support by the Falat-e Iran Barite Company. [ABSTRACT FROM AUTHOR]

Jinchanghe is a Zn-Pb-Fe-Cu skarn deposit in the northern Baoshan block, southwestern China. It is a typical distal skarn deposit with orebodies in the Cambrian Hetaoping Formation limestone and calcareous siltstone. The skarn minerals display a vertical zonation with garnet skarn in the lower part and pyroxene skarn in the upper part. Economic metals are also zoned with Fe at the base, Cu in the middle, and Zn-Pb in the upper part. The skarn formation and Zn-Pb-Fe-Cu mineralization is divided into four paragenetic stages: a pre-ore stage dominated by prograde garnet and pyroxene, an oxide stage represented by Fe mineralization associated with retrograde ilvaite, actinolite and epidote alteration, a sulfide stage characterized with Cu–Zn-Pb sulfides, and a post-ore stage with barren calcite, quartz and chlorite. Fluid inclusion microthermometry indicates that the hydrothermal fluids of the Jinchanghe skarn system evolved from the pre-ore stage (450–480 °C and 11.7–15.5 °C wt% NaCl equiv), through the oxide stage (230–280 °C and 6.5–12.2 wt% NaCl equiv), the sulfide stage (190–230 °C and 1.3–10.3 wt% NaCl equiv), and eventually to the post-ore stage (120–180 °C and 1.6–4.6 wt% NaCl equiv). Correspondingly, the δ18Ofluid values decrease from 1.8–7.1‰ to 1.0–6.4‰, -1.0 to 1.3‰, and -3.6 to -1.4‰. This indicates that the pre-ore fluids comprise a magmatic component but mixed with some meteoric water, and in the later stages meteoric water has become dominant in the hydrothermal system. Zinc and sulfur isotope compositions reveal that the Zn and S forming the sulfides have a dominantly magmatic origin. The coupled decreases of fluid temperature, salinity, and δ18Ofluid values during the mineralization indicate simultaneous mixing with meteoric water and ore precipitation, suggesting that fluid mixing was critical in ore deposition. The gradual increase of δ13CCO2 values in equilibrium with the hydrothermal calcite (-5.2 to -1.6‰) from the sulfide stage to the post-ore is attributed to the reaction between the fluids and the carbonate wallrocks, implying a role that fluid-rock interaction has taken in the sulfide deposition. Fluid mixing and fluid-carbonate reaction are the two major factors controlling the formation of the Jinchanghe deposit. [ABSTRACT FROM AUTHOR]

Fluid inclusions in stalagmites are becoming increasingly important for paleoclimate research. Within this framework, noble gas thermometry, based on noble gases dissolved in water from fluid inclusions, provides quantitative estimations of cave air paleotemperature. Two major issues of Noble Gas Temperature (NGT) determination on speleothems are (1) the potential lack of enough water for the analysis and (2) the presence of trapped gas not dissolved in water that can be released during the analysis from biphasic or all-gas fluid inclusions, as its contribution to the bulk noble gas signal can hinder NGT results. Although the step-crushing method helps to reduce the second issue, it also decreases the amount of water available for the calculations. In order to obtain reliable NGT results with low uncertainties, a major challenge is still to reach a balance between sufficient water for analysis and a small amount of "atmospheric" gas. The difficulty is that the extraction process cannot be standardized since it strongly depends on the type of sample. The objective of this work is to investigate how the characteristics of the speleothem can determine the adequacy of the extraction process. For this purpose, we consider a stalagmite from a Mediterranean cave that consists of columnar elongated calcite and contains a significant quantity of fluid inclusions, which suggests good potential for NGT analysis. Results, however, were poorly satisfactory. Trying to understand the source of the problems, an integrated study of petrography and petrophysical features was performed. The samples were found to be different depending on the stage of coalescence of crystals and thus separated into "open" and "closed" fabrics. Classic petrographic analysis and non-destructive (nuclear magnetic resonance) techniques were used to characterize the type and amount of fluid inclusions present in both types of fabrics. The study indicates that the closed fabric (total coalescence of calcite crystals) has most water trapped in water-filled, small intracrystalline fluid inclusions that usually contain very little gas. This fabric is very suitable for NGT determination, but since the amount of water is quite small, the sample should be crushed in only one step with a large number of beats to break all the inclusions. In contrast, samples with open fabric (partial coalescence of calcite crystals) contain a higher amount of water and, also, gas-filled large intercrystalline fluid inclusions. For this fabric, step-crushing of the sample is necessary. However, the low amount of water left for the second and third crushings could lead to flawed NGT results. Thus, we suggest modifying the method to get rid of part of the gas in the first crushing while leaving enough water for the following steps. This work shows the importance of characterizing speleothems and fluid inclusions, including their petrography and petrophysical characteristics, before starting NGT analysis, allowing the selection of the most favorable samples and the customization of the step-crushing procedure. [ABSTRACT FROM AUTHOR]

