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Abstract:The study of fluid inclusions can help constrain the conditions at which diagenetic minerals precipitated, leading to a better understanding of the geologic controls and relative timing of changes in porosity and/or mineralising events. Many of the diagenetic minerals are easily deformed and it is important to check for any post-entrapment changes to the inclusions. Possible post-entrapment changes include reaction with the host crystal, necking down, nucleation metastability and thermal re-equilibration. The recommended method of detecting these problems is to examine individual fluid inclusion assemblages (FIAs) and report data for each individual FIA. These studies have been enhanced by the development of new micro-analytical techniques such as micro-fluorescence spectroscopy, micro-infrared spectroscopy, nuclear magnetic resonance, various mass spectrometry techniques and the analysis of individual fluid inclusions using laser ablation/decrepitation methods. Special techniques have been developed for hydrocarbon-bearing inclusions such as the Grains containing Oil Inclusions (GOI), Fluid Inclusion Stratigraphy (FIS), and the Molecular Composition of Inclusions (MCI) techniques. The fluid inclusions that form in some minerals during diagenesis provide the only direct means of examining the fluids present in these systems. They provide useful temperature, pressure, and fluid composition data that cannot be obtained by other means.

Abstract:Re-equilibration of fluid inclusions in crystals takes place by loss or gain of solvents and solutes from fluid inclusions and by changes in their volumes. Volume change of fluid inclusions are primarily dictated by elastic properties and available slip planes of host crystals. In the present study, the phase-behavior of fluids entrapped in co-precipitated calcite and barite is studied. While calcite contains only biphase fluid inclusions, barite has predominantly monophase fluid inclusions. Fluid inclusion petrography, microthermometry and leachate analysis are used to establish the nature of entrapped fluids and entrapment temperature is substantiated through independent sulfur isotope geothermometry using coexisting barite and pyrite. Phase transitions in the monophase fluid inclusions in barite are explained in terms of over-pressuring of fluids in these fluid inclusions relative to fluids entrapped in calcite owing to the low bulk modulus of barite.

Abstract:The Hujiayu Cu deposit, representative of the “HuBi-type” Cu deposits in the Zhongtiao Mountains district in the southern edge of the North China Craton, is primarily hosted in graphite-bearing schists and carbonate rocks. The ore minerals comprise mainly chalcopyrite, with minor sphalerite, siegenite [(Co,Ni)3S4], and clausthalite [Pb(S,Se)]. The gangue minerals are mainly quartz and dolomite, with minor albite. Four fluid inclusion types were recognized in the chalcopyrite-pyrite-dolomite-quartz veins, including CO2-rich inclusions (type I), low-salinity, liquid-dominated, biphase aqueous inclusions (type II), solid-bearing aqueous inclusions (type III), and solid-bearing aqueous-carbonic inclusions (type IV). Type I inclusion can be further divided into two sub-types, i.e., monophase CO2 inclusions (type Ia) and biphase CO2-rich inclusions (with a visible aqueous phase), and type III inclusion is divided into a subtype with a halite daughter mineral (type IIIa) and a subtype with multiple solids (type IIIb). Various fluid inclusion assemblages (FIAs) were identified through petrographic observations, and were classified into four groups. The group-1 FIA, consisting of monophase CO2 inclusions (type Ia), homogenized into the liquid phase in a large range of temperatures from ?1 to 28°C, suggesting post-entrapment modification. The group-2 FIA consists of type Ib, IIIb and IV inclusions, and is interpreted to reflect fluid immiscibility. The group-3 FIA comprises type II and IIIa inclusions, and the group-4 FIA consists of type II inclusions with consistent phase ratios. The group-1 and group-2 FIAs are interpreted to be entrapped during mineralization, whereas group-3 and group-4 FIAs probably represent the post-mineralization fluids. The solid CO2 melting temperatures range from ?60.6 to 56.6°C and from ?66.0 to ?63.4°C for type Ia and type IV inclusions, respectively. The homogenization temperatures for type II inclusions range from 132 to 170°C for group-3 FIAs and 115 to 219°C for group-4 FIAs. The halite melting temperatures range from 530 to 562°C for type IIIb and IV inclusions, whereas those for type IIIa inclusions range from 198 to 398°C. Laser Raman and SEM-EDS results show that the gas species in fluid inclusions are mainly CO2 with minor CH4, and the solids are dominated by calcite and halite. The calcite in the hosting marble and dolomite in the hydrothermal veins have δ13CV-PDB values of ?0.2 to 1.2‰ and ?1.2 to ?6.3‰, and δ18OV-SMOW values of 14.0 to 20.8 ‰ and 13.2 to 14.3 ‰, respectively. The fluid inclusion and carbon-oxygen isotope data suggest that the ore-forming fluids were probably derived from metamorphic fluids, which had reacted with organic matter in sedimentary rocks or graphite and undergone phase separation at 1.4–1.8 kbar and 230–240°C, after peak metamorphism. It is proposed that the Hujiayu Cu deposit consists of two mineralization stages. The early stage mineralization, characterized by disseminated and veinlet copper sulfides, probably took place in an environment similar to sediment-hosted stratiform copper mineralization. Ore minerals formed in this precursor mineralization stage were remobilized and enriched in the late metamorphic hydrothermal stage, leading to the formation of thick quartz–dolomite–sulfides veins.

