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Different from the Qaidam basin with about 320 billion m3 microbial gas, only limited microbial gases were found from the Junggar basin with similarly abundant type III kerogen. To determine whether microbial gases have not yet identified, natural gas samples from the Carboniferous to Cretaceous in the Junggar basin have been analyzed for chemical and stable isotope compositions. The results reveal some of the gases from the Mahu sag, Zhongguai, Luliang and Wu-Xia areas in the basin may have mixed with microbial gas leading to straight ethane to butane trends with a "dogleg" light methane in the Chung's plot. Primary microbial gas from degradation of immature sedimentary organic matter is found to occur in the Mahu sag and secondary microbial gas from biodegradation of oils and propane occurred in the Zhongguai, Luliang and Beisantai areas where the associated oils were biodegraded to produce calcites with δ13C values from + 22.10‰ to + 22.16‰ or propane was biodegraded leading to its 13C enrichment. Microbial CH4 in the Mahu sag is most likely to have migrated up from the Lower Wuerhe Formation coal-bearing strata by the end of the Triassic, and secondary microbial gas in Zhongguai and Beisantan uplifts may have generated after the reservoirs were uplifted during the period of the Middle and Late Jurassic. This study suggests widespread distribution of microbial gas and shows the potential to find large microbial gas accumulation in the basin. [ABSTRACT FROM AUTHOR]

The strongly 13C-depleted calcite in the Doushantuo cap dolostones (∼635 Ma) of South China is considered to form via thermochemical or biological oxidation of methane by sulfate in an environment with sulfate concentrations close to that of modern seawater (∼28 mM). Here we demonstrate that the coeval seawater sulfate levels were indeed low (∼1 to 3 mM) because all bulk δ34S values of pyrites are close to and higher than the coeval seawater, with only a few showing a wide in situ δ34S range from 5 to 62‰. Such low sulfate concentrations were initially consumed by sulfate reducing microorganisms to extremely low levels (<∼0.2 mM), and thus Mn-driven anaerobic oxidation of methane (AOM) by sulfate occurred in pore water to produce H 2 S, which was in turn oxidized by Mn oxides back to sulfate. Consequently, with increasing Mn reduction and decreasing sulfate concentrations in pore waters, the produced pyrite shows an increase of in situ δ34S values, and is in association with calcite with more negative δ13C values, and an inherited positive Ce anomaly from Mn oxides. Finally, the pyrite with the highest δ34S value may have co-precipitated with the 13C-depelted calcite (with a nadir of −58‰), and thus show similarly high Mn concentrations (∼20000 μg/g). This is the first report of sulfate-dependent AOM driven by Mn- or Fe- oxides from the entire Precambrian record. Such a previously unrecognized biogeochemical cycling during Marinoan global deglaciation may serve as the mechanism for major methane sink during the Proterozoic and Archean with low sulfate concentrations in the oceans. [ABSTRACT FROM AUTHOR]

Diamondoid compounds are widely used to reflect thermal maturation of high mature source rocks or oils and oil cracking extents. However, diamondoids and thiadiamondoids were demonstrated to have newly been generated and decomposed in our hydrothermal pyrolysis of crude oil and TSR experiments. Our results show that adamantanes and diamantanes are generated primarily within the maturity range 0.48–2.1% and 1.2–3.0% EasyRo, respectively. Their formation is enhanced and the decomposition of diamantanes obviously lags at elevated temperatures compared with anhydrous experiments. MDI, EAI, DMAI-1, DMDI-2 may serve as reliable maturity proxies at > ca.1.0% EasyRo, and other isomerization indices (TMAI-1, TMAI-2 and DMAI-2) are effective for the highly mature organic matter at EasyRo > 2.0%. The extent of oil cracking (EOC) calculated from the broadly used (3- + 4-) MD method (Dahl et al. in Nature 399:54–56, 1999) is proven to overestimate, especially for highly cracked samples due to the new generation of (3- + 4-) MD. Still, it can be corrected using a new formula at < 3.0% EasyRo. Other diamondoid-related indices (e.g., EAI, DMDI-2, As/Ds, MAs/MDs, DMAs/DMDs, and DMAs/MDs) can also be used to estimate EOC. However, these indices cannot be applied to TSR-altered petroleum. TSR is experimentally confirmed to generate diamantanes and thiaadmantanes at 1.81% EasyRo likely via direct reactions of reduced S species with hydrocarbons and accelerate the decomposition of diamantanes at > 2.62% EasyRo compared with thermal chemical alteration (TCA). More studies are needed to assess specific mechanisms for the formation of thiadiamondoids under natural conditions. [ABSTRACT FROM AUTHOR]

It is not well understood how, in the immediate aftermath of the Sturtian Snowball Earth, marine sulfur cycling resulted in a global distribution of sedimentary pyrite with δ34S values higher than coeval seawater. Here, we analyze the quadruple sulfur isotope systematics of organic-bound sulfur (OS) from the lowermost post-Sturtian Datangpo Formation, South China, and identify two generations of OS formation, each sampling an isotopically distinct sulfate reservoir (δ34S ≈ 26‰ and 52–93‰) that differentially impacted its respective, co-occurring pyrite. Combining several lines of geochemical evidence, we argue that the first OS generation was the product of a sulfate-impoverished meltwater-influenced setting, with OS preservation being the result of resistance to acid hydrolysis. However, the second OS generation was sourced from H 2 S produced in sediments during early diagenesis via microbial reduction of a 34S-enriched sulfate pool derived from overlying euxinic or ferruginous seawater. This is the first ancient marine data set where all observed pyrite is more enriched in 34S than its associated OS. Our proposed origin may be applied to global superheavy pyrite (SHP) immediately after the Sturtian and is comparable to processes linked to freshwater-to-marine transitions during rising sea level in the wake of recent glaciation. [ABSTRACT FROM AUTHOR]