Skarn Au deposits exist in the circum-pacific metallogenic belt. Interestingly, the Da'anhe Au deposit is the only independent skarn gold deposit in the Lesser Xing'an Range. To determine the metallogenic mechanism and prospecting potential of the Da'anhe deposit, we performed skarn mineralogy, fluid inclusion (FI) and H-O isotope analyses. The results show the following: (1) The Da'anhe deposit is a calcareous reduced skarn Au deposit that formed between an Early Jurassic gabbroic diorite and the Permian Tumenling Formation marble. Its metallogenic process includes five stages: the early skarn stage (Stage I1), late skarn stage (Stage I2), early quartz-sulfide stage (Stage II1), late quartz-sulfide stage (Stage II2) and quartz-carbonate stage (Stage II3). Gold precipitated in Stage II1 and Stage II2. (2) The initial ore-forming fluid was derived from magmatic water and featured a high temperature and intermediate to high salinity. After boiling and mixing, the fluid eventually changed to a low-temperature and low-salinity reducing fluid dominated by meteoric water. (3) The formation depth of the Au orebodies was 2.27–3.11 km, and the orebodies were later lifted to the surface (<500 m). The potential for finding skarn Au deposits in the study area is limited. (4) The distinctive nature of the ore-related magma (i.e., source, reducing conditions and high water content) was key to the formation of the Da'anhe skarn gold deposit. [ABSTRACT FROM AUTHOR]

Petrological, geochemical and zircon U–Pb and Hf isotope studies were carried out on the Hajseyran pluton, along the Tarom–Hashtjin metallogenic zone, as part of the Alborz–Azerbaijan magmatic belt, which is located in the central part of the Alpine–Himalayan orogenic belt. The Hajseyran pluton, which is made up of syenite, monzonite, quartz-monzonite and granite, yields a zircon U–Pb age of 39.20 ± 0.56 Ma (for a quartz-monzonite sample) with shoshonitic features. Enrichment in large ion lithophile elements, depletion in high-field-strength elements and negative anomalies of Nb, Ta and Ti in Chomalou samples suggest a subduction-related arc magmatic setting. The Chomalou epithermal Pb–Zn–Cu deposit occurs close to the Hajseyran pluton with the quartz–base metal sulfide veins predominantly hosted by Eocene volcanic rocks. The ore-forming processes include chalcopyrite and sphalerite–galena formation, with the latter the major mineralisation in this region. Microthermometric results from the liquid–vapour fluid-inclusion assemblages show that the homogenisation temperatures in the first-stage quartz range from 230 to 310 °C, in the sphalerite and second-stage quartz from 161 to 293 °C and in the late-stage quartz from 175 to 262 °C. The salinities of fluids decrease from early-stage quartz to late-stage quartz. The calculated stable isotope values of ore–fluid components (δ18Owater = +3.28‰ to −3.68‰; δ34SH2S = +5.5‰ to +7.8‰) show that magmatic fluids have played a significant role during mineralisation. The Chomalou deposit is interpreted as a volcanic-hosted intermediate-sulfidation type of epithermal mineralisation formed through shallow-level emplacement of the Hajseyran pluton, which formed via partial melting of phlogopite–amphibole-bearing sub-continental lithospheric mantle. The Neotethyan slab roll-back and concomitant asthenospheric upwelling led to the decompression melting of metasomatised sub-continental lithospheric mantle and the formation of several K-rich plutons and associated epithermal deposits in the Alborz–Azerbaijan magmatic belt. The late Eocene Hajseyran pluton shows a shoshonitic, arc-related signature. The Chomalou Pb–Zn–Cu deposit is an intermediate-sulfidation style of epithermal mineralisation. Fluid inclusion and stable isotope data suggest the evolution of ore-fluid system from magmatic to meteoric. Decompression melting of metasomatised sub-continental lithospheric mantle via slab roll-back led to the formation of Hajseyran pluton. [ABSTRACT FROM AUTHOR]