Abstract:: The Datuanshan deposit is one of the largest and most representative stratabound copper deposits in the Tongling area, the largest ore district in the Middle–Lower Yangtze River metallogenic belt. The location of the orebodies is controlled by the interlayer–slipping faults between the Triassic and Permian strata, and all the orebodies are distributed in stratiform shape around the Mesozoic quartz monzodiorite dikes. Based on field evidence and petrographic observations, four mineralization stages in the Datuanshan deposit have been identified: the skarn, early quartz–sulfide, late quartz–sulfide and carbonate stages. Chalcopytite is the main copper mineral and mainly formed at the late quartz–sulfide stage. Fluid inclusions at different stages were studied for petrography, microthermometry, laser Raman spectrometry and stable isotopes. Four types of fluid inclusions, including three-phase fluid inclusions (type 1), liquid-rich fluid inclusions (type 2), vapour–rich fluid inclusions (type 3) and pure vapour fluid inclusions (type 4), were observed. The minerals from the skarn, early and late quartz–sulfide stages contain all fluid inclusion types, but only type 2 fluid inclusions were observed at the carbonate stage. Petrographic observations suggest that most of the inclusions studied in this paper are likely primary. The coexistence of different types of fluid inclusions with contrasting homogenization characteristics (to the liquid and vapour phase, respectively) and similar homogenization temperatures (the modes are 440–480°C, 380–400°C and 280–320°C for the skarn, early and late quartz–sulfide stages, respectively) in the first three stages, strongly suggests that three episodes of fluid boiling occurred during these stages, which is supported by the hydrogen isotope data. Laser Raman spectra identified CH4 at the skarn and early quartz–sulfide stages. Combined with other geological features, the early ore–forming fluids were inferred to be under a relatively reduced environment. The CO2 component has been identified at the late quartz–sulfide and carbonate stages, indicating that the late ore-forming fluids were under a relatively oxidized environment, probably as a result of inflow of and mixing with meteoric water. In addition, microthermometric results of fluid inclusions and H–O isotope data indicate that the ore forming fluids were dominated by magmatic water in the early stages (skarn and early quartz–sulfide stages) and mixed with meteoric water in the late stages (late quartz–sulfide and carbonate stages). The evidence listed above suggests that the chalcopyrite deposition in the Datuanshan deposit probably resulted from the combination of multi-episode fluid boiling and mixing of magmatic and meteoric water.

Abstract:The Tongcun Mo (Cu) deposit in Kaihua city of Zhejiang Province, eastern China, occurs in and adjacent to the Songjiazhuang granodiorite porphyry and is a medium-sized and important porphyry type ore deposit. Two irregular Mo (Cu) orebodies consist of various types of hydrothermal veinlets. Intensive hydrothermal alteration contains skarnization, chloritization, carbonatization, silicification and sericitization. Based on mineral assemblages and crosscutting relationships, the ore-forming processes are divided into five stages, i.e., the early stage of garnet + epidote ± chlorite associated with skarnization and K-feldspar + quartz ± molybdenite veins associated with potassic-silicic alteration, the quartz-sulfides stage of quartz + molybdenite ± chalcopyrite ± pyrite veins, the carbonatization stage of calcite veinlets or stockworks, the sericite + chalcopyrite ± pyrite stage, and the late calcite + quartz stage. Only the quartz-bearing samples in the early stage and in the quartz-sulfides stage are suitable for fluid inclusions (FIs) study. Four types of FIs were observed, including 1) CO2-CH4 single phase FIs, 2) CO2-bearing two- or three-phase FIs, 3) Aqueous two-phase FIs, and 4) Aqueous single phase FIs. FIs of the early stages are predominantly CO2- and CH4-rich FIs of the CO2-CH4-H2O-NaCl system, whereas minerals in the quartz-sulfides stage contain CO2-rich FIs of the CO2-H2O-NaCl system and liquid-rich FIs of the H2O-NaCl system. For the CO2-CH4 single phase FIs of the early mineralization stage, the homogenization temperatures of the CO2 phase range from 15.4 °C to 25.3 °C (to liquid), and the fluid density varies from 0.7 g/cm3 to 0.8 g/cm3; for two- or three-phase FIs of the CO2-CH4-H2O-NaCl system, the homogenization temperatures, salinities and densities range from 312°C to 412°C, 7.7 wt% NaCl eqv. to 10.9 wt% NaCl eqv., and 0.9 g/cm3 to 1.0 g/cm3, respectively. For CO2-H2O-NaCl two- or three-phase FIs of the quartz-sulfides stage, the homogenization temperatures and salinities range from 255°C to 418°C, 4.8 wt% NaCl eqv. to 12.4 wt% NaCl eqv., respectively; for H2O-NaCl two-phase FIs, the homogenization temperatures range from 230 °C to 368 °C, salinities from 11.7 wt% NaCl eqv. to 16.9 wt% NaCl eqv., and densities from 0.7 g/cm3 to 1.0 g/cm3. Microthermometric measurements and Laser Raman spectroscopy analyses indicate that CO2 and CH4 contents and reducibility (indicated by the presence of CH4) of the fluid inclusions trapped in quartz-sulfides stage minerals are lower than those in the early stage. Twelve molybdenite separates yield a Re-Os isochron age of 163 ± 2.4 Ma, which is consistent with the emplacement age of the Tongcun, Songjiazhuang, Dayutang and Huangbaikeng granodiorite porphyries. The δ18OSMOW values of fluids calculated from quartz of the quartz-sulfides stage range from 5.6‰ to 8.6‰, and the δDSMOW values of fluid inclusions in quartz of this stage range from –71.8‰ to –88.9‰, indicating a primary magmatic fluid source. δ34SV-CDT values of sulfides range from +1.6‰ to +3.8‰, which indicate that the sulfur in the ores was sourced from magmatic origins. Phase separation is inferred to have occurred from the early stage to the quartz-sulfides stage and resulted in ore mineral precipitation. The characteristics of alteration and mineralization, fluid inclusion, sulfur and hydrogen-oxygen isotope data, and molybdenite Re-Os ages all suggest that the Tongcun Mo (Cu) deposit is likely to be a reduced porphyry Mo (Cu) deposit associated with the granodiorite porphyry in the Tongcun area.