Diamondoid compounds are widely used to reflect thermal maturation of high mature source rocks or oils and oil cracking extents. However, diamondoids and thiadiamondoids were demonstrated to have newly been generated and decomposed in our hydrothermal pyrolysis of crude oil and TSR experiments. Our results show that adamantanes and diamantanes are generated primarily within the maturity range 0.48–2.1% and 1.2–3.0% EasyRo, respectively. Their formation is enhanced and the decomposition of diamantanes obviously lags at elevated temperatures compared with anhydrous experiments. MDI, EAI, DMAI-1, DMDI-2 may serve as reliable maturity proxies at > ca.1.0% EasyRo, and other isomerization indices (TMAI-1, TMAI-2 and DMAI-2) are effective for the highly mature organic matter at EasyRo > 2.0%. The extent of oil cracking (EOC) calculated from the broadly used (3- + 4-) MD method (Dahl et al. in Nature 399:54–56, 1999) is proven to overestimate, especially for highly cracked samples due to the new generation of (3- + 4-) MD. Still, it can be corrected using a new formula at < 3.0% EasyRo. Other diamondoid-related indices (e.g., EAI, DMDI-2, As/Ds, MAs/MDs, DMAs/DMDs, and DMAs/MDs) can also be used to estimate EOC. However, these indices cannot be applied to TSR-altered petroleum. TSR is experimentally confirmed to generate diamantanes and thiaadmantanes at 1.81% EasyRo likely via direct reactions of reduced S species with hydrocarbons and accelerate the decomposition of diamantanes at > 2.62% EasyRo compared with thermal chemical alteration (TCA). More studies are needed to assess specific mechanisms for the formation of thiadiamondoids under natural conditions. [ABSTRACT FROM AUTHOR]

This study aimed to reveal the impact of excessive dietary fibre (DF) intake on inflammatory responses and bile acid (BA) homeostasis in largemouth bass (Micropterus salmoides) and the potential mechanism. In vitro BA binding capacity was compared, and the results showed that the BA binding capacity to chenodeoxycholic acid and glycocholic acid by pectin and soybean meal was higher than cellulose and cottonseed meal respectively. An in vivo trial was conducted using a diet without DF as a control (CON diet), while test diets contained 150 g/kg cellulose (CEL diet) or pectin (PEC diet), 500 g/kg soybean meal (SBM diet) or cottonseed meal (CSM diet). Fish were overfed and ate ad libitum. Compared to fish fed the CON diet, fish fed the PEC and SBM diets showed high expression of inflammatory factor genes and BA synthesis factor genes and obvious histopathological damage in the gut and liver, while the responses of fish fed the CEL and CSM diets were mild. Whole‐body BA contents in fish fed all test diets were lower than those in fish fed the CON diet (p < 0.05). These results support the hypothesis that excessive DF intake induces inflammatory responses and dysregulation of BA homeostasis, which might be attributed to their binding capacity to BAs. [ABSTRACT FROM AUTHOR]

The extent of atmospheric and oceanic oxygenation during the Mesoproterozoic remains an area of active debate. Here, we report major and trace elements, organic sulfur (OS) speciation, sulfur isotopes in multiple phases [pyrite (py), OS, and carbonate-associated sulfate (CAS)], and a numerical model of sulfate concentrations from one of the Mesoproterozoic's best-preserved geochemical archives, the Xiamaling Formation (ca. 1.4 Ga) in the Yanliao Basin. These data reveal a previously unrecognized ocean-atmosphere oxygenation process. Starting with Unit 3, intense sulfurization increased organic carbon burial and thus oxygen release, resulting in a deep-water oxidation event within the Yanliao Basin that could be regarded as a transient restricted oxygen oasis based on low pyrite content, elevated kerogen S:C ratios, higher δ34S py than δ34S OS (Δδ34S OS-py < 0), and a low calculated sulfate concentration of ∼0.07–0.14 mM. During Unit 2, the basin was reconnected to the open ocean with the deposition of organic-rich shale across northern China and northern Australia, accompanied by a shift in Δδ34S OS-py to 5.0‰ and a calculated seawater sulfate concentration of ∼0.1–1.14 mM. Such large-scale burial of organic matter released oxygen into the atmosphere, accompanied by significant sulfate delivery to the basin and euxinic conditions characterized by Mo concentrations and 34S-depleted pyrite at the topmost of Unit 2. A subsequent globally synchronized atmospheric and deep ocean oxygenation event may have occurred during Unit 1. This event was recorded by a progressive increase in Δδ34S OS-py (up to +9.6‰), increased oxidized OS species, and positive Ce anomalies (attributed to the reductive dissolution of the Ce-enriched Mn oxides), all of which were caused by increased sulfate concentrations (calculated to be ∼1.15–2.31 mM) and a spatial descent of the redox interface. The combination of these lines of evidence illustrates the sensitivity of the oceanic sulfur cycle to the ocean-atmosphere system and provides novel constraints on oxygenation at ∼1.4 Ga. • Oxygenation processes from local to global at ∼1.4 Ga are indicated by the difference between organic and inorganic δ34S. • A restricted supply of reactive iron is likely to facilitate the sulfurization of organic matter. • Local oxygenation might be triggered by sulfurization-induced organic matter burial and subsequent oxygen release. • Atmospheric oxygenation will increase the weathering input of oxidants causing the oxygenation event in the deep ocean. [ABSTRACT FROM AUTHOR]

