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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 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.

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.

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 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).

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.

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.

Kalateh Pialeh prospect area is located in the Kopeh Dagh zone, approximately 15 km northeastern of Esfarayen city. The area is composed of sedimentary rocks deposited during the Jurassic, Cretaceous, and Tertiary periods, which include microconglomerate, dolomitic limestone, sandy limestone, limestone, conglomerate, and marl. Mineralization occurs as epigenetic deposits hosted by dolomitic limestone and limestone. Two mineralization stages were identified. The first stage consists of a pyrite-galena-sphalerite assemblage with replacement and breccia textures, and the second stage comprising a galena-sphalerite assemblage with vein-veinlet, open space filling, and replacement textures. Dolomite and calcite are the most abundant gangue minerals associated with lesser amount of quartz and barite. Main alterations consist of calcitization and dolomitization. Galena mineral exhibits maximum geochemical anomalies of 1843 ppm for zinc, 7 ppm for arsenic, and 11 ppm for copper. Microthermometric studies on primary fluid inclusions (LV) reveal homogenization temperatures ranging from 180°C to 265°C for stage 1, and from 167°C to 214°C for stage 2. Salinities for these stages were found to be between 7.8 wt.% to 14.5 wt.% NaCl equiv., and 11.7 wt.% to 12.2 wt.% NaCl equiv., respectively. Based on evidence such as structurally controlled mineralization, the type of alterations and their linear expansion, simple mineralogy of ore, geochemistry, and fluid inclusion data, Kalateh Pialeh prospect area is similar to lead-zinc epithermal deposits. Introduction Sediment-hosted Pb–Zn deposits are typically found in clastic-carbonate (Sedex type deposits) and carbonate (Irish type and Mississippi Valley-type (MVT) deposits) rocks (e.g., Goodfellow & Lydon, 2007). In Iran, the wide distribution of clastic and carbonate rocks has led to the formation of various types of sedimentary-hosted lead and zinc deposits.These deposits occur in Cretaceous carbonate units, including Malayer-Esfahan, Tabas- Poshte-Badam, Yazd-Anarak, and Central Alborz metallogenic belts (Rajabi et al., 2012). Kalateh Pialeh prospect area, located in Kopeh Dagh zone, about 15 km northeastern of Esfarayen city, is the first report of lead and zinc mineralization in this zone. Kopeh Dagh zone is characterized by the absence of magmatic activity, the presence of limestone formations, and abundant hydrocarbon reserves (such as Khangiran Gas Field). This study summarizes the alteration, mineralogy, geochemistry, and fluid inclusion studies, and then discuss the ore genesis of Kalateh Pialeh prospect area. Material and methods Following field work, thin sections and polished slabs from the host rocks, veins and veinlets were studied using optical microscope. Red alizarin was also used to differentiate between calcite and dolomite. Galena minerals were seperated from host rock by using standard techniques involving crushing and handpicking under a binocular microscope at Ferdowsi University of Mashhad. Minor and rare element metal concentrations from galena were analyzed using ICP-OES techniques on five samples at Zarazma laboratory in Iran, while XRD analysis of the samples was done at the same laboratory. Microthermometric analysis of fluid inclusions was carried out on seven samples using a Linkam THM 600 heating-freezing stage combined with an Olympus TH4–200 microscope stage at Ferdowsi University of Mashhad, Mashhad, Iran. Results and Discussion The area comprises sedimentary units of microconglomerate, dolomitic limestone, sandy limestone, limestone, conglomerate, and marl. Vein-type epigenetic mineralization occurs along fault zones with trending NW–SE/vertical dip in dolomitic limestone and limestone. Mineralization can be divided into two stages: Pyrite-galena-sphalerite assemblage (with replacement and breccia textures), and galena-sphalerite assemblage (with vein-veinlet, open space filling, and replacement textures). The main alterations consist of calcitization and dolomitization. The oxidation and weathering processes have resulted in the formation of hemimorphite, smithsonite, cerussite, goethite, and hematite in the ore zones. Gangue minerals consist of calcite and dolomite with lesser amounts of barite and quartz. Geochemical analyses of the galena mineral reveal maximum anomalies for zinc (1843 ppm), arsenic (7 ppm), and copper (11 ppm). Microthermometric studies on primary fluid inclusions (LV) show homogenization temperatures ranging from 180 to 265°C and from 167 to 214°C for stages 1 and 2, respectively. The fluid salinities for these stages range from 7.8 to 14.5 wt.% NaCl and from 11.7 to 12.2 wt.% NaCl, indicating a wide range of salinities.The temperature of ore-forming fluids in MVT deposits varies from 50 to 250°C, with the majority falling within the 70 to 170°C range , and their salinity is between 10 and 30 wt. % NaCl (Leach et al., 2010). In Kalateh Pialeh sam ples, primary fluid inclusions hosted in quartz crystals homogenize to the liquid phase at temperatures ranging from 167°C to 265°C, (mostly in the range of 80 to 200°C) and the average salinity of 11 wt. % NaCl. The salinity of the hydrothermal fluids at studied area varies from 7.8 to 14.5 wt. % NaCl. This wide range can be attributed to the mixing of two fluids with different salinities. These salinities can be divided into two groups with low salinity (7.8 to 10 wt. % NaCl) and high salinity (13.9 to 14.5 wt. % NaCl). The presence of two types of primary inclusions with different salinity but similar homogenization temperature is a sign of isothermal mixing of two fluids.

This study provides an in-depth analysis of fluid inclusions (FIs) and stable isotopes from the Manondo-Choma gold prospect in southern Malawi to understand the ore-forming mechanisms, genesis, and evolution of the hydrothermal fluids responsible for gold mineralization at the Manondo-Choma gold prospect. FIs and microthermometry studies were carried out on mineralized quartz veins from the area. The Manondo-Choma gold prospect is located in the southern Malawi within the Kirk range. Gold is mostly found in quartz veins within metamorphic rocks, such as gneiss and schists, and is structurally controlled by the NE–SW ductile shear zones. Gold mineralization is linked to quartz sulfide veins. Mineralization occurs in the following three stages: early, middle, and late, of which the middle stage is more plorific. The following three FI types were recognized in the quartz veins: pure carbonic, aqueous carbonic (CO2–H2O) and aqueous (H2O–NaCl) inclusions. Gold and associated mineralization were likely precipitated due to the lowering of pressure and fluid immiscibility. Oxygen isotope data indicate that the source of ore-forming fluids at the Manondo-Choma gold prospect was largely metamorphic in origin with minor magmatic input.

The Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Lintanchang area of the southeastern Sichuan Basin has good exploration and development conditions, and clarifying the paleo-fluid pressure evolution is of great significance for revealing the process of shale gas accumulation and fugitive emission. Taking the shale tectonic fractures and fluid overpressure fracture veins of the Wufeng-Longmaxi formations in Lintanchang area as the research object, the paleo-fluid pressure evolution process in this area and its controlling impact were investigated using cathodoluminescence, inclusion temperature measurement, laser Raman analysis, and basin simulation. The study shows that: (1) Lintanchang area has experienced four stages: normal pressure, mild overpressure to normal pressure, overpressure, and pressure relief. Overpressure is mainly due to hydrocarbon generation. Pressure relief is mainly caused by shale gas fugitive emission. The gas reservoir pressure relief reaches 54% of the initial pressure during the pressure relief stage. (2) There are two stages of vein filling in the fractures at the bottom of the black shale in the Wufeng-Longmaxi formations. The first stage is formed in the sedimentation and burial stage at 131-118 Ma, the temperature is 178-205 ℃, and the trapping pressure of methane inclusions is 105.6-119.8 MPa. The second stage is formed in the tectonic uplift stage at 25-18 Ma, the temperature is 150-175 ℃, the methane inclusions have relatively low salinity and its trapping pressure is 80.8-92.1 MPa. The low pressure coefficient (1.37-1.49) indicates that mass fugitive emission has occurred. (3) The late tectonic movement, especially the rapid uplift in the late Himalayan period, is the root cause of the fugitive emission and pressure relief of the gas reservoirs. The decrease of the roundness and pore size of the organic pores indicates the deterioration of reservoir physical properties. However, due to the long formation and preservation time of the gas reservoirs, the shale in the Wufeng-Longmaxi formations in Lintanchang area still has good exploration potential. This study is helpful to deepen the understanding of the accumulation mechanism of the normal-pressure shale gas reservoirs in Lintanchang area and can provide theoretical guidance for optimal selection of favorable shale gas exploration areas.