Abstract:The Mayuan stratabound Pb-Zn deposit in Nanzheng, Shaanxi Province, is located in the northern margin of the Yangtze Plate, in the southern margin of the Beiba Arch. The orebodies are stratiform and hosted in breciated dolostone of the Sinian Dengying Formation. The ore minerals are primarily sphalerite and galena, and the gangue minerals comprise of dolomite, quartz, barite, calcite and solid bitumen. Fluid inclusions from ore-stage quartz and calcite have homogenization tempreatures from 98 to 337oC and salinities from 7.7 wt% to 22.2 wt% (NaCl equiv.). The vapor phase of the inclusions is mainly composed of CH4 with minor CO2 and H2S. The δDfluid values of fluid inclusions in quartz and calcite display a range from ?68‰ to ?113‰ (SMOW), and the δ18Ofluid values calculated from δ18Oquartz and δ18Ocalcite values range from 4.5‰ to 16.7‰ (SMOW). These data suggest that the ore-forming fluids may have been derived from evaporitic sea water that had reacted with organic matter. The δ13CCH4 values of CH4 in fluid inclusions range from ?37.2‰ to ?21.0‰ (PDB), suggesting that the CH4 in the ore-forming fluids was mainly derived from organic matter. This, together with the abundance of solid bitumen in the ores, suggest that organic matter played an important role in mineralization, and that the thermochemical sulfate reduction (TSR) was the main mechanism of sulfide precipitation. The Mayuan Pb-Zn deposit is a carbonate-hosted epigenetic deposit that may be classified as a Mississippi Valley type (MVT) deposit.

Abstract:The Talate Pb–Zn deposit, located in the east of the NW–SE extending Devonian Kelan volcanic-sedimentary basin of the southern Altaides, occurs in the metamorphic rock series of the upper second lithological section of the lower Devonian lower Kangbutiebao Formation (D1k12). The Pb–Zn orebodies are stratiform and overprinted by late sulfide–quartz veins. Two distinct mineralization periods were identified: a submarine volcanic sedimentary exhalation period and a metamorphic hydrothermal mineralization period. The metamorphic overprinting period can be further divided into two stages: an early stage characterized by bedding-parallel lentoid quartz veins developed in the chlorite schist and leptite of the ore-bearing horizon, and a late stage represented by pyrite–chalcopyrite–quartz veins crosscutting chlorite schist and leptite or the massive Pb–Zn ores. Fluid inclusions in the early metamorphic quartz veins are mainly CO2–H2O–NaCl and carbonic (CO2±CH4±N2) inclusions with minor aqueous inclusions. The CO2–H2O–NaCl inclusions have homogenization temperatures of 294–368°C, Tm,CO2 of ?62.6 to ?60.5°C, Th,CO2 of 7.7 to 29.6°C (homogenized into liquid), and salinities of 5.5–7.4 wt% NaCl eqv. The carbonic inclusions have Tm, CO2 of ?60.1 to ?58.5°C, and Th, CO2 of ?4.2 to 20.6°C. Fluid inclusions in late sulfide quartz veins are also dominated by CO2–H2O–NaCl and CO2±CH4 inclusions. The CO2–H2O–NaCl inclusions have Th,tot of 142 to 360°C, Tm,CO2 of ?66.0 to ?56.6°C, Th,CO2 of ?6.0 to 29.4°C (homogenized into liquid) and salinities of 2.4–16.5 wt% NaCl eqv. The carbonic inclusions have Tm, CO2 of ?61.5 to ?57.3°C, and Th, CO2 of ?27.0 to 28.7°C. The aqueous inclusions (L-V) have Tm,ice of ?9.8 to ?1.3°C and Th,tot of 205 to 412°C. The P–T trapping conditions of CO2-rich fluid inclusions (100–370 MPa, 250–368°C) are comparable with the late- to post-regional metamorphism conditions. The CO2-rich fluids, possibly derived from regional metamorphism, were involved in the reworking and metal enrichment of the primary ores. Based on these results, the Talate Pb–Zn deposit is classified as a VMS deposit modified by metamorphic fluids. The massive Pb–Zn ores with banded and breccia structures were developed in the early period of submarine volcanic sedimentary exhalation associated with an extensional subduction-related back-arc basin, and the quartz veins bearing polymetallic sulfides were formed in the late period of metamorphic hydrothermal superimposition related to the Permian–Triassic continental collision.