Neoproterozoic marine dolomite cements represent reliable, albeit complex, archives of their palaeoenvironment. Petrological and high‐resolution geochemical data from well‐preserved fibrous dolomite and pyrite in the upper Ediacaran (ca 551·1 to 548·0 Ma) Dengying Formation in south‐west China are presented and discussed here. The aim of this research is to reconstruct the redox state of late Ediacaran shallow seawater and porewater in the Sichuan Basin using early marine diagenetic fabrics. Based on crystalline texture and axis, four basic types of fibrous dolomite cements formed penecontemporaneously in a microbialite reef setting at the platform margin: (i) bladed dolomites (replacement from a high‐Mg calcite precursor); (ii) fascicular fast dolomites (replacement from an aragonitic precursor); (iii) fascicular slow dolomites; and (iv) radial slow dolomites. The latter two fabrics are considered direct marine porewater precipitates due to their length‐slow character, cathodoluminescent zonation, and enriched copper and cobalt concentrations. Marine cements yield rare earth element and yttrium patterns comparable to modern seawater and represent a refined set of archive data relative to previously published bulk dolostones. Redox‐sensitive elements and cathodoluminescence indicate that the fascicular fast dolomites formed in suboxic seawater, while fascicular slow and radial slow dolomites formed in euxinic marine porewaters. Microbial sulphate reduction during the formation of fascicular slow and radial slow dolomites is recognized by nanometre‐scale spheroidal ankerite and sulphur‐containing dolomite, and intergrown pyrite grains with U‐shaped δ34S transects. Data shown here suggest predominantly suboxic shallow late Ediacaran seawater and euxinic marine porewaters, with microbial activity promoting the direct precipitation of dolomite. [ABSTRACT FROM AUTHOR]

Pr and Ph are preferentially oxidized compared to n C 17 and n C 18 , leading to decrease in Pr/ n C 17 and Ph/ n C 18 ratios with thiaadamantanes concentrations, a measure of the extent of TSR in Tazhong oils and condensates. • TSR does not preferentially deplete triterpanes and α,β hopanes over Ts. • Pr and Ph are preferentially oxidized over n C 17 and n C 18. • i C 4 was preferentially depleted over n C 4 only during earlier TSR stage. • Relative oxidization sequence during TSR overlaps significantly. Tazhong and four other well-known TSR-altered petroleum reservoirs from around the world were analyzed for their molecular and carbon isotopic compositions of saturated hydrocarbons, thiaadamantanes concentrations or H 2 S contents to determine the relative stability of saturated hydrocarbons during thermochemical sulfate reduction (TSR). We find that TSR does not preferentially deplete tricyclic terpanes and 17α, 21β hopanes with the "exposed" tertiary carbon atoms compared to 18α (H)-22, 29, 30-trisnorhopane (Ts) and C 29 Ts that have no tertiary carbon atoms, as proposed by Xia and Gong [35]. However, pristane (Pr) and phytane (Ph) seem to have been preferentially oxidized over normal C 17 and C 18 alkanes, respectively, resulting in decreasing Pr/ n C 17 and Ph/ n C 18 ratios with increasing extent of TSR for the Tazhong and Nisku oils and condensates. i C 4 appears to be preferentially depleted relative to n C 4 during early TSR stage. At later TSR stage both n C 3 and n C 4 are oxidized more readily than i C 4 in the Mobile Bay Norphlet Formation condensates. Thus, we tentatively propose that relative oxidization order during TSR may start with long chain iso -alkanes followed by n -alkanes, then cycloalkanes, C 2 -C 4 alkanes and finally methane; however, it seems that oxidization of these compounds overlaps significantly. [ABSTRACT FROM AUTHOR]

Marinoan cap carbonates are the first sedimentary rocks deposited after the Marinoan Snowball Earth glaciation and likely record the marine geochemical signals across the Cryogenian-Ediacaran boundary. The nature of the parent fluids, the possible precursor mineralogies and the dolomitisation models of these carbonates are debated to the present day. Cap carbonates and their fibrous dolomite cement samples from the Jiulongwan and Huajipo sections in South China were analysed for their petrography and geochemistry. Data obtained shed light on the deposition and alteration history of cap carbonates. Two types of fibrous dolomite cement precipitated penecontemporaneously with platform carbonate sediment deposition: (i) isopachous fascicular-optic dolomite fabrics with a characteristic botryoidal habit and mottled cathodoluminescence colour; they likely formed via an aragonitic precursor; and (ii) radial-slow dolomite cement, representing a direct marine precipitate. Growth zones are recognised under the SEM and visible in alternating dull- and bright-red zones under the cathodoluminescence microscope. Basal cap carbonates (Ce anomalies: 0.85 ± 0.11; Mn: 3324.3 ± 558.2 ppm) and the base (Ce anomalies: 0.83 ± 0.22; Mn: 2349.2 ± 1276.4 ppm) of fascicular-optic dolomite cement from platform facies indicate anoxic marine seawater with high Mn concentrations. Based on the geochemical data of fibrous dolomite and blocky calcite cement, the marine porewater evolved from the Mn reduction zone (Ce anomalies: 1.04 ± 0.26) to the sulphate reduction zone (Ce anomalies: 1.00 ± 0.48) and the Fe reduction zone (Ce anomaly: 1.40). In situ trace and rare earth elemental contents and the transition from a dull to bright fluorescence colour along the fibrous dolomite transects point to the former activity of microbial sulphate reduction and the degradation of organic matter. These two factors likely facilitated the formation of cap dolostone and multiphase dolomite cement crusts in a marine seawater (porewater) environment. Data shown here are significant for those concerned with the palaeoenvironmental archive and the dolomitisation process of Marinoan cap dolostones. Cartoon and a summary of petrographic and geochemical properties from cap carbonate substratum to fibrous dolomite cement and blocky calcite cement. Red rectangle shown in stratigraphic context is enlarged as the phase section. [Display omitted] • Fascicular-optic dolomite has an aragonitic precursor, radial-slow dolomite represents marine precipitate. • Depositional seawater is anoxic with high Mn contents. • Microbial sulphate reduction and the degradation of organic matter facilitated dolomitisation. [ABSTRACT FROM AUTHOR]