Tourmaline is a borosilicate mineral with general formula of XY3Z6[T6O18](BO3)3V3W. Experimental studies demonstrate a wide range of stability for tourmaline-supergroup minerals to record different geological processes. They occur in metamorphic, granitic pegmatites, and clastic sedimentary rocks and are associated with hydrothermal activities (Dutrow and Henry, 2011; Slack and Trumbull, 2011). Textural and compositional features of tourmaline can be used as an indicator of environment in which it crystallized. Tourmaline from porphyry deposits generally show a. frequently crystal zoning, b. development from Fe-rich to Mg-rich, and c. total Mg content is ~2 apfu in copper deposits and 1-2 apfu in Au deposits (Baksheev et al., 2012). It is believed that the world-class Dashkasan gold deposit records the transformation of porphyry to low-sulfide epithermal (Richards et al., 2006). The Dashkasan gold deposit located in the Kurdistan Province can be a significant region for better understanding the origin and the evolution of ore-forming fluids using chemistry of tourmaline. For the present study, we also tried to apply fluid inclusions data on quartz-tourmaline-pyrite veins from the Dashkasan deposit.Materials and MethodsPolished-thin sections of various tourmalines of the Dashkasan deposit were examined using a Cameca SX100 Electron Probe Micro Analysis (EPMA) at the Iran Mineral Processing Research Center, Karaj. Fluid inclusion studies were performed on quartz crystals of quartz-tourmaline-pyrite veins. The microthermometric parametes of fluid inclsions were measured by Linkam-THMS-600 stage at the University of Isfahan.Results and DiscussionThe Dashkasan gold deposit with 52 Mt of oxidized ore and average grades of 1.77 g/t Au is hosted by the Middle-Miocene porphyritic dacite/rhyodacite and dacitic breccia rocks. The main minerals are quartz, K-feldspar, hornblende and biotite mainly altered.. This deposit is characterized by the transition from the porphyry to the epidermal system with the presence of tourmaline minerals in phyllic and silicification alteration associated with gold veins. As petrographic examination shows tourmaline occurs as disseminated, vein/veinlet, and breccia textures in three types: Tur-1 occurred as needle shape in dacitic rocks associated with phyllic alteration; Tur-2 crystallized as radial shape mainly coexisting with silicification; and Tur-3 with elongated shape is present in dacitic breccia with phyllic alteration.Mineral ChemistryThe geochemical composition of three types tourmalines points to the nature and the evolution of ore-forming fluids. Electron microprobe analyses of the studied tourmalines indicate that the Tur-1 and Tur-3 are dravite, and the Tur-2 is dravite to schorl in composition and they belong to alkaline group. The third type, unlike the other two, is characterized by poor zoning and higher values of Na, K, Fe, Mg and lower values of Ca. On Fetot-Ca-Mg ternary diagram, they plotted in the Ca-poor metapelites, metapsammites, and quartz-tourmaline rocks host. Magmatic genesis inferred from the higher Fe/(Fe+Mg) ratio for Tur-1 and Tur-2, while this ratio in the Tur-3 is different and shifted towards hydrothermal source.Microthermometric StudyRichards et al. (2006) present the fluid inclusion assemblages from quartz-tourmaline veins in sericitized wall rocks in the Dashkasan deposit consisting of hypersaline and rare vapor-rich inclusion. They have homogenization temperatures of 246° to 360 ℃, yielding salinities of 34.4 to 46.1 wt% NaCl equiv. (Richards et al., 2006). Fluids inclusions studies on quartz-tourmaline-pyrite veins related to transition between stage-1 and stage-2 of mineralization in the Dashkasan shows a salinity values from 15.9 to 16.8 wt% NaCl equiv. and homogenization temperature values between 185° to 254 °C.ConclusionsOn the basis of optical and scanning electron microscopy, three tourmaline types(Turs -1,-2 and -3) in the Dashkasan deposit, can be distinguished. Despite the lack of zoning in Tur-1 and Tur-2, the third type displays the poor zoning. The first-and the third-types of tourmalines are dravite (Mg-rich), whereas the second-type is dravite to schorl in composition. Magmatic genesis is reflected by higher Ʃ(Fe+Mg) and FeO/(MgO+FeO) ratios for the first two types. While these ratios in the Tur-3 is different and shifted toward hydrothermal source. To sum up, the occurrence of quartz-tourmaline-pyrite veins in the Dashkasan deposit is due to the existence of a fault system under the physicochemical performance of the ore-mineralized fluid by a sudden depressurization and probably gradual mixing with shallow water.AcknowledgmentsWe thank Dr. Gholizadeh and Dr. Shabanian for their assistance with experiments for EPMA. This study was financially supported by the University of Isfahan.

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 δ34S values ranging from −0.7 to 4.2 (mean: 1.8 ± 1.5, 1σ), 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. Th: 222.9; salinity: 6.74 wt.% NaCl eqv.), Type-2 (avg. Th: 185.72; salinity: 16.56 wt.% NaCl eqv.), and Type-3 (avg. Th: 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.

In this paper, through the Raman spectroscopy analysis of fluid inclusions in Lala copper deposit, it is found that the types of fluid inclusions are diverse, including not only single pure gas phase or pure liquid phase, gas-rich phase, liquid-rich phase, and many daughter crystals, but also melt-fluid inclusions. The gas phase components of fluid inclusions are not limited to the CO2, but also include N2, CH4 or a mixture of the three. Not only halide daughter crystals but also calcite and hematite daughter crystals are found in fluid inclusion daughter minerals. In conclusion, the Raman spectroscopy characteristics of fluid inclusions show that the ore-forming fluids of the Lala copper deposit have the characteristics of multiple stages and complex sources.

The Saxi tungsten-beryllium deposit is located in the Laojunshan tungsten-tin polymetallic metallogenic area in southeastern Yunnan. Determining the fluid nature, source, and evolution process of early layered orebodies and late vein-like orebodies and constraining their fluid geochemistry and isotopes can effectively explore the metallogenic mechanism of the Saxi tungsten-beryllium deposit, which is a collection of Laojunshan deposits. This study provides theoretical thinking for future prospecting work in the district. The formation of vein-like ore bodies in this deposit experienced a silicate stage, an oxide-sulfide stage, and a carbonate-fluorite stage. Scheelite and beryl were mainly formed in the first two stages. This article studies the fluid inclusions in quartz at different stages of the orebodies of the Saxi tungsten-beryllium deposit, including petrographic characteristics, microscopic temperature measurements, and laser Raman spectroscopy. The quartz sample's hydrogen-oxygen isotope composition in the ore-like ore body was tested. Three primary types of fluid inclusions (FIs) in vein-like ore bodies are detected, i.e.: liquid-rich FIs, gas-rich FIs, and aughter minerals bearing FIs. The gas phase composition of FIs is mainly H2O, with a small amount of reducing gas such as C2H2, and the liquid phase composition is also mainly H2O. From the silicate stage to the carbonate-fluorite stage, the peak homogenization temperature and salinity (NaCleq) of FIs are 240-360℃, 2.35%-13.81%; 220-310℃, 4.03%-9.86%, and 190-270℃, 2.41%-6.88%. From early to late, both homogenization temperature and salinity of the ore-forming fluid decreased obviously. The ore-forming fluid is generally a medium temperature, low salinity, CO2-poor NaCl-H2O fluid system. The δD and δ18O values of the quartz samples from early quasi-layered ore body are -102.8‰ to -99.0‰ and 11.7‰-13.0‰ respectively, and the corresponding δ18O value of the H2O value is 3.16‰-6.46‰. The δD and δ18O values of the quartz samplesfrom bulk oxide-sulfide section are -99.6‰ to -69.5‰ and 11.2‰-14.1‰ resoectively, and the corresponding δ18O value of H2O value is 3.08‰-6.73‰. This indicates that the ore-forming fluid mainly sourced from magmatic water mixed with a small amount of atmospheric precipitation or organic water.The fluid may boil, forming the precipitation of the main ore-forming minerals in the late vein-like ore body oxide-sulfide stage. The Saxi tungsten-beryllium deposit belong to a medium-to high-temperature hydrothermal system.

High-purity quartz, famous for low impurities and high purity, has been widely used in optical fiber communication, photovoltaic, aerospace, semiconductor display and other high-tech industries. Fluid inclusions, either derived from primary ore-forming fluids or captured by quartz in late geological actions, are typical fluid impurities in crystal quartz. In particular, some small gas and liquid inclusions encapsulated in quartz crystals are difficult to be separated effectively by conventional mineral processing techniques. In this paper, the basic characteristics of fluid inclusions in high purity quartz are described in detail, and the current status of fluid inclusions activation and separation technology is summarized. Based on the research progress of the basic theory of high-purity quartz in China in recent years, some scientific suggestions on the basic theory of high-purity quartz in China are put forward.

No breakthrough has been made in petroleum exploration of the Sinian Dengying Formation in the southeastern Sichuan Basin as the major factors controlling the hydrocarbon accumulation of the Dengying Formation have not been well established, including the development period and distribution of the platform margin, the effectiveness of the source-reservoir combination and the reliability of the Cambrian pre-salt structural trap. Based on the interpretation of seismic data and hydrocarbon-source correlation, the distribution of the platform margin of the Sinian Dengying Formation in the southeastern Sichuan Basin was mapped. Moreover, the gas source rocks of the Dengying Formation were clarified according to geochemical characteristics of fluid inclusions, and the pre-salt structures were further confirmed by seismic forward modeling and experiments of prestack depth migration. Results showed that the sedimentary facies of the 4th member of Dengying Formation in the southeastern Sichuan Basin was platform margin of gentle slope type. The platform margin reservoir of the Dengying Formation and the Lower Cambrian source rocks constitute a favorable source - reservoir combination. The carbon isotope characteristics of gas in fluid inclusions indicate that some of the oil/gas in the Dengying Formation were contributed by the Doushantuo Formation source rocks. As the difference in seismic velocities between carbonate rocks and gypsum/salt beds may cause a reduction in the amplitude of pre-salt structures, the low-amplitude structures identified on current seismic profiles are underestimated instead of overestimated. Accordingly, the Sinian structural traps are confirmed to develop in the deep pre-salt sequences in the low-steep anticline belt, southeastern Sichuan Basin. On the basis of the above new understanding, we propose two types of hydrocarbon migration modes for the Sinian Dengying Formation in southeastern Sichuan Basin, including lateral migration of hydrocarbons generated from the Cambrian Qiongzusi Formation and vertical migration of hydrocarbons derived from the Sinian Doushantuo Formation. Lithologic traps at the platform margin and pre-salt structural traps within the platform are favorable targets for natural gas exploration.