Abstract:The Zhaxikang Pb-Zn-Sb polymetallic deposit is one of the most important deposits in the newly recognized southern Tibet antimony-gold metallogenic belt. Compared to the porphyry deposits in the Gangdese belt, much less researches have addressed these deposits, and the genesis of the Zhaxikang deposit is still controversial. Based on field investigation, petrographic, microthermometric, Laser Raman Microprobe (LRM) and SEM/EDS analyses of fluid, melt-fluid, melt and solid inclusions in quartz and beryl from pegmatite, this paper documents the characteristics and the evolution of primary magmatic fluid which was genetically related to greisenization, pegmatitization, and silification in the area. The results show that the primary magmatic fluids were derived from unmixing between melt and fluid and underwent a phase separation process soon after the exsolution. The primary magmatic fluids are of low salinity, high temperature, and can be approximated by the H2O-NaCl-CO2 system. The presence of Mn-Fe carbonate in melt-fluid inclusions and a Zn-bearing mineral (gahnite) trapped in beryl and in inclusions from pegmatite indicates high Mn, Fe, and Zn concentrations in the parent magma and magmatic fluids, and implies a genetic link between pegmatite and Pb-Zn-Sb mineralization. High B and F concentrations in the parent magma largely lower the solidus of the magma and lead to late fluid exsolution, thus the primary magmatic fluids related to pegmatite have much lower temperature than those in most porphyry systems. Boiling of the primary magmatic fluids leads to high-salinity and high-temperature fluids which have high capacity to transport Pb, Zn and Sb. The decrease in temperature and mixing with fluids from other sources may have caused the precipitation of Pb-Zn-Sn (Au) minerals in the distal fault systems surrounding the causative intrusion.

Abstract:The Dahutang tungsten polymetallic ore field is located north of the Nanling W–Sn polymetallic metallogenic belt and south of the Middle–Lower Yangtze River Valley Cu–Mo–Au–Fe porphyry-skarn belt. It is a newly discovered ore field, and probably represents the largest tungsten mineralization district in the world. The Shimensi deposit is one of the mineral deposits in the Dahutang ore field, and is associated with Yanshanian granites intruding into a Neoproterozoic granodiorite batholith. On the basis of geologic studies, this paper presents new petrographic, microthermometric, laser Raman spectroscopic and hydrogen and oxygen isotopic studies of fluid inclusions from the Shimensi deposit. The results show that there are three types of fluid inclusions in quartz from various mineralization stages: liquid-rich two-phase fluid inclusions, vapor-rich two-phase fluid inclusions, and three-phase fluid inclusions containing a solid crystal, with the vast majority being liquid-rich two-phase fluid inclusions. In addition, melt and melt-fluid inclusions were also found in quartz from pegmatoid bodies in the margin of the Yanshanian intrusion. The homogenization temperatures of liquid-rich two-phase fluid inclusions in quartz range from 162 to 363°C and salinities are 0.5wt%–9.5wt% NaCl equivalent. From the early to late mineralization stages, with the decreasing of the homogenization temperature, the salinity also shows a decreasing trend. The ore-forming fluids can be approximated by a NaCl–H2O fluid system, with small amounts of volatile components including CO2, CH4 and N2, as suggested by Laser Raman spectroscopic analyses. The hydrogen and oxygen isotope data show that δDV-SMOW values of bulk fluid inclusions in quartz from various mineralization stages vary from ?63.8‰ to ?108.4‰, and the δ18OH2O values calculated from the δ18OV-SMOW values of quartz vary from ?2.28‰ to 7.21‰. These H–O isotopic data are interpreted to indicate that the ore-forming fluids are mainly composed of magmatic water in the early stage, and meteoric water was added and participated in mineralization in the late stage. Integrating the geological characteristics and analytical data, we propose that the ore-forming fluids of the Shimensi deposit were mainly derived from Yanshanian granitic magma, the evolution of which resulted in highly differentiated melt, as recorded by melt and melt-fluid inclusions in pegmatoid quartz, and high concentrations of metals in the fluids. Cooling of the ore-forming fluids and mixing with meteoric water may be the key factors that led to mineralization in the Dahutang tungsten polymetallic ore field.