The peritrophic membrane (PM) is located in the gut of most insects and protects them from invasion by pathogens or toxins ingested during feeding. Peritrophins are a principal component of the PM and contribute to the structure and function of the PM. The PM has also been observed in the gastrointestinal tract of the Chinese mitten crab (Eriocheir sinensis). In this study, full‐length cDNA sequences of two PM genes from E. sinensis were obtained, namely, Es‐peritrophin1 and Es‐peritrophin2, which were 855 bp and 1,611 bp respectively. The deduced proteins were composed of 267 and 468 amino acids and contained 3 and 1 chitin binding domains respectively. Both Es‐peritrophin1 and Es‐peritrophin2 contained a signal peptide sequence at the N terminus, indicating that both proteins were secretory proteins. Phylogenetic analysis revealed that Es‐peritrophin1 and Es‐peritrophin2 were divided into the CPAP3‐B and CPAP1‐H branches respectively. Nevertheless, sequence alignment demonstrated that they had lower homology to other known PMs, indicating they were two novel peritrophins. Quantitative real‐time PCR (qRT‐PCR) analysis showed that both the Es‐peritrophin1 and Es‐peritrophin2 transcript levels were high in the stomach and hindgut and lower in the midgut, indicating that the PM might be assembled locally in E. sinensis. The expression of Es‐peritrophin1 and Es‐peritrophin2 was downregulated by high‐pH stress and Aeromonas hydrophila challenge in the examined tissues except in the hindgut, where the expression of both genes was upregulated by A. hydrophila challenge. These results indicated that Es‐peritrophin1 and Es‐peritrophin2 are two novel peritrophin genes related to immune defence in E. sinensis. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The sandstone-hosted Qianjiadian uranium deposit, hosted in the Upper Cretaceous Yaojia Formation in the Qianjiadian area, Songliao Basin, NE China, has been studied for over twenty years. However, there exists debate on whether mineralization fluid is low-temperature groundwater in favor of biogenic mineralization or diabase-related magmatic hydrothermal fluid for this deposit and other adjacent geologically linked sandstone-hosted uranium deposits (Baixingtu, Baolongshan and Huitianzhao deposits) in the North China. This study provided new data from petrographic and geochemical analyses, geochronology of uranium minerals (the EMPA chemical dating method) and petroleum hydrocarbon biomarkers in host sandstones. Two types of host sandstone were recognized. In calcareous sandstones, pitchblende coexists with colloform pyrite and poikilitic calcite cement while quartz and feldspars were extensively corroded. In non-calcareous sandstones, coffinite coexists with colloform pyrite and only feldspars were slightly corroded. This suggests that pitchblende formed in high pH (pH > ∼9) fluid, while the pH of ore-forming fluid for coffinite was lower (pH = 7–9). Besides, EMPA chemical dating revealed two stages of uranium mineralization. Stage-A occurred in 43–28 Ma with pitchblende as the only uranium mineral species. Stage-B occurred in 19–3 Ma with the formation of both pitchblende and coffinite. The uranium mineralization was biogenic under low-temperature groundwater condition and thus not from a diabase-related mafic magmatic hydrothermal fluid based on the following lines of evidence: (i) some coffinite occurs as phosphorus-rich microorganism-like microspherules structure; (ii) pyrite aggregates were generated from bacterial sulfate reduction as indicated by the δ34S values as low as −41.4‰; (iii) calcite cement in calcareous sandstone contains only single phase aqueous inclusions, and have δ13C values as low as −11.2‰, indicating that part of the carbon was derived from organic matter oxidation; (iv) the organic matter oxidation is further supported by hydrocarbons extracted from petroleum inclusions within calcite cement, showing occurrence of C 26 –C 31 17α, 21β 25-norhopanes, typically resulting from heavy biodegradation. [ABSTRACT FROM AUTHOR]

The effects of plant protein sources (PPSs) on the health of the liver and intestine of the largemouth bass, Micropterus salmoides, were compared to verify the potential damaging effects of dietary fiber (DF). A diet containing 55% fish meal (FM) was used as the control. The test diets contained 25% soybean meal (SBM), rapeseed meal (RSM), cottonseed meal, or peanut meal, and the FM content was decreased to 30%. The protein and lipid contents of these five diets were balanced by casein and oil. Fish were raised for 8 weeks. The fish fed the diet containing PPS showed a trend of decreasing growth and apparent digestibility coefficients. The contents of total bile acid, lipid, and collagen in the liver were increased, and the mRNA expression levels of genes encoding inflammatory factors and enzymes involved in de novo fatty acid synthesis and bile acid synthesis were upregulated. Both the lipid and collagen contents in the liver were positively correlated with the DF content in the diet significantly. Morphology and histology showed reduced liver size, hepatic steatosis, and fibrosis in fish fed diets containing PPS. The lowest hepatosomatic index was observed in fish fed the SBM diet, and the most severe damage was observed in fish fed the RSM diet. No obvious histological abnormalities were observed in the hindgut. The bile acid profile in the liver could be used to distinguish the types of PPS very well by Fisher discriminant analysis. These results indicated that 25% of each of the four PPSs in the diet exceeded the tolerance range of largemouth bass and caused liver damage, which might be mediated by bile acid. DF in PPS might be an important agent contributing to liver damage. [ABSTRACT FROM AUTHOR]

Ultrasound is recognized as a non-conventional processing technology for food preservation and quality improvement. Effects of thermal and ultrasound treatment on the inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in bayberry juice were studied. Whether cooling with ice bath during ultrasound treatment was conducted to separate effects of heat and cavitation effects. In all processes, the inactivation kinetics of PPO and POD followed a first-order model (R 2 = 0.864–0.997).The D T value during thermal inactivation varied from 151.99 to 6.23 min for PPO and the corresponding Z T values and activation energy (E a ) were 13.16 °C and 166.77 kJ/mol, while those parameters of POD were 298.26–7.08 min, 14.25 °C and 153.49 kJ/mol, respectively. The ultrasound (US) inactivation rate constants (k) for PPO ranged from 0.0556 min − 1 to 0.8878 min − 1 with the corresponding D values of 41.44–2.59 min and Z UI values of 312.50 W/cm 2 . However, the k value of PPO during ultrasound with cooling (USC) decreased to 0.0412–0.3268 min − 1 , while the D and Z UI values increased to 55.92–7.05 min and 432.90 W/cm 2 , indicating that the heat brought out during ultrasound treatment significantly enhanced the inactivation kinetics of PPO. The inactivation rates of POD by US treatment were also higher than those by USC at the same ultrasound intensity and time. In addition, the kinetic parameters for POD by US and USC treatment were lower than those of PPO, inferring its more sonication resistant. Industrial relevance Ultrasound is a non-thermal food processing method for microorganism and enzyme inactivation, as well as quality maintenance. Attractive color is one of the most important quality attribute of bayberry products and strongly affects the consumer acceptance and preference. A key role in color degradation in berry fruit products is attributed to enzymatic browning of phenolic compounds which mainly related to PPO and POD. Therefore, the inactivation of PPO and POD is necessary for better color retention and shelf life increasing. This study would provide technical support for PPO and POD inactivation of ultrasound technique in bayberry juices processing. [ABSTRACT FROM AUTHOR]