There are a large number of natural gas shows in the Upper Paleozoic of the central Hunan Basin. However, the hydrocarbon accumulation process was complicated due to the strong tectonic reformation in this area. A study of the natural gas accumulation period is of significance for determining gas accumulation models. In this research, the fluid inclusion samples were tested, the fluid inclusion occurrence characteristics, uniform temperature data, and reservoir evolution were analyzed, and four diagenetic periods and four diagenetic periods and three hydrocarbon accumulation periods were identified. (i) For the syntaxial stage, the filling is dark and nonluminous, and the fluid captured by the overgrowing cement around the particles is mainly seawater; (ii) for the (Early) Mesogenetic burial stage, the calcite cement grows around the particles or micritic calcite matrix, and the fluid captured is mainly brine; (iii) for (Late) Mesogenetic burial stage, two sets of decomposed fissures developed in massive calcite colloids with non-luminous gas-rich hydrocarbon inclusions within the crystals; and (iv) for Telogenetic burial stage, weakly fluorescent pure gaseous hydrocarbon inclusions are developed in luminescent calcite veins. The result indicates that the organic inclusions in the Lower Carboniferous of the central Hunan Basin are dominated by weakly fluorescent and nonfluorescent rich gas inclusions and pure gas-phase inclusions, with three stages of hydrocarbon filling. By integrating the average homogenization temperatures on burial curves, the three charging orders correspond to 260–250 Ma during the Late Permian, 249–245 Ma during the Early Triassic, and 208–170 Ma during the Late Triassic. Dense reservoir characteristics reveal deep basin gas reservoir in deep basin.

The Haxi gold deposit located in the Hatu–Saertuohai metallogenic belt of the west Junggar region, China, is a newly discovered gold deposit with proven reserves of ∼10 tons of gold and an average grade of 6.70 g/t. Primarily, the deposit is hosted in the early Carboniferous Tailegula Formation, controlled by the NEE-trending Anqi fault. The gold ore bodies contain gold-bearing quartz veins and altered basalt. The ore mineral is dominated by abundant sulfides, such as pyrite, arsenopyrite, chalcopyrite, and a little gersdorffite. To date, three types of fluid inclusion in quartz veins have been identified: liquid–gas (V-type), CO2–H2O (C-type), and liquid–rich (L-type). The ore-forming fluids exhibit medium homogenization temperatures (Th) of 226 °C–325 °C with low salinities of 2.24–9.34 wt% NaCl equivalent and low densities from 0.72 to 0.88 g/cm3. The δD values range from −115.3‰ to −100.7‰, with an average value of −109.1‰; the δ18O values range from 11.3‰ to 12.2‰, with an average value of 11.8‰; and the δ34S values in sulfide range from 0.3‰ to 1.8‰, with an average of 1.2‰. The average values of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in sulfide are 18.059, 15.547, and 37.996, respectively. To summarize, the metallogenic fluids were derived not from a single source but from late magmatic–hydrothermal fluid mixed with paleo-atmospheric water; furthermore, the ore-forming materials principally originated from a crust–mantle mixed source. The Pb model age calculated using Hautman’s formula is 347–365 Ma, leading to the speculation that the metallogenic period may be Devonian–Carboniferous.

Introduction Varmazyar Pb–Zn (Ag) occurrence, 65 km north of Zanjan, is located in the Tarom–Hashtjin metallogenic belt (THMB). The THMB has been recognized as one of the most important epithermal metallogenic belts in Iran (Kouhestani et al., 2018b) that host numerous small- to medium-sized epithermal deposits (i.e., Gulojeh, Aqkand, Aliabad–Khanchy, Chodarchay, Khalyfehlou, Chargar, Zajkan, Marshoun, Abbasabad, Zehabad, and Shah Ali Beiglou). These epithermal deposits are temporally and spatially related to late Eocene granitoids (Mehrabi et al., 2016; Kouhestani et al., 2018b). Although the general geological characteristics of the region, where the Varmazyar occurrence is located, were determined (Faridi and Anvari, 2000), no detailed studies have been conducted on the mineralogy, geochemistry, and the ore-forming fluids characteristics of the Varmazyar occurrence. In this paper, we investigate the geology, mineralogy, geochemistry, fluid inclusions, and alteration styles of the Varmazyar occurrence to constrain its ore genesis. These results may have implication for the regional exploration of epithermal deposits in the THMB. Materials and methods Detailed field work has been carried out at different scales in the Varmazyar area. A total of 70 samples were collected from various parts of ore veins and breccias, host tuff units and granitoid intrusion. The samples prepared for thin (n=15) and polished-thin (n=27) sections in the laboratory of University of Zanjan, Zanjan, Iran. Representative 7 samples from the mineralized veins and breccias, 1 sample from host intermediate tuff unit and 1 sample from barren and fresh granite intrusion, were analyzed for rare and rare earth elements using ICP–MS in the Zarazma Analytical Laboratories, Tehran, Iran. Fluid inclusion measurements have been conducted on 4 doubly polished thick (~150 μm) sections including crystalline quartz, and sphalerite from the second, and third stages of ore formation. Microthermometric measurements were performed using a Linkam THMSG-600 heating–freezing stage attached to a ZEISS microscope in the fluid inclusion laboratory of Iranian Mineral Processing Research Center, Tehran, Iran. Results and Discussion The geological units hosting the Varmazyar occurrence are mainly Eocene volcanic and volcaniclastic rocks that were intruded by late Eocene granitoids. The volcaniclastic rocks can be divided into two units as acidic (lithic tuff, lithic crystal tuff and crystal tuff) and intermediate (lithic crystal tuff, crystal tuff, and lithic tuff) units. They are metamorphosed to clinopyroxene hornfels facies near contact intrusions. The granodiorite intrusion is the main rock units in the Varmazyar area. It crops out mainly in the south, southwest and northeast of the Varmazyar occurrence. It ranges in composition from monzogranite to syenogranite and shows porphyritic and granular textures. Mineralization at Varmazyar occurs as epithermal base metal quartz-sulfide brecciated vein that occupy NS-trending faults in the Eocene acidic and intermediate tuff units. The ore vein extends up to 300 m along, from several cm to 2–3 m wide, and generally dip steeply (65–80°) to the west. Wall-rock alterations developed at the Varmazyar occurrence include silicification, intermediate argillic, carbonate, and propylitic alteration; the first three are closely related to the Pb–Zn (Ag) mineralization. The alteration styles show a systematic zonation pattern, from the silica, via intermediate argillic, to propylitic alteration. Four stages of mineralization can be distinguished at Varmazyar. Stage 1 is represented by silicification of host rocks along with minor disseminated pyrite. This stage is a pre-ore stage and usually crosscut by later stages. Stage 2 is the main ore-stage at the Varmazyar occurrence. It is characterized by up to 5 cm wide quartz veins and breccias that contain variable amounts of disseminated galena, sphalerite, and minor pyrite. Clasts of this stage and associated wall-rock alteration have been recognized in the hydrothermal cements of stage 3 breccias. Stage 3 is marked by quartz-calcite-manganese oxides (psilomelane, pyrolusite, braunite) veins and breccia cements. It is usually crosscut previous mineralization stages and, in turn, is cut by stage 4 calcite veinlets. Stage 4 is a barren post-ore stage represented by < 1 mm wide calcite veinlets. This stage usually crosscuts previous ore stages. No sulfide minerals are recognized with stage 4. The ore minerals at Varmazyar formed as vein-veinlet and hydrothermal breccia cements, and show disseminated, vein-veinlet, brecciated, comb, crustiform, colloform, cockade, bladed, plumose, and vug infill textures. Galena, sphalerite, pyrite, psilomelane, and pyrolusite are the main ore minerals; smithsonite, cerussite, goethite, secondary pyrolusite, and braunite are supergene minerals. Quartz, calcite, and sericite are present in the gangue minerals. Comparison of Chondrite–normalized rare elements and REE patterns of host intermediate tuffs, barren and fresh granite intrusion, and the mineralized samples at Varmazyar indicate that mineralization is probably genetically related with granite intrusions. In this case, leaching of some elements from the host tuff units may have involved in mineralization. Ore-forming fluids associated with the quartz-sulfide veins are represented by two-phase aqueous inclusions and by H2O–NaCl fluids with moderate-temperature (135–249 °C) and low-salinity (0.2–6.4 wt.% NaCl equiv.). Fluid inclusion data indicates that fluid boiling and mixing were important processes in the evolution of the ore-forming fluids at Varmazyar. Our data suggest that Varmazyar is an example of intermediate-sulfidation type of epithermal base metal mineralization.

A giant fault-controlled oilfield has been found in the ultra-deep (greater than 6000 m) Ordovician carbonate strata in the northern Tarim Basin. It is of great significance for hydrocarbon accumulation study and oil exploitation to determine the key oil accumulation periods. Based on detailed petrographic analysis, fluid inclusion association (FIA) in calcite samples filling in fractures from 12 wells were analyzed, and key accumulation periods of the strike-slip fault-controlled oilfield was studied by combining oil generation periods of the source rocks, formation periods of the fault and traps, and the fluid inclusion data. (1) There are multiple types of FIA, among them, two types of oil inclusions, the type with yellow fluorescence from the depression area and the type with yellow-green fluorescence from the uplift area with different maturities indicate two oil charging stages. (2) The homogenization temperature of the brine inclusions in FIA is mostly affected by temperature rises, and the minimum temperature of brine inclusions symbiotic with oil inclusions is closer to the reservoir temperature during its forming period. (3) FIA with yellow fluorescence all have homogenization temperatures below 50 °C, while the FIA with yellow-green fluorescence have homogenization temperatures of 70–90 °C tested, suggesting two oil accumulation stages in Middle–Late Caledonian and Late Hercynian. (4) The Middle–Late Ordovician is the key formation period of the strike-slip fault, fracture-cave reservoir and trap there. (5) The oil generation peak of the main source rock of the Lower Cambrian is in the Late Ordovician, and the oil accumulation stage is mainly the Late Ordovician in the depression area, but is mainly the Early Permian in the uplift area. The key oil accumulation period of the strike-slip fault-controlled reservoirs is the Late Caledonian, the depression area has preserved the primary oil reservoirs formed in the Caledonian, while the uplift area has secondary oil reservoirs adjusted from the depression area during the Late Hercynian. Oil reservoir preservation conditions are the key factor for oil enrichment in the strike-slip fault zone of northern Tarim, and the Aman transition zone in the depression is richer in oil and gas and has greater potential for exploration and development.