Abstract:The barium deposits in Ankang and Xunyang counties, Shaanxi Province, China, occur in the northernmost part of the world-class barium metallogenic belt in south Qinling. The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks, with a unique combination of barite and witherite. The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 °C, whereas those from the witherite have two peaks of 165–175 °C, and 215–225 °C, respectively. Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H2O, although some contains N2, H2S, and CH4. The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members, one dominated by H2O without other volatiles, and the other containing CH4, C2H6, C3H8, C2H4, and C6H6 in addition to H2O. CO2, H2S, and some CH4 are interpreted as products of chemical reactions during mineralization. Organic gases (CH4, C2H6, C3H8, C2H4, and C6H6) in the fluids were critical in the formation of barium sulfate versus carbonate. The δ34S values of barite range from 38.26‰ to 54.23‰ (CDT), the δ34S values of sulfides coexisting with barium minerals vary from 22.44‰ to 25.11‰ (CDT), and those in the wall rock from 11.60‰ to 19.06‰ (CDT). We propose that the SO42– generally experienced bacterial sulfate reduction in seawater before mineralization, and some SO42– also experienced thermochemical sulfate reduction in hydrothermal system during mineralization. The δ13C values of witherite range from ?27.30‰ to ?11.80‰ (PDB), suggesting that carbon was sourced from organic substances (like CH4, C2H4, and C2H6). The formation of witherite was possibly associated with thermochemical sulfate reduction, which caused the consumption of the organic gases and SO42– in the hydrothermal solutions, consequently inhibiting barite formation. The important conditions for forming witherite include high fluid temperatures, high Ba2+ concentrations, CO2 in the fluids, low HS– concentrations, and the subsequent rapid diffusion of H2S during thermochemical sulfate reduction of the fluids.

Abstract:Field investigation combined with detailed petrographic observation indicate that abundant oil, gas, and solid bitumen inclusions were entrapped in veins and cements of sedimentary rocks in the Dabashan foreland, which were used to reconstruct the oil and gas migration history in the context of tectonic evolution. Three stages of veins were recognized and related to the collision between the North China block and the Yangtze block during the Indosinian orogeny from Late Triassic to Early Jurassic (D1), the southwest thrusting of the Qinling orogenic belt towards the Sichuan basin during the Yanshanian orogeny from Late Jurassic to Early Cretaceous (D2), and extensional tectonics during Late Cretaceous to Paleogene (D3), respectively. The occurrences of hydrocarbon inclusions in these veins and their homogenization temperatures suggest that oil was generated in the early stage of tectonic evolution, and gas was generated later, whereas solid bitumen was the result of pyrolysis of previously accumulated hydrocarbons. Three stages of hydrocarbon fluid inclusions were also identified in cements of carbonates and sandstones of gas beds in the Dabashan foreland belt and the Dabashan foreland depression (northeastern Sichuan basin), which recorded oil/gas formation, migration, accumulation and destruction of paleo-reservoirs during the D2. Isotopic analysis of hydrocarbon fluid inclusions contained in vein minerals shows that δ13C1 of gas in fluid inclusions ranges from ?17.0‰ to ?30.4‰ (PDB) and δD from ?107.7‰ to ?156.7‰ (SMOW), which indicates that the gas captured in the veins was migrated natural gas which may be correlated with gas from the gas-fields in northern Sichuan basin. Organic geochemical comparison between bitumen and potential source rocks indicates that the Lower Cambrian black shale and the Lower Permian black limestone were the most possible source rocks of the bitumen. Combined with tectonic evolution history of the Dabashan foreland, the results of this study suggest that oil was generated from the Paleozoic source rocks in the Dabashan area under normal burial thermal conditions before Indosinian tectonics and accumulated to form paleo-reservoirs during Indosinian collision between the North China block and the Yangtz block. The paleo-reservoirs were destroyed during the Yanshanian tectonic movement when the Dabashan foreland was formed. At the same time, oil in the paleo-reservoirs in the Dabashan foreland depression was pyrolyzed to transform to dry gas and the residues became solid bitumen.