Reservoir solid bitumens from the Permian to Triassic and potential source rocks in the northeastern Sichuan Basin were measured for elemental and stable carbon (δ 13 C) and sulfur (δ 34 S) isotopic compositions to determine the chemical and isotopic composition of non-TSR and TSR-altered solid bitumen and to develop proxies to reflect the extent of bitumen alteration by TSR. Non-TSR altered reservoir bitumen samples showed S/C atomic ratios ⩽0.03 and had δ 13 C values closer to Longtan Formation (P 3 l) kerogen than to the Lower Silurian and Cambrian kerogens, and δ 34 S values slightly more enriched than P 3 l kerogens. The TSR-altered solid bitumens have incorporated significant amounts of TSR-derived H 2 S resulting in S/C atomic ratios (0.047–0.074) and δ 34 S values (13.4–24.0‰) being significantly higher than those of the solid bitumen not altered by TSR (S/C: 0.013–0.030; δ 34 S: 5.8–9.6‰) and the potential source rock kerogen. The incorporation has produced a decrease in N/C ratio and negative shift of −2.7‰ in δ 13 C values that resulted from increasing TSR-H 2 S back reactions with 12 C-rich n -alkanes from the gas phase, soluble solid bitumen or paleo-oil to generate organic sulfur compounds such as ethanethiol that were incorporated into the solid bitumens, which is followed by further aromatization and polymerization. The solid bitumens show positive relationships of S/C ratios and δ 34 S values to the associated gas H 2 S/(H 2 S + ΣC 1–6 ) or TSR extents, and thus the S/C ratios and δ 34 S values can be used as proxies to reflect TSR extents. [ABSTRACT FROM AUTHOR]

Chemistry, H, O and Sr isotopes of formation waters were determined from the Ordovician carbonate reservoirs in the Tazhong area, Tarim basin. The aim is to elucidate their origin and migration and their alteration by thermochemical sulfate reduction (TSR) and water-rock interactions. The waters were originated from evaporated seawater, and are enriched in Ca and Sr, and depleted in Mg and SO 4 compared with the seawater evaporation trajectory (SET), thus are considered to result from dolomitization, anhydrite dissolution and in situ TSR. δ 18 O values show positive shift due to water-rock interactions, and δD values show negative shift with increasing TSR extents or total thiaadamantanes concentrations of the associated oils, likely resulting from hydrogen isotope exchange with TSR-H 2 S. However, the δD-δ 18 O relationship was mainly controlled by the mixing with paleo-meteoric water with δD of −50‰ and δ 18 O of −7.5‰. Paleo-meteoric water may have leached the Silurian siliciclastic rocks and thus has 87 Sr/ 86 Sr up to 0.715. Upper Ordovician (O 3 l) formation water shows more negative δD and δ 18 O values, higher 87 Sr / 86 Sr ratios and lower total dissolved solids (TDS) than the O 1–2 y water, which may have resulted from mixing of paleo-meteoric water. Lower Ordovician (O 1–2 y) formation water shows 87 Sr / 86 Sr ratio of 0.7095–0.7105, TDS from 160 to 240 g/l, and Sr concentrations from 300 to 1000 mg/L, which may have resulted from mixing with hydrothermal fluid up-migrated from Ediacaran and Lower Cambrian siliciclastic rocks. Significant mixings with paleo-meteoric water and hydrothermal fluid occurred at paleo-highland at the east of No.1 Fault-Slope Zone and active faulting zone near No.10 Structural Belt, respectively. Hydrothermal fluid and oils probably shared similar migration pathways in No.10 Structural Belt. Formation water geochemistry may thus provide clues to constraint on petroleum migration. [ABSTRACT FROM AUTHOR]

Petroleum stability varies greatly among different basins with light oil recently being produced from reservoirs at depths up to 8260 m and present bottom hole temperatures up to 171 °C in the Tarim Basin. Determining the extent of oil-gas conversion (EOGC) and its controls are crucial to the "exploration deadline" of temperature or depth for liquid hydrocarbons. For this purpose, about 90 oils from the Cambrian and Ordovician in the Tarim Basin have been analyzed for biomarkers, diamondoids and thiadiamondoids, and their gas/oil ratios were collated. These oils have EOGC from 45.4 to 98.3% for TSR-altered oils in the Tazhong and Shunbei areas, and only 0–49.2% for all other non-TSR oils. Among non-TSR-altered oils, Tazhong oils show higher EOGC values (28.0–49.2%) than those in Tabei (0–9.7%) and Shunbei (0–32.7%) oils, respectively. We propose that higher heating rates (7 °C/Ma) and shorter durations (<5 Ma) at high temperatures (>150 °C) may account for the lower EOGC values of oils in the Tabei and Shunbei areas than those in the Tazhong with values of 0.1 °C/Ma and 250 Ma (>120 °C), respectively. The oil may be completely converted to methane-dominated gas if it was exposed to high temperatures for a longer duration as exampled from gas pools from the Lower Cambrian in the Sichuan Basin. In this case, the oil was heated at a rate of 1 °C/Ma since the oil charge and experienced >200 °C for about 50 Ma. Thermochemical sulfate reduction may have enhanced the conversion of oil to gas, leading to an increase in EOGC values from 30% for non-TSR-altered oils to 98% for the strongly TSR-altered oil in the eastern Tazhong area with similar burial-heating history. A similar case for elevated EOGC due to TSR can be found in the Smackover Formation, Gulf of Mexico. Thus, two global models related to heating rate and duration at high temperatures and TSR are developed to illustrate oil stability with temperature and are expected to be instructive for deep petroleum exploration. • The extents of oil-gas conversion in the Tarim Basin vary widely in different areas. • Higher heating rates and shorter durations at high temperatures may favor the preservation of oil. • TSR could lower oil and gas stability and accelerate the conversion of oil to wet gas and of wet gas to dry gas. • Two global models are developed to illustrate oil stability with temperature. [ABSTRACT FROM AUTHOR]