CO2 and N2 are important gas components of deep-sourced geological fluids. To establish a quantitative method for the study of these fluids, we used a high-pressure optical cell, a heating–cooling stage, and a laser Raman spectrometer to examine pure CO2 and N2 gases and nine CO2-N2 gaseous mixtures at 24–300°C and 2–40 MPa. The results show that the CO2 Fermi diad split and the peak area ratios of the ν1 band of N2 to the upper band of CO2 are considered to be the best for determining pressure and composition, respectively. The quantitative Raman analysis method developed in this study for the determination of the CN2/CCO2 molar ratio was verified by measuring those in synthetic N2-CO2-H2O fluid inclusions. The developed method has also been applied to the analysis of natural fluid inclusions in quartz from Donghai for the determination of both the CN2/CCO2 molar ratio and pressure. [ABSTRACT FROM AUTHOR]

Introduction: The Niaz Cu prospect is located 25 km west of Meshkinshahr, east of the Qaradagh metallogenic zone. The intrusion Oligo-Miocene magmatic bodies into the Paleocene-Eocene rock units has led to alteration and mineralization. The rock units of this area include batholiths Ι and ΙΙ (Khanbaz granodiorite and Khankandi granodiorite), Niaz quartz-monzonite/quartz-monzodiorite and ore-bearing rhyodacite breccia. Materials and Methods: In this research, the geological features, alteration, mineralization and physicochemical conditions of mineralizing fluids have been studied. In this regard, sampling from altered, mineralized zones and drilling cores were carried out and 23 samples were analyzed by XRF and 18 samples by ICP-OES methods and microthermometric measurements were performed on 8 doubly-polished thin sections. Results and Discussion: The intrusive units have high-K calc-alkaline to shoshonitic nature, and the geochemical characteristics of their trace elements indicate similarities with subduction-related magmas. The negative anomaly of Ti and Nb in these rocks can be due to the magmatism related to the subduction processes, as well as the stability of the phases containing these elements during partial melting or their separation during the differentiation process. The enrichment of Pb, La, K, U, and Th elements and the depletion of Sr, Ti, and Nb can be attributed to crustal contamination. Hypogene alterations at Niaz include potassic, phyllic, propylitic and intermediate argillic types. Mineralization has occurred during early, middle, and late stages. Based on the mineralogy and paragenetic sequence, at least five types of veins/veinlets can be distinguished in Niaz deposit. Group A veinlets contain quartz+pyrite+chalcopyrite+magnetite, group B veins are also present in the potassic and phyllic alteration zones, veinlets of group C are mainly formed in the middle stage of mineralization, group D veins are mostly observed in the phyllic alteration zone, which are formed in the middle and later stages of hydrothermal activities and group E veins are almost devoid of sulfide minerals and mainly contain bright-color minerals (quartz and/or calcite)±tourmaline and are mostly present in the propylitic alteration zone. Studies on fluid inclusions (FIs) within the quartz veinlets showed that there are four types of FIs at room temperature, (1) mono-phase vapor, (2) liquidrich 2-phase, (3) vapor-rich 2-phase, and (4) multi-phase solid containing daughter solid phases. The ranges of FIs are about 280-360°C in the potassic, 280-360°C and 280-300°C in phyllic and 170-330°C in propylitic alteration zones. Conclusion: The petrology and petrogenesis of magmatic host rocks, mineralogy, hydrothermal alteration in the Niaz area testify to a porphyry-type Cu mineralization. The main sulfide mineralization includes vein-type pyrite, molybdenite, chalcopyrite, sphalerite and galena. Fluid inclusion microthermometry results show a Th range of 170-360 °C and salinity values of 0.2-60 wt%NaCl equiv., corresponding to the ranges of porphyry Cu deposits. Boiling and simple colling of ore-bearing fluids were the main processes for ore precipitation. [ABSTRACT FROM AUTHOR]