Abstract:Petrographic analysis of hydrocarbon inclusions in reservoirs is the basis and prerequisite for study of hydrocarbon charge history using fluid inclusion analysis. Samples from Silurian reservoirs in the Kongquehe area were studied with microscopy, cathode luminescence and scanning electron microscopy, and the paragenetic sequence of diagenetic events was established. Aqueous and oil inclusions were found in four different occurrences, i.e., ① in healed cracks in detrital quartz grains, ② in quartz overgrowths that were formed relatively early in diagenesis, ③ in healed cracks crosscutting quartz overgrowths and detrital quartz, and ④ in paragenetically late calcite cements. Solid bitumens were found in intergranular pores and in late fractures, whereas gas inclusions occur in healed cracks crosscutting quartz overgrowths and detrital quartz. The homogenization temperatures of aqueous (Thaq) and oil incluisons (Tho) within individual fluid inclusion assemblages are very consistent, suggesting that the microthermometric data are reliable. The Thaq values are generally larger than Tho, indicating the oil charging events took place at significant depths. The results suggest that there were at least two episodes of hydrocarbon charging in the Kongquehe area: the early hydrocarbon charging occurred in late Caledonian, dominated by oil, and the late hydrocarbon charging occurred in the Yanshan-Himalayan, first by oil and then gases. In addition, two episodes of hydrocarbon reservoir adjustment and destruction occurred in the Hercynian and Himalayan, respectively, forming solid bitumen.

Abstract:This work aims to quantify sulfate ion concentrations in the system Na2SO4-H2O using Raman micro-spectroscopy. Raman spectra of sodium sulfate solutions with known concentrations were collected at ambient temperature (293 K) and in the 500 cm?1–4000 cm?1 spectral region. The results indicate that the intensity of the SO42? band increases with increasing concentrations of sulfate ion. A linear correlation was found between the concentration of SO42? (c) and parameter I1 ,which represents the ratio of the area of the SO42? band to that of the O-H stretching band of water (As / Aw): I1=?0.00102+0.01538c. Furthermore, we deconvoluted the O-H stretching band of water (2800 cm?1–3800 cm?1) at 3232 and 3430 cm?1 into two sub-Gaussian bands, and then defined Raman intensity of the two sub-bands as AB1 (3232 cm?1) and AB2 (3430 cm?1), defined the full width of half maximum (FWHM) of the two sub-bands as WB1 (3232 cm?1) and WB2 (3430 cm?1). A linear correlation between the concentration of SO42?(c) and parameter I2, which represents the ratio of Raman intensity of SO42?(As) (in 981 cm-1) to (AB1+AB2), was also established: I2=?0.0111+0.3653c. However, no correlations were found between concentration of SO42?(c) and FWHM ratios, which includes the ratio of FWHM of SO42?(Ws) to WB1, WB2 and WB1+B2 (the sum of WB1 and WB2), suggesting that FWHM is not suitable for quantitative studies of sulfate solutions with Raman spectroscopy. A comparison of Raman spectroscopic studies of mixed Na2SO4 and NaCl solutions with a constant SO42? concentration and variable Cl? concentrations suggest that the I1 parameter is affected by Cl?, whereas the I2 parameter was not. Therefore, even if the solution is not purely Na2SO4-H2O, SO42? concentrations can still be calculated from the Raman spectra if the H2O band is deconvoluted into two sub-bands, making this method potentially applicable to analysis of natural fluid inclusions.

Abstract:Previous cryogenic Raman spectroscopic analysis of H2O-NaCl-CaCl2 solutions has identified the Raman peaks of various hydrates of NaCl and CaCl2, and established a linear relationship between Raman band intensity of the hydrates and the composition of the solution (NaCl/(NaCl+CaCl2) molar ratio, or XNaCl) using synthetic fluids, which created the opportunity to quantitatively determine the solute composition of aqueous fluid inclusions with cryogenic Raman spectroscopy. This paper aims to test the feasibility of this newly established method with natural fluid inclusions. Twenty-five fluid inclusions in quartz from various occurrences which show a high degree of freezing during the cooling processes were carefully chosen for cryogenic Raman analysis. XNaCl was calculated using their spectra and an equation established in a previous study. These inclusions were then analyzed with the thermal decrepitation-SEM-EDS method. The XNaCl values estimated from the two methods show a 1:1 correlation, indicating that the new, non-destructive cryogenic Raman spectroscopic analysis method can indeed be used for fluid inclusion compositional study.

Abstract:The GOI (grains containing oil inclusions) index is used to distinguish oil zones, oil-water zones and water zones in sandstone oil reservoirs. However, this method cannot be directly applied to carbonate rocks that may not have clear granular textures. In this paper we propose the Effective Grid Containing Oil Inclusions (EGOI) method for carbonate reservoirs. A microscopic view under 10× ocular and 10× objective is divided into 10×10 grids, each with an area of 0.0625 mm×0.0625 mm. An effective grid is defined as one that is cut (touched) by a stylolite, a healed fracture, a vein, or a pore-filling material. EGOI is defined as the number of effective grids containing oil inclusions divided by the total number of effective grids multiplied by 100%. Based on data from the Tarim Basin, the EGOI values indicative of the paleo-oil zones, oil-water zones, and water zones are >5%, 1%–5%, and <1%, respectively. However, the oil zones in young reservoirs (charged in the Himalayan) generally have lower EGOI values, typically 3%–5%.