Deeply buried (4500–7000 m) Ordovician carbonate reservoirs in the Tazhong area, Tarim Basin, NW China show obvious heterogeneity with porosity from null in limestones and sweet dolostones to 27.8% in sour dolostones, from which economically important oils, sour gas and condensates are currently being produced. Petrographic features, C, O, Sr isotopes were determined, and fluid inclusions were analyzed on diagenetic calcite, dolomite and barite from Ordovician reservoirs to understand controls on the porosity distribution. Ordovician carbonate reservoirs in the Tazhong area are controlled mainly by initial sedimentary environments and eo-genetic and near-surface diagenetic processes. However, vugs and pores generated from eogenetic and telogenetic meteoric dissolution were observed to have partially been destroyed due to subsequent compaction, filling and cementation. In some locations or wells (especially ZG5-ZG7 Oilfield nearby ZG5 Fault), burial diagenesis (e.g. thermochemical sulfate reduction, TSR) probably played an important role in quality improvement towards high-quality reservoirs. C2 calcite and dolomite cements and barite have fluid inclusions homogenization temperatures (Ths) from 86 to 113 °C, from 96 to 128 °C and from 128 to 151 °C, respectively. We observed petrographically corroded edges of these high-temperature minerals with oil inclusions, indicating the dissolution must have occurred under deep-burial conditions. The occurrence of TSR within Ordovician carbonate reservoirs is supported by C3 calcite replacement of barite, and the association of sulfur species including pyrite, anhydrite or barite and elemental sulfur with hydrocarbon and 12 C-rich (as low as −7.2‰ V-PDB) C3 calcite with elevated Ths (135–153 °C). The TSR may have induced burial dissolution of dolomite and thus probably improved porosity of the sour dolostones reservoirs at least in some locations. In contrast, no significant burial dissolution occurred in limestone reservoirs and non-TSR dolostone reservoirs. The deeply buried sour dolostone reservoirs may therefore be potential exploration targets in Tarim Basin or elsewhere in the world. [ABSTRACT FROM AUTHOR]

Cambrian dolostone reservoirs in the Tarim Basin, China, have significant potential for future discoveries of petroleum, although exploration and production planning is hampered by limited understanding of the occurrence and distribution of dolomite in such ancient rocks buried to nearly 8 km. The study herein accessed new drill core samples which provide an opportunity to understand the dolomitization process in deep basins and its impact on Cambrian carbonate reservoirs. This study documents the origin of the dolostone reservoirs using a combination of petrology, fluid-inclusion microthermometry, and stable and radiogenic-isotopes of outcrop and core samples. An initial microbial dolomitization event occurred in restricted lagoon environments and is characterized by depleted δ13C values. Dolomicrite from lagoonal and sabkha facies, some fabric-retentive dolomite and fabric-obliterative dolomite in the peloidal shoal and reef facies show the highest δ18O values. These dolomites represent relatively early reflux dolomitization. The local occurrence of K-feldspar in dolomicrite indicates that some radiogenic strontium was contributed via terrigenous input. Most fabric-retentive dolomite may have precipitated from seawater at slightly elevated temperatures, suggested by petrological and isotopic data. Most fabric-obliterative dolomite, and medium to coarse dolomite cement, formed between 90°C and 130°C from marine evaporitic brine. Saddle dolomite formed by hydrothermal dolomitization at temperatures up to 170°C, and involved the mixing of connate brines with Sr- enriched hydrothermal fluids. Intercrystalline, moldic, and breccia porosities are due to the early stages of dolomitization. Macroscopic, intergranular, vuggy, fracture and dissolution porosity are due to burial-related dissolution and regional hydrothermal events. This work has shown that old (for example, Cambrian or even Precambrian) sucrosic dolomite with associated anhydrite, buried to as much as 8000 m, can still have a high potential for hosting substantial hydrocarbon resources and should be globally targeted for future exploration. [ABSTRACT FROM AUTHOR]

We attempted to differentiate the effects of thermal chemical alteration (TCA) from thermochemical sulfate reduction (TSR) on formation and isomeric distribution of thiadiamondoids and diamondoids in oils and condensate from deeply buried Cambrian and Ordovician carbonate reservoirs in the Tarim Basin, China. Diamondoids and thiadiamondoids with 1–3 cages were detected in all the oils analyzed. Total thiadiamondoid concentrations reflect extent of TSR. Diamondoid concentrations and most of the diamondoid-based maturity proxies and the source rock lithology proxy increase with increasing extent of TSR, indicating that they are controlled by the extent of the TSR process (or reaction with H 2 S) to a greater degree than by TCA. TSR may have oxidized hydrocarbons to oxygenated species and finally to CO 2 and newly generated and concentrated diamondoids and organic sulfur compounds. The most extensive TSR-altered ZS1C condensate contains 3.2 wt% total dibenzothiophenes, 0.4 wt% thiadiamondoids and 5.9 wt% diamondoids together with higher polymantanes including tetramantanes and pentamantanes in association with polythiadiamondoids, including dithiaadamantanes, trithiaadamantanes and tetrathiaadamantanes. These polythiadiamondoids have been detected only from heavily TSR-altered petroleum in this study and North American samples and may be derived from the sulfurization of hydrocarbons, including diamondoids, under high temperature and highly reducing conditions during advanced stages of TSR. The polymantanes may have been generated from alkylation of lower-cage diamondoids and subsequent homologation, or from free radical reactions. This study indicates that TSR may have led to the generation and isomerization of thiadiamondoids and diamondoids, and thus diamondoid-based maturity and lithology proxies cannot be used to reflect maturity and lithology in the TSR active areas, and that the occurrence of polythiadiamondoids can be used to indicate heavy TSR alteration. [ABSTRACT FROM AUTHOR]