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Twangiza-Namoya Gold Deposit within the Kibaran Belt of the Democratic Republic of the Congo represents a crucial manifestation of the hydrothermal gold system. This review investigates its intricate origin and the subsequent metallogenic evolution that has shaped its present-day characteristics and offers a systematic categorization based on its deposition processes and geotectonic settings. The findings reveal that the gold deposits are predominantly derived from sedimentary fluid sources. Within this vast metallogenic province, two stages of gold deposition have been constrained: (a) the early-stage formation related to the accretion of Rodinia assembly with subduction-collisional event where diagenesis cemented the syngenetic pyrite carbonaceous sediments and (b) the later stage deposition related to the continent-collisional event during the last stage of Rodinia supercontinent amalgamation. Previous isotopic investigations, with a particular emphasis on pyrite sulfur isotopes on both host rocks and vein-bearing sulfides, have been instrumental in tracing the origins of gold-bearing fluids in the study region. The isotopic variance in the four deposits: Twangiza (−5.2 % to +3 %, avg. −0.3 %), Kamituga (−0.6 % to −0.9.1 %, avg. −5%), Lugushwa (+3.0 % to −18.4 %), and Namoya, on the southernmost end, has a vast range but with much heavier isotope compositions, ranging between +1.3 % and to +22.6 %, with an average of +12.2 %. The data predominantly points to the sedimentary origins of ore fluids in the Twangiza-Namoya Gold belt, highlighting the pivotal role of sedimentary processes in shaping the metallogenic landscape of the region. The fluids inclusions depicted the deposits to be formed from H2O-Nacl-H2O with abundant CH4 and N2 ore-forming fluid, moderate temperature (350–500 °C), and low salinity. The overall results confirm the genetic style of the Twangiza-Namoya Gold Belt to be an orogenic gold-style deposit that was emplaced during the early Neoproterozoic era in low greenschist facies terrain.

The Panzijian gold deposit is located in the Jiaobei uplift on the eastern margin of North China Craton. It is a quartz vein-type gold deposit in the southern end of the Qixia-Penglai ore belt. In order to explore the source and properties of ore-forming fluids and materials in the Panzijian gold deposit, explore the ore-forming process and reveal the genesis of the deposit, this work has carried out petrographic observation and temperature measurement of gold-bearing quartz fluid inclusions, laser Raman experiment, gold-bearing quartz H–O isotope study, and gold-bearing pyrite Pb isotope study. The Panjian gold deposit is divided into four metallogenic stages and the metallogenic stage Ⅲ is the main gold mineralization stage. Fluid inclusions show that the ore-forming fluids at the Panzijian gold deposit belong to a CO2–H2O–NaCl system with low temperature (172–341 °C), salinity (1.57–10.49 wt% NaCl), and density (0.79–0.96 g/cm3). Gold-bearing Quartz H–O isotopic data (δD = −79.8 to −65.1‰, δ18OH2O = 1.33–2.63‰) show that the ore-forming fluid was derived from the mixing of magmatic water and meteoric water. Gold-bearing Pyrite Pb isotopes with crustal signature (206Pb/204Pb = 16.06–16.943, 207Pb/204Pb = 15.337–15.858, 208Pb/204Pb = 37.143–38.081, and 206Pb/207Pb = 1.025–1.105) support that some ore-forming materials were crust-derived. We proposed a metallogenic model for the Panzijian gold deposit: Stress transition of Jiaobei uplift tectonic system inducing asthenospheric upwelling. The lithostatic pressure dropped and fluids were exsolved from the magma. The ore-forming fluid ascended along local faults and the pressure further dropped, resulting in fluid immiscibility and gold deposition along structural traps (e.g., faults).