Abstract:Three-phase NaCl-H2O fluid inclusions featuring halite dissolution temperature (Tm) higher than vapor bubble disappearance temperature (Th) are commonly observed in porphyry copper/molybdenum deposits, skarn-type deposits and other magmatic - hydrothermal ore deposits. Based on │ΔVl│ (the absolute value of volume variation of NaCl-H2O solution in a heating or cooling process of inclusions)=│ΔVs│ (the absolute value of volume variation of the halite crystal in a heating or cooling process of inclusions) and on the principle of conservation of the mass of NaCl and H2O, we systematically calculated the densities of NaCl-H2O solutions in the solid-liquid two-phase field for temperatures (Th) from 0.1°C to 800°C and salinities from 26.3 wt% to 99.2wt%. Consequently for the first time we obtained the upper limit of the density of NaCl-H2O solutions in the solid-liquid two-phase field for Th

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Abstract:Uranium, as one of twenty–six kinds of important minerals in China, is strategic resource and energy mineral, which has been thoroughly investigated in the project of National Potential Evaluation of Uranium Resource. During the implementation of this project, the authors summarized the metallogenic regularity of uranium resource in China systematically, through the researches of geological characteristics of uranium resource, uranium deposits type (genetic and prediction type), temporal and spatial distribution, and metallogenic series. Based on the investigation of present situation and progress in uranium exploration, this paper proposes the uranium deposits in China should be divided into 4 classes, 9 types, 21 subtypes in genetic, and 50 types in prediction; suggests to divide China into 29 uranium metallogenic belts and 20 uranium prospective area, and constructs 20 uranium–polymetallic metallogenic series, through summarizing temporal and spatial distribution characteristics and metallogenic regularity of uranium deposits in China. The above research is beneficial to the comprehensive understanding of regional uranium metallogenic regularity, and will direct the uranium exploration in the future.

Abstract:The new century has witnessed a strategic breakthrough in unconventional oil & gas. Hydrocarbon accumulated in micro-/nano-scale pore throat shale systems has become an important domain that could replace current oil & gas resources. Unconventional oil & gas plays an increasingly important role in our energy demand. Tight gas, CBM, heavy oil and asphaltic sand have served as a key domain of exploration & development, with tight oil becoming a ‘bright spot’ domain and shale gas becoming a ‘hotspot’ domain. China has made great breakthroughs in unconventional oil & gas resources, such as tight gas, shale gas, tight oil and CBM, and great progress in oil shale, gas hydrate, heavy oil and oil sand. China has an estimated (223–263)×108 t of unconventional oil resources and (890-1260)×1012 m3 of gas resources. China has made a breakthrough for progress in unconventional oil & gas study. New progress achieved in fine-grained sedimentary studies related to continental open lacustrine basin large-scale shallow-water delta sand bodies, lacustrine basin central sandy clastic flow sediments and marine-continental fine-grained sediments provide a theoretical basis for the formation and distribution of basin central reservoir bodies. Great breakthroughs have been made in unconventional reservoir geology in respect of research methodology & technology, multi-scale data merging and physical simulation of formation conditions. Overall characterization of unconventional reservoirs via multi-method and multi-scale becomes increasingly popular and facilitates the rapid development of unconventional oil & gas geological theory, method and technology. The formation of innovative, continuous hydrocarbon accumulation theory, the establishment of the framework of the unconventional oil & gas geological theory system, and the determination of the implications, geological feature, formation mechanism, distribution rule and core technology of unconventional oil & gas geological study lays a theoretical foundation for extensive unconventional oil & gas exploration and development. Theories and technologies of unconventional oil & gas exploration and development developed rapidly, including some key evaluation techniques such as ‘sweet spot zone’ integrated evaluation and a six-property evaluation technique that uses hydrocarbon source, lithology, physical property, brittleness, hydrocarbon potential and stress anisotropy, and some key development & engineering technologies including micro-seismic monitoring, horizontal drilling & completion and “factory-like” operation pattern, “man-made reservoir” development, which have facilitated the innovative development of unconventional oil & gas. These breakthroughs define a new understanding in four aspects: ①theoretical innovation; ② key technologies; ③ complete market mechanism and national policy support; and ④ well-developed ground infrastructure, which are significant for prolonging the life cycle of petroleum industry, accelerating the upgrade and development of theories and technologies and altering the global traditional energy structure.