Fibrous carbonate cement is a common phase in marine phreatic environments — but its origin and diagenetic history are underexplored. This paper compares two fibrous fabrics that are different in terms of their peculiarities but share important similarities regarding their essentials: upper Ediacaran fibrous dolomite cement and Upper Ordovician fibrous calcite cement, both from the Tarim Basin, China. The focus is on the significance of these fabrics as archives of their marine paleoenvironment. Upper Ediacaran fibrous dolomite cement is present as (i) a fascicular-optic and (ii) a radial-fibrous phase. Judging from the optical length-slow character and luminescent zones, radial-fibrous dolomite cement precipitated directly from early diagenetic marine porewater. Fascicular-optic dolomite cement has a length fast optical character and hence likely formed as a high-Mg calcite precursor penecontemporaneously in a reefal, shallow-marine diagenetic environment. Similarly, two types of Upper Ordovician fibrous cement are present: (i) radiaxial-fibrous and (ii) fascicular-optic calcite cement. Fascicular-optic calcite precipitated in a marine phreatic platform environment, whereas radiaxial-fibrous calcite cement formed in an early marine diagenetic porewater environment. Both fabrics arguably replace a magnesium calcite precursor. For the case of the Tarim Basin, cathodoluminescence and redox-sensitive elements indicate predominantly anoxic, upper Ediacaran marine waters (Ce anomaly = 0.8 ± 0.2), and suboxic, Upper Ordovician shallow-marine seawater (0.7 ± 0.2). Based on PHREEQC modeling, the shallow burial, upper Ediacaran porewater (5.1) yields a higher dolomite saturation index than upper Ediacaran (4.8) and Upper Ordovician seawater (3.7). The direct precipitation of radial-fibrous dolomite from Ediacaran porewaters was likely induced due to organic matter decomposition and related seawater oxygen depletion, elevated Mg2+/Ca2+ ratios, and high alkalinity values. Modeling and proxy data show significant hydrogeochemical differences between seawater and porewater in the upper meters of the sediment column. The upper Ediacaran seawater apparently favored fibrous cement formation with magnesium calcite precursors. In contrast, fibrous dolomite cement was directly precipitated in an early-diagenetic marine porewater regime. The comparability of proxy data reflecting seawater and such recording early diagenetic marine porewater is critically discussed. The Ediacaran early diagenetic marine porewater yields higher dolomite saturation index than the Ediacaran seawater and Ordovician seawater. [Display omitted] • Radial-fibrous dolomite with length-slow character and well-preserved zone is primary. • Fascicular-optic calcite and radiaxial-fibrous calcite have precursor of Mg-calcite. • Aqueous chemistry shows variation from shallow seawater to early diagenetic porewater. • Anoxic, elevated Mg2+/Ca2+ ratios and alkalinity favored the precipitation of dolomite. [ABSTRACT FROM AUTHOR]

Thermochemical sulfate reduction (TSR) is a set of redox reactions between organic matter and sulfates at temperatures >120 °C, and occurs in varied environments including deeply buried carbonate and clastic rocks, Mississippi Valley- and Sedimentary Exhalative type metal deposits, and early oceans on Earth and likely on Mars. TSR may be methane-, and heavy hydrocarbons-dominated ones, and is most likely initiated by H 2 S with labile organosulfur compounds (OSCs) as an intermediate product to generate CO 2 and organic non‑sulfur and sulfur compounds. Of the organic non‑sulfur containing compounds, dealkylated- and carboxylated- polycyclic aromatics are formed due to oxidation, and 1- to 6- cage diamandoids are generated under highly reducing environments. Sulfur in thermally stable dibenzothiophenes and thiadiamondoids of a TSR oil represents cumulative or mixed sulfur from source kerogen decomposition and newly generated sulfur from different TSR stages, whilst sulfur from thiolanes is simultaneously generated from or exchanges isotopically with H 2 S newly generated during TSR. Thermochemical reduction of dissolved sulfate by organic matter produces significant sulfur isotope fractionation, resulting in extremely heavy residual sulfates and wide ranges of produced sulfide δ34S values in some metal deposits and likely on Mars. In contrast, no significant fractionation occurs in the majority of petroleum reservoirs due to anhydrite dissolution as a rate-limited step. On Mars the presence of kerogen, methane, sulfates, sulfides, OSCs, chlorobenzene and likely sulfonic acids and active magmatic-hydrothermal activities indicates a potential of ongoing and past TSR. Methane-dominated TSR may generate water and carbonates with oxygen contributed from sulfate, and both are in oxygen isotope equilibration. In contrast, no water is formed by TSR of oils and condensates and carbonates newly precipitated are not in oxygen isotope equilibration with formation water. • TSR may have been auto-catalyzed by labile sulfur compounds (LSCs) not by S 3 −. • S-isotope fractionation occurs in hydrothermal deposits and likely on Mars not in petroleum reservoirs. • Both de-alkylation and alkylation occur during TSR generating O- and S-bearing compounds. • Only methane- and ethane-dominated TSR generates water with oxygen contributed from sulfate. • Mango K1 can be used as a proxy to indicate TSR extents. [ABSTRACT FROM AUTHOR]