Abstract Abiotic synthesis of hydrocarbon-bearing fluids during geological processes has a significant impact on the evolution of both the Earth's biosphere and the solid Earth. Aqueous alteration of ultramafic rocks, i.e., serpentinization, which forms serpentinite, is one of the geological processes generating abiotic methane (CH4). However, abiotic CH4 generation is not limited to the serpentinization of mafic and ultramafic lithologies. Metasedimentary dolomitic marble from the Hida Belt, Japan, is characterized by the presence of forsterite-rich olivine (Fo~89–93), and olivine crystals contain abundant fluid inclusions (

Objective Lead-zinc mineralization is widely distributed in southwestern Hubei Province, but no large deposits have been found thus far, and there is a lack of systematic studies on metallogenic systems. Methods The C-H-O-S-Pb isotope analysis and the homogenization temperature of fluid inclusions of lead-zinc-fluorite ore in the Geleche area of Laifeng were conducted. Results The results show that the homogenization temperature of fluid inclusions in fluorite and calcite is concentrated between 137-170℃, and the variation range of salinity is 11.46%-16.89%. It is a NaCl-H2O system with low temperature and medium and low salinity. The main source may be metamorphic dehydration of rock formations containing sedimentary sulfate (marine sediments). The δ34S content ranges from 9.5‰ to 11.8‰, with an average of 10.92‰. 206Pb/204Pb < 18.20, 207Pb/204Pb>15.60, and 208Pb/204Pb < 39.00, and the floating ratio is small and high μ and high ω. Conclusion The sulfur and lead sources are mainly from the Ordovician and Cambrian ore-bearing strata in the Paleozoic sedimentary basin of the upper crust. Syngenetic sedimentary diagenesis and epigenetic medium- and low-temperature hydrothermal transformation are the dominant genetic types of the Geleche mining area. Compared with the typical lead-zinc deposits in the Yangtze Platform of West Hubei and Hunan, they have great similarity and obvious differences in metallogenic fluid, Paleozoic sedimentary environment and tectonic background.

Objective Commercial oil accumulation in the Jinghe Oilfield of the Southwest Ordos Basin was primarily found in the Northeast area. Previous studies have shown that oil mainly sourced from the oil shale in Member 7 of the Yanchang Formation. However, whether the oil comes from the source rocks spatially located in the Jinghe Oilfield or the basin center has not been determined, which inhibits further exploration of the Jinghe Oilfield. Methods In this paper, the hydrocarbon generation and expulsion history of source rocks in Member 7 of the Yanchang Formation in different tectonic parts of the Jinghe Oilfield and in the basin center have been reconstructed through basin simulation. Then, the accumulation periods of oil in the Yanchang Formation reservoir have been identified using fluid inclusion technology. Results The time window comparison of the oil accumulation in reservoir and the hydrocarbon generation and expulsion of source rocks show that oil in the Jinghe Oilfield limitedly came from the source rocks beneath the Jinghe Oilfield but more widely came from source rocks in the basin center. The oil in the Jinghe Oilfield generally shows the migration direction from Northeast to Southwest. Conclusion Therefore, unlike the traditional model of short-distance vertical migration, a new model can be established as that, the oil in the Jinghe Oilfield mainly laterally migrated from the hydrocarbon kitchen in the basin center along the strike-slip fault belt. The research results can provide an important reference for the prediction of hydrocarbon accumulation zones in the Jinghe Oilfield.

The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be 122.1±6.4 Ma, 14.4±1.0 Ma –14.2±0.3 Ma. The hydrocarbon charging events occurred at around 14.2–30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.