Based on a combined in-situ calcite U-Pb dating, molecular geochemical correlations of reservoir oil and extract from reservoir rocks, and fluid inclusion analysis, the charge and evolution history of the YJ1X ultra-deep oil reservoir of the Ordovician Yijianfang Formation in the southwestern part of the Tabei Uplift has been determined systematically. (1) The reservoir oil, free oil and inclusion oil have similar geochemical characteristics and are presumably derived from marine source rock deposited in similar sedimentary environment. (2) The reservoir oil, free oil and inclusion oil have similar maturities with calculated equivalent vitrinite reflectance values in the range of 0.80%–0.96%. (3) Two types (Group I and II) of oil inclusion assemblages (OIAs) have been identified in the reservoir, of which Group I represents the original gas-saturated oil entering the trap during the initial oil charge, whereas Group II represents undersaturated residual oil retained in the reservoir after minor leakage of light hydrocarbon. (4) The reservoir experienced oil charge only once during the Early Devonian around 425 Ma and has been well preserved after the minor light hydrocarbon leakage in the Middle Devonian. The study shows that there may be old oil and gas accumulations in ultra-deep strata of petroliferous basins with well-developed caprock and stable tectonic background.

The Dawangzhuang buried hill zone is a typical representative of Paleozoic oil and gas exploration in the Jiyang Depression, Bohai Bay Basin, and has experienced a complicated accumulation process. Using petrographic observation, microthermometry and abundance of hydrocarbon inclusions, the Paleozoic hydrocarbon charging process in Dawangzhuang buried hill zone was discussed. The study shows that the Paleozoic reservoirs developed hydrocarbon inclusions in the study area. Ordovician hydrocarbon inclusions with pale yellow and blue-green fluorescence distributed along the calcite veins and particle healing joints. Asphalt inclusions and oleaginous are only distributed in Dagu 671 oil reservoir with a small scale. The main peaks of the homogenization temperature are from 80 ℃ to 90 ℃ and from 100 ℃ to 110 ℃; Carboniferous-Permian hydrocarbon inclusions with blue-green fluorescent distributed along the micro-cracks of quartz particles and secondary enlarged edges. The main peak of the homogenization temperature is from 100 ℃ to 110 ℃. Combining with the hydrocarbon generation and expulsion periods of source rocks, it can be concluded that there are two stages of hydrocarbon charging in the Paleozoic in the study area. The first stage of oil and gas charging occurred in the late Dongying period (27~25 Ma), which was a small-scale accumulation of Paleozoic, mainly in the Ordovician; the second stage of oil and gas charging occurred from the end of Guantao period to the end of Minghuazhen period (5~2 Ma), which was a large-scale accumulation of Ordovician and Carboniferous-Permian. The development of asphalt inclusions near the Dagu 671 well area and the fact shown by the Effective Grids containing Oil Inclusions (EGOI) that the ancient oil-water interface is lower than the current one are related to the activity of the Da 1 fault at the end of the Minghuazhen period (2 Ma), resulting in local adjustments and smaller scope of oil and gas reservoir.

The Wunugetushan large porphyry Cu–Mo deposit in NE China is hosted by Mesozoic quartz monzonite porphyry and has a Mo-rich core and Cu-rich rim in space. In this paper, melt inclusions in porphyry intrusions and fluid inclusions in different-stage quartz veins were studied to explore potential parameters leading to Cu–Mo decoupling. Melt inclusions in porphyry intrusions have rhyolitic compositions of 71.7–85.3 wt.% SiO2, 1.9–31.3 ppm Cu and 1.7–2.6 ppm Mo. Hydrothermal activity occurred over three stages: 1) Early Mo mineralization at high temperatures (543°C–560°C) and CO2-rich fluids of intermediate salinity (11.0–17.3 wt.% NaCl equivalent), accompanied by biotitization and minor K-feldspathization; 2) Late Mo mineralization involving high-salinity (up to 77.0 wt.% NaCl equiv.) oxidized fluids at intermediate temperatures (400°C–454°C), with K-feldspathization and minor sericitization; 3) A Cu-mineralization stage with high-salinity (up to 45.6 wt.% NaCl equiv.) and CO2-barren fluids characterized by temperature peaks at 250°C–300°C and 400°C–450°C, accompanied by sericitization and illitization. Given possible variations in melt Cu/Mo ratios during magmatic activity and redox conditions, pH, fluid composition, and temperature during the hydrothermal-fluid stage led to the separation of Cu and Mo, we found that integrated parameters including increased Cu/Mo ratios in residual melt, variations in the redox state and more acidic environment of hydrothermal fluids determine spatial separation of two metals.

Inorganic and organic fluids are widely found in sedimentary basins during oil and gas migration and accumulation. This research investigates two types of sandstone reservoirs with different pressure states and fluid evolution of the Shahejie Formation in the western slope belt of Dongpu Sag. Based on petrographic observations, micro-Raman spectroscopy, and fluorescent spectrometry, petroleum inclusions, CH4-bearing inclusions, and CO2-bearing inclusions were discovered in quartz-hosted minerals. The pressure–temperature–time–composition (P–T–t–X) properties of the CH4 and CO2 inclusions were obtained by quantitative Raman analysis and thermodynamic models. Minimum trapped pressure was predicted by the thermodynamic modeling of petroleum inclusions. Saffron yellow petroleum inclusions represent an early Oligocene oil-charging event (∼32–30 Ma), and the two kinds of reservoirs were all kept in moderate-overpressure conditions (average pressure coefficient: 1.26). Due to rapid uplift and denudation (Dongying movement) in the middle Oligocene in step II, crude oil degrades into CH4 and CO2 (density of CH4 gas inclusions: 0.1010–0.1339 g/cm3; density of CO2 gas inclusions: 0.450–0.612 g/cm3) and retains low-maturity (0.67–1.04%) bitumen in situ. Tectonic destruction causes the reservoir to be released to normal pressure. With the reburial of the Es3 Formation, step II entered the middle stage of oil generation again (average pressure coefficient: 0.90). However, in step I, with secondary hydrocarbons occurring, second-stage oil (performance for pale blue fluorescence in petroleum inclusions) accumulated at ∼12–0 Ma (late Miocene–Pliocene). The second oil charging event in step I remains a reservoir under high-overpressure conditions (average pressure coefficient: 1.67).

The Shibaogou deposit is located in the Luanchuan ore district within the East Qinling orogenic belt (EQOB), central China, which is a newly discovered Mo–Pb–Zn skarn deposit. The skarn and Mo–Pb–Zn ore bodies are mostly hosted in the contact zones between the Shibaogou porphyritic granite and carbonaceous sedimentary rocks from the Luanchuan and Guandaokou sets. A study combined of geochronology, fluid inclusion (FI), and stable isotopes was performed to constrain the mineralization age, source of ore materials, and the origin and evolution of the ore-forming fluids and their relationship with the subduction of the Paleo-Pacific Plate. The mineralization process includes skarn and quartz–sulfide episodes, which has four stages: skarn (I), quartz–molybdenite (II), quartz–galena–sphalerite (III), and quartz–calcite (IV). Molybdenite Re-Os dating suggests that the deposit was formed in the Late Jurassic (147.4 ± 7.2 Ma). Reportedly, there are five primary types of fluid inclusions: L-type, V-type, H-type, S-type, and C-type. In the skarn stage, coexisting H-type (35.58 wt%–46.05 wt% NaCl equiv.) and low-salinity V-type (0.35 wt%–5.7 wt% NaCl equiv.) fluid inclusions show similar homogenization temperatures, which suggests that fluid boiling occurred at 513–550°C and 580–650 bar (2.19–2.45 km). In the quartz–molybdenite stage, the homogenization temperatures of L-type, V-type, minor H-type, and S-type fluid inclusions indicate continued fluid boiling at 324–387°C and 180–250 bar (0.49–0.94 km). In the quartz–galena–sphalerite stage, a fewer number of coexisting V-type and L-type fluid inclusions in quartz shows different salinities with similar homogenization temperatures, indicating that they are trapped at 303–347°C and

In this study, petrographic, microthermometric, and synchrotron radiation X-ray fluorescence (SRXRF) analyses of fluid inclusions were conducted to shed light on the mineralization mechanism of the Dongtongyu deposit and provide some evidence of the relationship among CO2, Au, and other ore elements (e.g., Cu, Fe, Zn, and Pb) in ore-forming fluids. The ore-forming fluid is characterized as the H2O–CO2–NaCl system with medium–high temperatures and low salinities. Four structural mineralization stages are distinguished: Pyrite-quartz (Stage 1), gold-quartz-pyrite (Stage 2), gold-quartz-polymetallic sulfide (Stage 3), and quartz-calcite (Stage 4). Fluid inclusions in Stages 1–3 are dominated by the H2O–CO2 type, and most of them contain liquid H2O and liquid CO2 at room temperature. The melting temperatures (Tm-CO2 = −82.1°C to −57.5°C) of solid CO2 in Stage 1 are relatively low. The values of Tm-CO2 in Stages 2–3 are quite close, with ranges of −60.5°C to −56.5°C and −59.2°C to −58.6°C, respectively. The melting temperatures of clathrate in Stages 1–3 are −2.7°C to +7.8°C, −5.5°C to +7.8°C, and +3.7°C to +7.2°C. The homogenization temperatures of the CO2 phase in the H2O–CO2 inclusions of the three stages are measured as −7.5°C to +31.7°C, −7.5°C to +29.3°C, and 7.1°C to +24.1°C. The total homogenization temperatures in Stages 1–3 are 180°C–394°C, 202°C–305°C, and 224°C–271°C, with salinities of 4.3 wt.%–18.2 wt% NaCl, 4.3 wt.%–20.0 wt% NaCl, and 5.3 wt.%–11.0 wt% NaCl, respectively. The laser Raman spectroscopy results show that the CO2–H2O inclusions in the quartz veins contain abundant CO2 and CH4. The SRXFR results show that most of the elements, especially As, Te, and Cu, are more enriched in liquid CO2 than in liquid H2O. The elements of Au, Fe, Ni, Cu, and Pb have higher concentrations in H2O–CO2-type fluid inclusions in Stage 2 than other fluid inclusions in Stages 1–2, suggesting that gold mineralization is closely related to CO2-rich fluids. During the fluid evolution process, fluid immiscibility is an important mineralization mechanism of gold. The increase in CO2 and CH4 and the decrease in the fluid temperature might promote fluid immiscibility.