Abstract:Molybdenum is one of the dominant minerals in China because of its rich reserves. In recent years, outstanding breakthroughs have been made in molybdenum prospecting in China, and the distribution of molybdenum deposits in China is found to have a “planar pattern”. In general, the molybdenum deposits are concentrated in eastern China, including the largest molybdenum reserves of Henan Province. In terms of the scale of molybdenum deposits, the identified resources of the superlarge deposits are the most important, which account for about 53% of the whole country, and those of the large deposits account for about 30%, those of the medium-sized deposits account for about 14%, those of the small-sized deposits, mine spots and mineralization account for about 3%. The molybdenum deposits are mainly classified as porphyry type, skarn type, hydrothermal (vein) type and sedimentary (metamorphic) type in genesis, and the identified resources of these types account for 85.75%, 8.83%, 2.79% and 2.63% of the total resources respectively. Based on the statistics of precise chronology data of molybdenites Re-Os, Mo-mineralization can be divided into 6 periods in Chinese geological history, which are Precambrian (>800 Ma), Cambrian-Silurian (540-415 Ma, Caledonian), Devonian-Permian (400-290 Ma, Hecynian), Triassic (260-200 Ma, Indosinian), Jurassic-Cretaceous (195-70 Ma, Yanshanian) and Paleogene-Neogene (65-10 Ma, Himalayan). Mo mineralization during the Yanshanian period is the strongest one, in which about 76.69% of the Chinese total identified resources was formed. The second is the Himalayan period. According to spatial-temporal distribution characteristics of molybdenum deposits, the metallogenic regularity of molybdenum deposits was preliminarily summarized, and 41 level-III molybdenum-forming belts, 13 level-II molybdenum-forming provinces and 4 level-I molybdenum-forming domains were ascertained in the mainland of China. There are 39 metallogenic series of and 60 sub-series of molybdenum deposits with molybdenum as the dominant metal and corresponding representative molybdenum deposits proposed. Metallogenic lineages of molybdenum deposits were also established. Spatial-temporal evolution of different types of molybdenum deposits, and the relationship between Mo-mineralization and tectonic evolution have been discussed in this paper. On this basis, the authors think that element Mo is an effective tracer for recording the crustal evolution history of China. At present, there are some problems in the exploration of Mo deposits in China, such as uneven exploration degrees in eastern and western China, shallow exploration depth, low and uneven grade, complex associated components, difficulty of mineral development and utilization, increasing costs of prospecting, and so on. According to successful experience of superficial and deep prospecting and considering also the discussion above, some suggestions are proposed for the prospecting of molybdenum deposits in the future.

Abstract:China has widely distributed silver deposits, and is rich in silver resources. Although silver deposits are mainly associated with Pb-Zn deposits, a number of independent silver deposits have also been discovered in recent years. Silver deposits include different types, such as submarine volcanism and continental volcanism related type, intrusion related type, and sedimentary related type. This study summarized the metallogenic regularity of China’s silver deposits systematically based mainly on the data from 490 silver deposits. It is shown that submarine volcanic sedimentary type, continental volcanic or sub-volcanic type, skarn type, hydrothermal type (including vein type and stratabound type), sedimentary metamorphic type, sedimentary type and regolith type should be regarded as the most important prediction types of silver deposit. A total of 32 silver mineralization belts and 111 silver concentration areas have been delineated. The map of "Spatial distribution of silver mineralization belts in China" and other series of maps finished in this study may provide a theoretical basis for the evaluation and prognosis of silver resources potential in China.

Abstract:China is rich in tin resources, and contains many types of tin deposits. Among the tin deposit types, the cassiterite-sulfide type, skarn type and quartz vein type occupy a large proportion of tin resources and reserves. From the aspect of exploitation and utilization, the most important types are cassiterite-sulfide type and quartz vein type. The cassiterite-sulfide type tin deposits are mainly located in Northern Guangxi and Eastern Yunnan, skarn type deposits are mainly distributed in the ore-concentration areas of South Hunan in Middle Nanling, and the quartz vein type tin deposits are mainly distributed in South China, such as Western Fujian, Middle Jiangxi, Northern Guangzhou and Southern Hunan. The most important metallogenic epoch for tin deposits is the Mesozoic era. The metallogenic geotectonic background is mainly continental environments after orogeny process, with strong tectonic changes, interlaced deep fracture and frequent magmatism. And the most distinctive feature is the well developed Mesozoic granites, which have a close relationship with tin mineralization. Based on the detailed study of the data from 873 tin deposits in China, this paper summarized the metallogenic regularity of tin deposits, classified 20 important metallogenic series of tin or tin-associated deposits, and inferred that the cassiterite-sulfide type, skarn type, quartz vein type and greisen type are the main prediction types of tin resources. Forty-four tin-mineralization belts were divided, among which, 19 belts are the most important. In addition, a series of maps about tin metallogenic belts and tin metallogenic regularity were compiled, aiming to provide theoretical basis for potential estimation and prediction of tin mineral resources.

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