Abiotic synthesis of hydrocarbon-bearing fluids during geological processes has a significant impact on the evolution of both the Earth's biosphere and the solid Earth. Aqueous alteration of ultramafic rocks, i.e., serpentinization, which forms serpentinite, is one of the geological processes generating abiotic methane (CH4). However, abiotic CH4 generation is not limited to the serpentinization of mafic and ultramafic lithologies. Metasedimentary dolomitic marble from the Hida Belt, Japan, is characterized by the presence of forsterite-rich olivine (Fo~89–93), and olivine crystals contain abundant fluid inclusions (<1 to 10 μm in size). Raman spectroscopic analyses of olivine-hosted fluid inclusions found that both primary and secondary fluid inclusions contain CH4, lizardite/chrysotile, and brucite. This indicates that micro-scale interactions between COH fluid and host olivine produced CH4 through the reduction of CO2 by H2 released during local serpentinization within inclusions. Our observation implies that the dolomitic marble has the potential to be a key lithology for the synthesis and storage of abiotic CH4 in a shallower crustal portion of orogenic belts. [ABSTRACT FROM AUTHOR]

Jinying Gold Deposit is situated on the eastern section of the northern margin of China-Korea quasi-platform. It lies on the depression side of the contact interface between Tieling-Jingyu uplift and Taizihe-Hunjiang depression fold fault bundle. Through field investigation, mineralogical analysis, electron probe, and fluid inclusion testing, it has been determined that the deposit’s mineral composition is uncomplicated and consists of siliceous structural breccia-type ore. The gold mineral species include native gold, silver-bearing native gold, and electrum, with quartz being the primary host for gold which occurs mainly as fissure gold, followed by intergranular and encased gold. The inclusions within quartz consist primarily of gas-liquid two-phase fluids, which take on a predominantly oval, diamond and irregular form. Ore formation occurs at temperatures ranging from 139.6 ℃ to 253.1 ℃,with salinity levels between 1.74 % and 4.65 %,densities ranging from 0.79 g/cm³ to 0.94 g/cm³, pressures between 33.6 MPa and 65.6 MPa, and depths of formation spanning from 1.2 km to 2.4 km; these characteristics classify the fluid as medium-low temperature, low salinity, and low density. [ABSTRACT FROM AUTHOR]

Magnetite mineralization accompanied by minor hematite, pyrite, chalcopyrite, tetrahedrite, tennantite, and goethite, occurs in the Guydash iron skarn deposit in East Azarbaijan province, Iran. Geologically, it is located in the northwestern part of the Sanandaj–Sirjan zone. The skarn was formed by the intrusion of igneous bodies, especially porphyritic diorites, in contact with Middle-Upper Jurassic limestones and lesser Eocene pyroclastics. During skarn formation, four paragenetic stages of mineralization are distinguished: the prograde, retrograde, sulfidic and supergene stages, with magnetite deposited in the retrograde stage. Microthermometric data from fluid inclusions in calcite and quartz showed that the retrograde mineralization stage occurred at low to moderate temperatures (159.7–299.5 °C), a maximum pressure of 95 bar, and a maximum depth of 1 km. The fluids responsible for mineralization in this stage were aqueous and had low to high salinity (2–34 wt% NaCl equivalent). Fluid inclusion data indicate that the mineralizing fluid in the Guydash deposit was derived from a mixture of magmatic, meteoric, basinal, and metamorphic waters. The δ18O values in magnetite range from + 5.8 to + 10.2‰. The δ18O values of water in equilibrium with magnetite at an average homogenization temperature of 230 °C were calculated to range from -2.43‰ to 1.97‰. The O isotope values in magnetite revealed that the mineralizing fluids were mainly from magmatic waters. The δ34S values in pyrite from sulfidic stage range from + 10.2 to + 12.6‰, indicating that the sulfur was supplied from seawater sulfate source. Geological, mineralogical, fluid inclusion and isotopic data suggest that the Guydash deposit is a typical calcic-type Fe skarn deposit related to the intrusion of dioritic rocks into the Jurassic limestones. [ABSTRACT FROM AUTHOR]