Introduction The widespread Cenozoic magmatic assemblages in Iran host a variety of ore deposits including porphyry Cu-Mo-Au, skarn type ores, and epithermal base and precious metals deposits. Silicic zones of variable sizes are common in the Kerman belt in the southern section of the Urumieh-Dokhtar arc, and some might be representing the upper parts of porphyry copper systems known as lithocap. To investigate this potential relation, a silicic zone in Meideh, north Pariz, is studied. The silicic zone lies in an area with several known porphyry copper deposits (PCD) including Sarcheshmeh, Nochun, Seridun, Sarkooh, and Bagh-Khoshk. For comparison, silica ledges and veins in Seridun and a mineralized silica vein system to the east of the Sarcheshmeh mine are also studied. Materials and methods The study is based on field studies and investigation of textures and structures, and sampling for mineralogy (microscopic and X-ray diffraction analysis), and fluid inclusions. The XRD analyses were accomplished in the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and Kansaran Binaloud Co, Tehran. The fluid inclusion studies were performed in the Iranian Mineral Processing Research Center (IMPRC) using a Linkam THMS600 equipped with a Zeiss microscope. Results The silicic zone in Meideh is developed in andesitic lava flows and pyroclastic materials, and covers an area of ~ 1 km2. Silica occurs in white to grey colors and in massive, brecciated and locally vuggy textures; the grain sizes range between 0.01mm to 1mm. The silica is locally associated by minor sulfides (pyrite and locally chalcopyrite) carbonates, and clay minerals. The silicic zone grades outward into a silicic-argillic halo and into the host volcanic rocks with propylitic alteration. Chemical analysis of samples from the zone indicated enrichments in Cu, Mo, Ag, As, Bi and Au relative to the average composition of intermediate-mafic volcanic rocks in the Kerman belt. Small outcrops of a quartz-tourmaline rock occur in the southeast of the silicic zone. In Seridun, silica ledges and veins occur in the periphery and in the upper parts of a porphyry copper deposit developed in Miocene shallow intrusive bodies and older volcanic rocks. In east of Sarcheshmeh, several N-S striking silica veins locally containing pyrite, chalcopyrite, malachite, and Fe-oxides/hydroxides occur in Cenozoic volcanic and intrusive host rocks. In both areas, the silicic zones are products of pervasive silicic alteration, and occur in massive, breccia, and vuggy textures. Vuggy texture is well developed in Seridun. XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from all three areas are dominated by two-phase liquid-vapor. Homogenization temperature (TH) varies between 140-263 oC (average: 202 oC) for Meideh, 195-320 oC (average: 247 oC) for Seridun, and 140-264 oC (average: 177 oC) for east of Sarcheshmeh. Salinities vary between 0.18-5.71 (average: 1.62), 1.22-4.18 (average: 2.27), and 0.7-3.39 (average: 1.57) wt.% NaCl eq., respectively. The quartz-tourmaline rock from Meideh is distinguished by the occurrence of liquid-vapor-halite±hematite and liquid-vapor-opaque inclusions, in addition to liquid-vapor inclusions. The TH and salinity for the liquid-vapor inclusions, homogenizing to liquid, varies, respectively, between 202-269 oC (average: 231 oC) and 3.71-7.16 (average: 5.43) wt.% NaCl eq. The TH and salinity for the halite bearing inclusions, homogenized by halite dissolution, varies between 240-480 oC (average: 345 oC) and 33.40-56.90 (average: 42.80) wt.% NaCl eq. Discussion The textures, structure, and spatial relations with the host volcanic rocks suggest that the Meideh silicic zone developed as a result of pervasive silicic alteration, rather than open space filling. Textures indicative of open space filling, including crustification and symmetric banding, are absent in Meideh. The silicic ledges in Seridun, and the N-S striking silicic zones in east of Sarcheshmeh, are the products of pervasive silicic alteration of the host volcanic and intrusive rocks. The XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from the three silicic zones are dominated by two-phase liquid-dominant L-V inclusions. No distinction in salinity can be made between the three zones; Seridun, however, is distinguished by higher homogenization temperature. The local quartz-tourmaline zones in Meideh developed from distinctly higher temperature and salinity fluids (240-480 oC and 33.9-64 wt.% NaCl eq., respectively). A comparison of fluid inclusion data with several epithermal base and precious metals systems in the Urumieh-Dokhtar arc and elsewhere in Iran suggest that no meaningful distinction can be made between barren (i.e. Meideh, at current exposure level) and productive epithermal systems. Our data indicate that the silicic zone in Meideh cannot be considered as a porphyry-related lithocap at current exposure. The quartz-tourmaline rock developed from fluids of higher salinity and temperature suggests a link with magmatic-hydrothermal systems and warrants further investigation. Acknowledgements We would like to thank Mr. Afrouz for introducing the area, help with field works, and discussions. We are grateful to Mr. Imani from Parsolang for his help with field works and discussions, and to Ms. Aghajani from Iranian Mineral Processing Research Center for her invaluable help with the fluid inclusion studies. Dr. Ashrafpour kindly provided us with geological maps and chemical analysis of samples from the Meideh silicic zone. The study was supported by the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and a Shahid Beheshti University grant to S.A.

The Kaymaz gold deposit comprises Damdamca, Karakaya, Küçük Mermerlik, and Kızılağıl ore zones within an area underlain by serpentinite and far-traveled Paleozoic-Mesozoic high-pressure metamorphic rocks. The Kızılağıl ore zone is hosted in silicified quartz schist, whereas the others are hosted in silica altered serpentinite. Pyrite-I, arsenopyrite, marcasite, magnetite, pentlandite, millerite, nickeline, bravoite, and fine-grained native gold and silver comprise the first stage, whereas pyrite-II and chalcopyrite represent the second ore stage. The Kaymaz gold deposit has been defined as a silica-listwaenite hosted gold deposit according to host rock relations and mineralogical properties.Gold, Ag, and As were found to be highly correlative in whole-rock silica-listwaenite analyses. Higher As content of the pyrite-I, coexisting native gold and silver together with the whole-rock analyses indicate that these metals were derived from the same source, possibly the Kaymaz granite. On the other hand, clathrate formations observed in some of the first stage fluid inclusions confirm that high Ni in the pyrite-I may have been derived from the serpentinites. However, a distinct lack of the separated carbonic phase and clathrate formations in the second stage fluid inclusions as well as their lower Th and salinities, reveal that higher Co in the pyrite-II possibly dissolved from the metabasites by meteoric solutions.

Introduction The Gharehkand area is located in the southeast of Maragheh city and in Takab metallogenic district. According to the structural divisions of Iran, this area is situated south of the volcanic Mount Sahand in the Central Iran zone (Stocklin, 1968). This paper aims to investigate the characteristics of gold-bearing vein-veinlets and physicochemical conditions of ore-forming fluids in the Gharehkand area. Materials and methods About 40 rock samples were collected from mineralized zones and host rocks. The thin and thin-polished sample sections were studied in the geology department of the Mohaghegh Ardebili University, Ardebil. Microthermometric data were obtained from fluid inclusions using the Linkam THMS600 stage at the Payame Noor University of Tabriz. Results 1) The mineralization in the Gharehkand area took place principally as vein-veinlets within the host sedimentary rocks during two main stages. Mineralization occurred in quartz vein-veinlets during the first stage. The quartz crystals within the quartz vein-veinlets display brecciated, boxwork, drusy, and comb textures. During the second stage barite mineralization occurred as vein-veinlets. The mineralization of sulfides (galena, sphalerite, pyrite, and chalcopyrite) and gold occurred within the quartz vein-veinlets of the first stage. 2) The values of homogenization temperature (Th) and salinity of fluid inclusions vary from 80°C to 220ºC and 6 to 13 wt.% NaCl eq., respectively. 3) The study of fluid inclusions demonstrated that boiling and simple cooling were the most important mechanisms in the ore deposition at Gharehkand, and the sulfide complexing ligands played an effective role in transporting metals within the ore-forming hydrothermal fluids. 4) The quartz crystals textures (brecciated, boxwork, and comb) in quartz vein-veinlets and microthermometric data (low salinity and Th) of the ore-forming fluids indicate that mineralization at Gharehkand is of epithermal type with low-sulfidation style. Discussion The mineralization in the Gharehkand area took place principally as vein-veinlets within the host sedimentary rocks. Two main stages of mineralization were distinguished at the Gharehkand area. Stage-1 mineralization is represented by the quartz vein-veinlets. The quartz crystals within the quartz vein-veinlets display brecciated, boxwork, drusy, and comb textures. The formation of quartz crystals in quartz veinlets and micro-veinlets were temporally divided into three sub-stages: early, middle, and late. Stage-2 mineralization is represented by barite vein-veinlets. The hypogene alteration is mainly observed as the development of silicic halos around quartz vein-veinlets within the host sedimentary rocks. The mineralization of sulfides (galena, sphalerite, pyrite, and chalcopyrite) and gold have occurred within the late sub-stage quartz veinlets and micro-veinlets. Oxidized processes have caused formation of goethite, hematite, jarosite, malachite, and azurite. Copper sulfides (covellite, chalcocite, and digenite) are formed in the supergene zone. Based upon phase content, the studied fluid inclusions in late sub-stage quartz crystals may be classified into three types: liquid-rich two-phase (L+V), mono-phase vapor (V), and vapor-rich two-phase (V+L). The values of homogenization temperature (Th) and salinity of the analyzed liquid-rich two-phase fluid inclusions vary from 80°C to 220ºC and 6 to 13 wt.% NaCl eq., respectively (Fig. 11A, C). Given the Th and salinity values of the fluid inclusions, ore-forming hydrothermal fluids during development of the quartz vein-veinlets at Gharehkand experienced hydrostatic pressures within the range of 20-25 bars. This is almost equivalent to depths of 200-250 meters below the underground water table level. It is consistent with the estimated depths of most epithermal deposits (Bodnar et al., 2014). The Gharehkand microthermometric data points on the bivariate plot of Th versus salinity (Wilkinson, 2001) show that the densities of fluid inclusions vary from 0.9 to 1 g/cm3. The occurrence of boiling and simple cooling are the most effective mechanisms in deposition of ore and gangue minerals at Gharehkand. The Gharehkand microthermometric data points on the bivariate plot of Th versus salinity (Pirajno, 2009) indicate that the bisulfide complexing ligand most likely played the important role in transporting ore metals (particularly gold). Acknowledgements This research study was financially supported by the Research Bureau of the University of Tabriz. Therefore, the authors would like to express their gratitude to the authorities of this bureau. Our sincere thanks are also expressed to Dr. Behzad Hajalilu (faculty member of Geology Department at the Payame Noor University of Tabriz) for his bountiful cooperation during microscopic and microthermometric studies of fluid inclusions. Our appreciation is further extended to the anonymous reviewers for their valuable comments and suggestions on this manuscript. References Bodnar, R.J., Lecumberri-Sanchez P., Moncada D. and Steele-MacInnis M., 2014. Fluid Inclusions in Hydrothermal Ore Deposits. In: H.D. Holland and K.K. Turekian (Editors), Treatise on Geochemistry. Elsevier, Oxford, pp. 119–142. https://doi.org/10.1016/B978-0-08-095975-7.01105-0 Pirajno, F., 2009. Hydrothermal processes and mineral systems. Springer Science, New York, 1273 pp. http://doi:10.1007/978-1-4020/8613-7 Stocklin, J., 1968. Structural history and tectonic of Iran: A review. American Association of Petroleum Geologists Bulletin, 52(7): 1229–1258. https://doi.org/10.1306/5D25C4A5-16C1-11D7-8645000102C1865D Wilkinson, J.J., 2001. Fluid inclusions in hydrothermal ore deposits. Lithos, 55(1): 229–272. https://doi.org/10.1016/S0024-4937(00)00047-5

With the Upper Cambrian Xixiangchi Formation in the eastern Sichuan Basin as the target, this study investigates various diagenetic events during different diagenetic stages in deep dolomite reservoirs, accompanied by evaluations of their effects on the formation and evolution of the reservoir rock. A series of experiments are implemented on core and outcrop samples, including petrologic analysis, fluid inclusion analysis, rare earth and minor element investigation, and carbon and oxygen isotope test. During the syngenetic (syndepositional and penecontemporaneous) diagenesis stage, dolomitization is closely related to evaporation concentration and seepage reflux of high-salinity seawater, which facilitates the reservoir rock development by greatly enhancing the permeability of the reservoir. Meanwhile, a small number of secondary pores are generated in the sediments subjected to episodic atmospheric exposure and thus affected by meteoric water. During the early diagenesis stage, recrystallization transforms part of the granular dolomite into the crystalline dolomite with or without the phantom of the grain texture. It also alters the original rock’s pore structure and improves the effective primary porosity. Thus, recrystallization is key in forming the crystalline dolomite reservoir rock. However, compaction, cementation, and filling lead to the loss of massive early-formed primary pores and some secondary pores. During the mesodiagenesis-late diagenesis stage, the burial karstification, related to organic matter maturation, is the most direct control factor of the effective reservoirs space formation, and its alteration effect on the reservoir rock is related to the early process. This research helps to better identify the impact of various diagenetic processes during different diagenetic stages upon the formation and evolution of the deep dolomite reservoir rock, and it also helps analyze the relationships among these diagenetic processes. The findings of this research provide valuable references for investigating the formation mechanism of the deep dolomite reservoir rock in the Sichuan Basin.

Previous studies showed that the structure of Nanxiang Basin controlled the formation of oil and gas reservoirs, but the exact formation time of the reservoir and its coupling relationship with structural movement are not clear yet. Therefore, by analyzing the fluid inclusion system and combining with the projection method of burial history, this paper analyzed the times of oil and gas charging and accumulation in the Paleogene Hetaoyuan Formation of the Biyang Sag, and determined the age of oil and gas accumulation. The results showed that there were four phases of oil charging in two stages and one phase of natural gas charging in the Biyang Sag. The first stage mainly occurred during fault depression and uplift, including the first phase (36.1-23.5 Ma), the second phase (34.1-21.2 Ma) and the third phase (30.9-16.2 Ma) of oil charging, with the characteristics of multi-phase continuous charging. The second stage occurred during depression subsidence, including the fourth phase (7.9-0.2 Ma) of oil charging and the first phase (3.0-0.8 Ma) of natural gas charging. The early stage (the first phase) was the main formation time of oil and gas reservoirs in the Biyang Sag. The charging time of oil and gas was different in different structural zones in the Biyang Sag. The central deep subsided area and the southern slope were closer to the hydrocarbon-generating center, and were charged earlier, while the northern slope was charged relatively late. Therefore, it is recommended to focus on strengthening the vertical multi-layer and multi-stage three-dimensional exploration in the southern part of the Biyang Sag, strengthening the exploration of subtle lithology in the center, and focusing on the exploration of secondary or adjusted structural reservoirs in the north.

Deep burial of sedimentary basins results in the development of complex diagenetic environments influenced by pressure, temperature, and metasomatic chemical processes. Fracture systems resulting from deep tectonic-related burial can provide archives of physio-chemical characteristics during burial helping unravel diagenetic events such as hydrocarbon migration and paleobarometry. The Early Triassic Montney Formation in the Western Canadian Sedimentary Basin is a highly productive unconventional hydrocarbon reservoir that has undergone multiple phases of tectonic-related burial and uplift resulting in the formation of a series of calcite-filled fracture systems. These fracture systems occur as vertical to sub-vertical fractures, brecciated zones, and horizontal bedding-plane parallel fractures that are rich in co-occurring, but not co-genetic aqueous and petroleum fluid inclusion assemblages. Fluid inclusion microthermometry, Raman spectroscopy, and stable isotope analysis of these fracture systems and host rock reveals paleobarometric and temperature conditions during fracture formation. Vertical fractures formed at temperatures exceeding 142°C during peak burial associated with the Laramide orogeny ∼50 Ma. Similarities in modeled oxygen isotope values of calcite parent fluids and pore water implicate locally sourced carbonate in fracture calcite. Therefore, low permeability and closed system-like conditions were prevalent throughout initial fracture formation and cementation. Petrographic analysis of brecciated and horizontal fractures show evidence of hydrocarbon generation and migration into fracture-filling calcite. Modeling of petroleum inclusion paleobarometry indicates entrapment pressures approaching or even exceeding lithostatic pressure consistent with the development of overpressure associated with the thermal maturation of organic matter following peak burial. Combined use of aqueous and petroleum fluid inclusions in this deeply buried sedimentary system offers a powerful tool for better understanding diagenetic fluid flow, the timing of hydrocarbon migration/maturation, and helps constrain the pressure-temperature history important for characterizing economically important geologic formations.

Multi-stage hydrocarbon generation and accumulation are very common in petroliferous basins. Also, determination of hydrocarbon accumulation stages and each related diagenetic feature is important for understanding the distribution of current oil and gas resources in one individual basin. However, in the case of conventional sandstone reservoirs, few studies have focused on these resulting reservoir features (e.g., physical property and wettability) that are caused by the first accumulation of hydrocarbons and their geological implications. In this study, taking the reservoir from the Eocene Dongying Depression as an example, we investigated the features of the early hydrocarbon accumulation and its effects on the late accumulation, by analyzing the early accumulation-related paragenesis, fluid inclusions, clay minerals content, reservoir physical property, and wettability in sandstones. Our results show that the early stage accumulation of the overpressured hydrocarbon fluid could support and offset some loads of overburden, weaken the normal compaction, and preserve some original pores. Also, the early hydrocarbon accumulation resulted in an alternated, diagenetic fluid environment from the initial acidic to subsequent alkalic conditions, with the overall dissolution intensity stronger than the cementation, and formed a large number of secondary pores. As a result, the early accumulation was beneficial to reservoir space development and provided more space for the late hydrocarbons. In addition, the early hydrocarbon accumulation could cause the alteration of rock wettability and gradually formed a lipophilic migration pathway from the source rock to the reservoir. Also, the late stage of hydrocarbons would preferentially choose this dominant pathway for their migration (i.e., inheritance of migration pathway).

The petrographic characteristics of fluid inclusions of the main gas-bearing intervals of the Upper Paleozoic in the Ordos Basin are analyzed by means of plane-polarized light, fluorescence microscopy, and microthermometry. With the burial history of the basin, the charging and enrichment of natural gas in low-permeability reservoirs are also studied through a comparison of parameters such as the homogenization temperature and freezing temperature of aqueous inclusions associated with hydrocarbon inclusions. A comprehensive analysis of the assemblage characteristics, components, and temperature of fluid inclusions of the Upper Paleozoic shows that the abundance, attitude, and composition of gaseous hydrocarbon inclusions can reflect petroleum enrichment in low-permeability reservoirs. The homogenization temperature and freezing temperature of aqueous inclusions associated with gaseous hydrocarbon inclusions show no obvious discontinuities, indicating that natural gas charging was a long and continuous process since the Late Triassic to Early Cretaceous (210–100 Ma) and natural gas accumulation mainly occurred during the Early Cretaceous (125–100 Ma).