We provide new constraints for the fluid flow system at the origin of two F-Ba deposits located at the unconformity between the south of the Paris Basin and the northern edge of the French Massif Central. We used microthermometry and bulk crush-leach analyses to determine isotope ratios of mineralizing fluids (δ18O, δD, δ37Cl), together with cation and anion composition of fluid inclusions hosted by fluorite. Chlorinity and Cl/Br molar ratios (212–521) indicate the involvement of a brine, whose origin likely corresponds to Triassic evaporated seawater compatible with supratidal dolomitic facies preserved nearby. Microthermometry reveals high Ca/Na ratios, suggesting that the brine composition evolved from hydrothermal alteration of the Variscan basement and partial dissolution and replacement of the host sedimentary rocks. δ37Cl values are lower than the expected value of evaporated seawater, suggesting Cl isotope fractionation by ion filtration in clay-rich horizons. Fluorite crystallized at minimum temperatures of 70 to 110 °C, 10–40 °C warmer than the host Triassic sedimentary rocks. Ascending brines were expelled during the Early Cretaceous and experienced a drop in pressure and temperature, together with possible mixing with the SO4-rich pore water of the sedimentary rocks, causing precipitation of silica, followed by fluorite and barite, forming a stratabound deposit similar to those found in many areas in Western Europe. [ABSTRACT FROM AUTHOR]

Carlin-type gold deposits are among the most important gold-bearing hydrothermal ore systems and are mainly located in Nevada, USA, and southwestern China. However, the source and evolution of the ore-forming fluids for these deposits remain controversial, especially those found within China. In this study, lithium and oxygen isotopic analyses of quartz-hosted fluid inclusions are used to elucidate the source and evolution of the giant Shuiyindong Carlin-type gold deposit. Fluid inclusions trapped in quartz of three distinct genetic stages have low salinity (0.8–6.3wt% NaCl equiv.) and moderate temperature (154–343 °C), but display variable Li and O isotope signatures. The Li and O isotopes of stage I fluids (δ7Li values from + 5.1 to + 9.1‰; δ18O values from + 6.3 to + 10.0‰) indicate predominantly a magmatic source for the initial ore-forming fluids. The large variations of Li and O isotopes of stage II fluids (δ7Li values from + 9.3 to + 16.0‰; δ18O values from + 0.1 to + 7.7‰) suggest that the fluids are controlled by mixing of magmatic fluids and meteoric water, which in turn triggered the precipitation of gold-bearing sulfides. The isotopic compositions of stage III fluids (δ7Li values from + 15.5 to + 22.8‰; δ18O values from − 5.4 to − 2.8‰) confirm that the final fluids are dominated by meteoric water. Furthermore, this work demonstrates that the combined Li–O isotopic analysis of fluid inclusions is a powerful tracer to decode the source and evolution of ore-forming fluids in hydrothermal mineralizing systems. [ABSTRACT FROM AUTHOR]

There is great exploration potential in Qiulitag Structural Belt, Kuqa Depression. In the Paleogene gypsum-salt phase transition zone, the reservoir sandstone thickness is thin and the process of hydrocarbon accumulation is complicated. In order to reveal the hydrocarbon charging stage and accumulation model, the fluid records about hydrocarbon in the intersalt thin sandstone of Kumugeliemu Group was studied by microscopic observation, Laser Raman spectroscopy, temperature measurement of inclusion, basin simulation, quantitative fluorescence spectroscopy of reservoir. The results show that: from the end of Paleogene to the Early Miocene, medium oil gathered on the top of Cretaceous sandstone; in the Middle Miocene, the charging of light oil-condensate occurred at 14.2 Ma, forming blue-green fluorescent inclusion assemblages and widely distributed paleo-oil reservoirs; between the Late Miocene and the Middle Pliocene, the ancient oil reservoirs were leaked by the development of thrust faults and structural fractures with the more intense tectonic compression; since the Late Pliocene, methane started charging at 3.7 Ma because of the recovering of gypsum-salt's sealing property with the deeper burial in Kumugeliemu Group, which is purer and thicker. The inclusions with methane and intersalt sandstone gas reservoir also formed at this period. The oil-gas accumulation model controlled by the dual control of gypsum-salt caprock and tectonic action. The result provides a reference case for further exploration in the middle-east section of Qiulitag Structural Belt. [ABSTRACT FROM AUTHOR]