Fine-grained sedimentary rock (FGSR) reservoirs in a deep-water sedimentary environment from the Late Triassic Yanchang Formation in the Ordos Basin in central China have huge potential for tight oil production. According to the comprehensive research of fluid inclusion experiment, scanning electron microscopy, cathodoluminescence, thin section identification, and whole rock analysis, the petrographic characteristics, fluorescence spectrum parameters, and the homogenization temperature of oil inclusions and associated brine inclusions in the FGSR reservoir were analyzed to explore the coupling relationship between densification characteristics and tight oil accumulation of the FGSR reservoir. The results show the FGSR reservoir diagenesis has experienced compaction, cementation, and multiple stages of dissolution. A comprehensive analysis of burial history shows that the Chang 7 Member FGSR reservoir in the study area has three phases of oil charging, corresponding to the geologic time range of 132–124, 120–102, and 98–97 Ma. The organic acid produced by the first-stage oil charging accelerated the dissolution of feldspar and cuttings, and the dissolution pores increased significantly. Then, the organic acid in the second-stage oil charging accelerated the dissolution, and the abnormally high hydrocarbon expulsion pressure inhibited the damage of compaction on the pores of FGSR reservoir. Finally, the thermal evolution degree of source rocks reached the highest in the third-stage oil charging. The constructive effect of large-scale organic acids on pores and the protective effect of the chlorite membrane on pores inhibited the densification process of the FGSR reservoir. In short, the FGSR reservoir has experienced a cyclical reservoir densification process of “reducing porosity–increasing porosity–preserving porosity.” The coupling of pore evolution and oil charging of the FGSR reservoir is the key to the extensive accumulation and large-scale reservoir formation of tight oil in the Chang 7 Member of the Yanchang Formation in the Zhenyuan area, southwest Ordos Basin. The significance of the study may help to understand the process of the tight oil accumulation and predict the tight oil of the FGSR reservoir distribution.

The Lower Paleozoic reservoir in the Micangshan tectonic zone is a new shale gas exploration area with excellent potential. However, the hydrocarbon migration and accumulation histories of this reservoir have not been thoroughly elucidated and urgently require further research. Fluid inclusions offer a unique and useful method to test for hydrocarbon migration, accumulation, composition and timing. This study integrated the hydrocarbon charge history using fluid inclusions in the Lower Cambrian to Neoproterozoic reservoir from the Micangshan tectonic zone. This work involves the delineation and analysis of fluid inclusions using the petrography, spectroscopy and microthermometry of fluid inclusions. Based on the fluid inclusion analyses combined with reservoir thermal history, timing estimates and charge models of the hydrocarbons were obtained. The formation of natural gas was multifactorial in the Lower Cambrian to Neoproterozoic petroleum system, and the gas in the Niutitang (ϵ1n) and Dengying (Z2d) reservoirs was mainly from oil cracking and dry gas, and gas in the Xiannvdong (ϵ1x) and Canglangpu (ϵ1c) reservoirs was abiogenic and formed in hydrothermal fluids by regional tectonothermal events. Three well-defined stages of hydrocarbon charge were identified in the petroleum system in the Micangshan tectonic zone. The stage of oil charge first began before the Early Permian (∼277 Ma); the stage of gas charge from oil cracking occurred in the Late Triassic to Early Jurassic (212 Ma-198 Ma); and the stage of gas charge from dry gas occurred in the Middle Jurassic (173 Ma-166 Ma). The gas of mixed origin from the Niutitang reservoir was stored in the nanoscale pores as a self-reservoir, rather than as an effective gas source for the overlying reservoirs.

Introduction The study area is located in the Khorasan Razavi Province, NW of Gonabad between 58° 33˝- 58 ° 38˝ to the east and 25° 34˝ - 25° 38˝ to the north. Geotectonically, the area is located in the northern part of the Lut Block. The Lut Block is the main metallogenic province in the east of Iran (Karimpour et al., 2012). There is a significant outcrop of Tertiary intermediate volcanic and pyroclastic rocks in the northwest of Gonabad. This region is rich in clay (kaolin) mineralization. The source of these kaolin deposits (argillic alteration) is related to a granitic dyke that intruded into the Shemshak Formation. Geology According to studies most of the rocks in this region are volcanic rocks which mainly consist of trachyte, andesite, trachyandesite, dacite, rhyodacite, pyroclastics rocks of agglomerate and tuff and some subvolcanic masses and dykes of acidic to intermediate compositions. Sedimentary rocks in the study area are slightly metamorphosed. The oldest metamorphic rock is exposed in the south- east of the study area which consists of Jurassic slates and quartzite. At this area green schist facies have led to the formation of slate and quartzite. The intrusive bodies, composition are monzogranite porphyry to diorite porphyry. The main fault zones which make specific types of structure are strike-slip. Alteration and mineralization The volcanic and subvolcanic rocks have been affected by hydrothermal fluids via the phenomenon which has caused alteration in the rocks. The alteration zones are propylitic, silicification, argillic, and quartz-sericite-pyrite. The silicification has occurred with higher intensity in the northern and central parts of the investigated area. Propylitic alteration has spread all over the area with higher intensity in the northwest and southern parts of the study area. The clay mineral deposits (argillic zones) have been mined. The mineralogical compositions of this clay deposits are quartz, kaolinite, dickite, montmorillonite and hematite. Materials and Methods Ten doubly polished wafers (0.3mm thick) of fluorite, barite and quartz crystals were prepared for fluid inclusion studies, and examined petrographically. They were studied using standard techniques (Roedder, 1984, 1992) and Linkam THM 600 heating–freezing stage (from -190 to 600 °C) mounted on an Olympus TH4–200 microscope stage at the Ferdowsi University of Mashhad, Iran. The accuracy is estimated to be ±0.2 °C on freezing, ±2 °C below 350 °C and about ±4 above 350 °C on heating. The salinity of the fluids trapped in fluid inclusions is calculated based on the temperature of final ice melting (Tm) and the equation of Bodnar (1993). Densities are calculated using the Flincor software according to microthermometric data (Brown and Lamb, 1989). Discussion Microthermometeric investigations were conducted on 126 fluid inclusions in two types of liquid-rich (L+V) fluids in silicified cap of Rokhsefid and Baghsia kaolin mines. Homogenization experiments revealed a temperature range of 186–326 °C for the studied inclusion. Salinity variations could not be determined because of the small amount of fluids. The homogenization temperature and depth of formation from the first type of inclusions are 186- 256°C and 250 meters, respectively. The second type of inclusions have Th between 275 to 326°C and are 500 meter in depth. Microthermometric study of fluid inclusions on quartz-sericite-pyrite and sulfide- silicified mineralization in Kalatehno indicates that two types of hydrothermal fluids were important in the formation of mineralization. These two types are involved. First, Th between 289- 354 °C, salinity range from 10.86 to 10.98 wt.% NaCl equivalent, and the average depth of about 600 meters. Second, Th between 266- 377°C, salinity ranges from 11.7 to 13.07 wt.% NaCl equivalent, and average depth of about 600 meters. Microthermometric study of the fluid inclusions in fluorite veins were conducted on fluorite, barite and quartz minerals. The results obtained from the fluorites indicate Th between 184- 360°C, and Salinity ranges from 0 to 3.2 wt.% NaCl equivalent. Fluid inclusion studies consisting of quartz veins and quartz- sulfide- copper carbonate in Kalatehno copper mineralization involve two types of fluids with homogenization temperatures and salinity range from 260- 300 °C and 1.5- 3.23 wt.% NaCl equivalent and 193- 240 °C and 4.1- 5.86 wt.% NaCl equivalent. Conclusion Fluid inclusion studies on fluorite samples have shown a temperature homogenizations (Th) between 186-326 °C. These studies indicate the average formation temperature of 280°C for argillic alteration. Fluid inclusion studies on Kalateno Cu mineralization show two types of mineralization fluids with the temperatures of 193 to 240 and 260 to 300°C with salinity between 1.5-3.23 wt. % 4.1- 5.86 wt.% NaCl equivalent, respectively. The temperature ranges obtained are similar to those of epithermal systems.

Introduction The Robaie copper area is located 95 kilometers South of Damghan in the Semnan province. The study area has coordinates between 54˚30΄37˝to 54˚30΄42.71˝ latitude and 35˚22΄29.41˝ to 35˚23΄47.54˝ longitude. Geotectonically, the study area is located in the central Iran and in the northern part of the Torud-Chahshirin volcanic-plutonic belt (Houshmandzadeh et al., 1978). The Torud-Chahshirin volcanic-plutonic belt is a Tertiary magmatism in central Iran which is composed of volcanic rocks with dominant andesite composition and granodiorite intrusive with dominant diorite composition (Fard et al., 2001). Torud-Chahshirin volcanic-plutonic belt has created a favorable geological situation for base metals such as copper, lead, zinc, gold, silver and other precious and base metals, such as the Robaie copper area, Chah Messi (Cu±Pb-Zn; Imamjome et al., 2009), Kuh-Zar (Cu-Au; Rohbakhsh et al., 2018) and other instances. The main objective of this study is geology, petrography, U-Pb zircon dating and Sr-Nd isotope and also alteration, mineralization, geochemistry and fluid inclusion in the study area. Materials and methods 60 samples were collected from the study area. Petrographic studies were done on 40 thin sections. Mineralization and paragnesis of the system were studied based on 10 polished-thin sections and 6 polished sections. The measurements were conducted on a Linkam THMSG 600 at the Ferdowsi University of Mashhad. REE (ICP-MS method-ACME Laboratory in Vancouver, Canada) elements were analyzed for 3 samples of diorite dykes. Eight sampels for geochemistry and four samples for fire assay were analyzed at the Zar Azma Company. U-Pb dating in zircon of diorite dyke was conducted by the ICP-MS method in the Arizona LaserChron Center. Sr and Nd isotopic compositions were determined at the Laboratório de Geologia Isotópica da Universidade de Aveiro, Portugal. Results The geology of the area is dominated by volcanic rocks (andesite and trachyandesite), which were intruded by diorite dykes. Alteration zones are propylitic, argillic, sericitic and carbonate. The Copper deposit in the study area occurs as ore veins situated along fault zone with NS-SW trending. Vein thickness varies from 1-5m. Vein thickness varies from 1-5m. The primary minerals are chalcopyrite, pyrite and chalcocite, covellite, bornite, malachite, azurite, hematite, goethite and limonite are secondary minerals. The amount of Cu is between 0.01 to 5.6 % and amount of Ag, Sb, Pb, Zn, As elements is low. The homogenization temperature (Th) values ranged from 165 to 300 oC. Salinities of ore-forming fluids ranged from 7 to 16 wt. % NaCl equivalents. Diorite dykes in the Robaie area have characteristics of enrichment in LREE versus HREE, enrichment of LILE and depletion in HFSE. The initial 87Sr/86Sr and 143Nd/144Nd ratios of biotite-hornblende diorite are 0.705664 and 0.512486, respectively. The εNdI value is -1.7. In the εNdI versus initial 87Sr/86Sr diagram diorite dykes of the Robaie area plot to the right part of the mantle array. The mean age of diorite dyke is 50.49±0.49 Ma. Therefore, the U-Th-Pb zircon dating indicates that diorite dyke formed in the early Eocene (Ypresian) era. Discussion Diorite dykes originated from mantle-derived magmas. The parental melt would have originated in a non-depleted mantle source. Isotopic data from diorite dykes show that subduction source with contamination to continental crust. In tectonic setting diagrams (Pearce et al., 1984) diorite dykes plot on the fields of the volcanic arc granites (VAG). In the Dy/Yb vs. Dy system (Shaw, 1970) diorite dykes of Robaie area were formed by 15-20% partial melting of spinel-phlogopite lherzolite. According to Yh/Yb vs. Ta/Yb (Pearce et al., 1984) and Ba/La vs. Th/Nd diagrams (Shaw, 1970) diorite dykes were formed from slab-drive fluid in the active continental margins. Fluid inclusions data of the Robaie area manifest that the ore-forming fluids were medium to low temperature and medium to low salinity. The pressure determined for the Robaie area was approximately < 10 MPa, which is equivalent to a depth of approximately < 1 km assuming lithostatic pressure. Fluid inclusion studies indicate that there is a positive correlation between homogenization temperature and fluid salinity, similar to the process of fluid mixing. The decrease in salinity has been the most important factor in the precipitation of copper in the area. All of evidence shows that mineralization in the Robaie area is of epithermal type deposit. Acknowledgment The financial support provided by grant no. 42842.3, date: 3 Jan 2017 is greatly appreciated. We would like to thank Mr. Ehsan Azizian of the Zamin Pouyan Fraz Assia Company for the generous support and the access to mine data.

Petrography microthermometry of fluid inclusion, quantitative grain fluorescence (QGF) and quantitative grain fluorescence on extract(QGF-E) are used to study the paleo-fluid characteristics and hydrocarbon charging history of Jurassic reservoir in Dibei gas field, Kuqa depression, Tarim Basin.The results show that the Jurassic reservoirs in Dibei gas field develop inclusions with two stages:the first stage is liquid inclusion with yellow-green color, which indicats the filling of early oil;the second stage is gas-liquid inclusion with blue-white fluorescence color and gas inclusions with non-fluorescence color, which indicats that the late gas was charged.The homogenization temperature of inclusions indicats the two stages of hydrocarbon charging. QGF and QGF-E show that the oil in the Jurassic reservoir of the Dibei gas field may be a mixture of different origins or different maturity.Combined with the sedimentary history of Dibei gas field, it is suggested that the Dibei gas field has experienced two stages of oil and gas charging.The first is the filling of oil between 18~16 Ma.Gas charging period in the second stage is 5~3 Ma.Since the Xiyu period, the tectonic movement has been strong and the gas field accumulate at low parts.

ABSTRACT: The Lower Cretaceous Yingcheng Formation in the southern Songliao Basin is the typical tight oil sandstone in China. In order to better predict the petrophysical properties of the tight sandstone reservoirs in the Lower Cretaceous Yingcheng Formation, Songliao Basin, Northeast China, the diagenesis and porosity evolution was investigated using a suite of petrographic and geochemical techniques including thin section analysis, scanning electron microscopy, mercury intrusion and fluid inclusion analysis, on a set of selected tight sandstone samples. Combined with the histories of burial evolution, organic matter thermal evolution and hydrocarbon charge, the matching relationship between reservoir porosity evolution and hydrocarbon accumulation history is analyzed. The result showed that the tight sandstone reservoirs characterized of being controlled by deposition, predominated by compaction, improved by dissolution and enhanced by cementation. The hydrocarbon accumulation period was investigated using a suite of hydrocarbon generation and expulsion history, microfluorescence determination and temperature measurement technology. According to the homogenization temperature of the inclusions and the history of burial evolution, Yingcheng Formation has mainly two phases hydrocarbon accumulation. The first phase of oil and gas is charged before the reservoir is tightened, the oil and gas generated by Shahezi source rocks enter the sand body of Yingcheng Formation, influenced by the carrying capability of sand conducting layer, oil and gas is mainly conducted by the better properties and higher connectivity sand body and enriched in the east, which belongs to the type of densification after hydrocarbon accumulation. The second phase of oil and gas charge after densification, which belongs to the type of densification before the hydrocarbon accumulation.

Abstract Beryl is usually found in granite-pegmatite systems. The addition of chromophore elements (V, Cr, Mn, Fe) into the crystalline structure favors color changes in beryl and thus generates some of the world’s expensive gems such as emerald, morganite, heliodor and aquamarine. The Massangana polyphasic batholith is a well-known cassiterite, wolframite and gems deposit in the Rondônia state. These metals and blue-gems (topaz and aquamarine) are located in feldspar-rich pegmatite granite bodies. The aquamarine crystals show color ranging from light- to medium-blue and display concentric growth zones. Electron-probe microanalyses revealed that the Fe is the main chromophore element, occupying the octahedral Al-site, while Na had an important role in the charge balance, inserted in the channel sites together with H2O. The irregular supply of Fe and Na during the nucleation and growth of aquamarine was the main cause for the color change. A fluid inclusion study indicated that the aquamarine growth under an aqueous fluid system (H2O-NaCl), with low salinity, low density and total homogenization temperature between 243º-315º C, is compatible with final temperatures in the pegmatite pocket zone.

The Junggar Basin is rich in natural gas resources, but it has hardly been explored, with the proven rate being less than 9.0%. Although the hinterland of the Junggar Basin has a favorable condition for natural gas accumulation, the complex gas sources cause great trouble in the selection of zones and belts for exploration. Based on the molecular composition and stable carbon and hydrogen isotope data of 95 natural gas samples from 72 wells in this area, combined with the characteristics of structural evolution history, burial history, hydrocarbon generation and expulsion history, and fluid inclusions, this paper clarified the geneses and sources of natural gas, identified the secondary alteration of natural gas, and restored the process of natural gas accumulation. Natural gas in the hinterland was divided into four types: Type I was oil-type gas from the Lower Permian Fengcheng Formation; Type II was coal-type gas derived from the Carboniferous source rock; Type III was the mixture of Type I and II gases, which constituted the major fraction of natural gases in the hinterland; and Type IV that referred to secondary microbial gas formed by the biodegradation of crude oil. During the Late Cretaceous, the Carboniferous and Fengcheng source rocks entered the gas generation peak and a series of natural gas reservoirs were formed. However, affected by the later tectonic movements, some gas reservoirs were damaged or adjusted, and natural gas leakage and biodegradation occurred. This study has shifted the focus of natural gas exploration in the study area from the petroleum system associated with the Middle Permian source rocks to that with the Lower Permian and Carboniferous source rocks, which is of great significance for natural gas exploration in the Junggar Basin. Further, it provides an example to identify the geneses and sources of natural gas under complex conditions based on integrated geological and geochemical assessments.

An equation of state (EOS) of CH4-N2 fluid mixtures in terms of Helmholtz free energy has been developed by using four mixing parameters, which can reproduce the pressure-volume-temperature-composition (PVTx) and vapor-liquid equilibrium (VLE) properties of CH4-N2 fluid mixtures. The average absolute deviation of all the PVTx data available up to 673.15 K and 1380 bar from this EOS is 0.38%. Combining this EOS of CH4-N2 fluid mixtures and the EOS of CH4-CO2 and CO2-N2 fluid mixtures in our previous work, an EOS of CO2-CH4-N2 fluid mixtures has been developed, which is named ZMS EOS. The ZMS EOS can calculate all thermodynamic properties of ternary CO2-CH4-N2 fluid mixtures and the average absolute deviation of the PVTx data from the ZMS EOS is 0.40% for the CO2-CH4-N2 system. The ZMS EOS can be applied to calculate excess enthalpies of CO2-CH4-N2 fluid mixtures, predict the solubility of CO2-CH4-N2 fluid mixtures in brine and water, and quantitatively estimate the impact of the impurities (CH4 and N2) on the CO2 storage capacity in the CO2 capture and storage (CCS) processes. The ZMS EOS can also be applied to calculate the isochores of CO2-CH4-N2 system in the studies of fluid inclusions. All Fortran computer codes and Origin drawing projects in this paper can be obtained freely from the corresponding author.