• Two stages of hydrothermal events account for carbonate-hosted mineralization. • Quartz precipitated from silica-rich fluids from the Precambrian sandstone layers. • Saddle dolomite, fluorite and calcite formed in the Cambrian shale-derived fluids. • The same parent fluid could precipitate different minerals in differing host rocks. • Basal sandstones do not always act as lateral conduits for hydrothermal fluids. Contrasting mineral assemblages have been frequently found in Neoproterozoic-lower Paleozoic carbonate reservoirs along high-angle faults in the Tarim Basin. However, the reason for the change in mineral types over time is poorly constrained. Field and petrographic observations, fluid inclusion microthermometry, rare earth element (REE) and C, O and Sr isotope analyses are used to constrain the changes in water chemistry and fluid flow during the development of the mineral assemblages. During the Middle Devonian-early Carboniferous, the flux of hydrothermal fluids from Neoproterozoic sandstone layers, linked to the activity of NE–SW-trending strike-slip faults, resulted in extensive silicification. The silica-bearing fluids were hot (128.1–209.4 °C), saline (17.1–21 wt% NaCl eq.) and enriched in radiogenic strontium and showed no link to large-scale petroleum migration. During the Permian, a regional thermal anomaly induced the expulsion of hydrocarbon-bearing hydrothermal fluids from lower Cambrian shales, where Mg2+, 87Sr and F− were derived via the transformation and leaching of clay minerals. A more significant in situ source of Mg2+ was the dolostone interval, as the migrating fluids contributed to the precipitation of saddle dolomite with high T h values (82–176.4 °C) and salinities (15–21.4 wt% NaCl eq.), negative δ18O values and radiogenic Sr compositions. The succession of saddle dolomite followed by fluorite with similar T h values, salinities and 87Sr/86Sr ratios indicates a Mg2+ deficit and increased dissolved calcium activity in the same parent fluid system, which facilitated the breakdown of MgF− and combination of Ca2+ and F−. Subsequently, cooling and desalination of the hydrothermal fluids occurred, which was induced by the infiltration and mixing of meteoric water related to the compression and uplift of the north-western flank of the Tarim block. These processes resulted in the precipitation of milky white calcite (Cal 1) with similar oxygen and strontium isotope compositions but wider ranges of T h (82.1–154 °C) and salinity (3.4–16.9 wt% NaCl eq.) than those of the saddle dolomite and fluorite. The lateral flow of hydrothermal fluids through suitable layers, such as bed interfaces, permeable aquifers and karstic units, facilitated the formation of stratabound mineral deposits away from the feeding faults. The termination of hydrothermal mineralization was marked by the precipitation of brown calcite (Cal 2), whose meteoric origin has been proven by the combination of its reddish staining, oscillatory luminescent zonation and low δ18O values. This integrated study approach improves the understanding of the diversity of exotic mineral assemblages in carbonate hosts and the evolution and migration of hydrothermal fluids connected to late Paleozoic tectonism. [ABSTRACT FROM AUTHOR]

During thermochemical sulfate reduction (TSR), H 2 S generated by reactions between hydrocarbons and aqueous sulfate back-reacts with remaining oil-phase compounds forming new organosulfur compounds (OSCs) that have similar δ 34 S values to the original sulfate. Using Compound Specific Sulfur Isotope Analysis (CSSIA) of alkylthiaadamantanes (TAs), alkyldibenzothiophenes (DBTs), alkylbenzothiophenes (BTs) and alkylthiolanes (TLs), we have here attempted to differentiate OSCs due to primary generation and those due to TSR in oils from the Tarim Basin, China. These oils were generated from Cambrian source rocks and accumulated in Cambrian and Ordovician reservoirs. Based on compound specific sulfur isotope and carbon isotope data, TAs concentrations and DBT/phenanthrene ratios, the oils fall into four groups, reflecting different extents of source rock signal, alteration by TSR, mixing events, and secondary generation of H 2 S. Thermally stable TAs, that were produced following TSR, rapidly dominate kerogen-derived TAs at low to moderate degrees of TSR. Less thermally stable TLs and BTs were created as soon as TSR commenced, rapidly adopted TSR-δ 34 S values, but they do not survive at high concentrations unless TSR is advanced and ongoing. The presence of TLs and BTs shows that TSR is still active. Secondary DBTs were produced in significant amounts, sufficient to dominate kerogen-derived DBTs, only when TSR was at an advanced extent. The difference in sulfur isotopes between (i) TLs and DBTs and (ii) BTs and DBTs and (iii) TAs and DBTs, represents the extent of TSR while the presence of TAs at greater than 20 μg/g represents the occurrence of TSR. The output of this study shows that compound specific sulfur isotopes of different organosulfur compounds, with different thermal stabilities and formation pathways, not only differentiate between oils of TSR and non-TSR origin, but can also reveal information about relative timing of secondary charge events and migration pathways. [ABSTRACT FROM AUTHOR]

Well-exposed Lijiatuo Section was chosen to explore the temporal evolution and controls of the oceanic redox state, primary productivity and seawater sulfate levels during the Cambrian Series 1-2, South China. This section consists of Xiaoyanxi Formation (Fm.) mudstones and Liuchapo Fm. cherts that deposited in the slope and basin environment. Five oxic-anoxic cycles were identified based on V/Sc, Th/U and the enrichment factors of Mo, U, V, Ni and Cu. The Middle-Upper Liuchapo Fm. and the Middle Xiaoyanxi Fm. were deposited under oxic-suboxic conditions, and the rest of the strata were under anoxic conditions. The Re/Mo ratio demonstrated that the oxic-suboxic conditions in the Middle Xiaoyanxi Fm. were accompanied by transient sulfidic conditions, and the rest of the section was underanoxic and non-sulfidic conditions. All the TOC and the enrichment factors of Ba, Ni, Cu, Zn and Cd demonstrated that both the sinking and burial flux of organic matter (OM) in Liuchapo Fm. were lower than that in the overlying Xiaoyanxi Fm. The highest sinking and burial flux of OM in the Xiaoyanxi Fm. appeared at its lower parts; however, the lowest sinking and burial flux of OM in the Xiaoyanxi Fm. appeared in its middle parts. TOC/TS, TS and the vertical trend of δSpy demonstrated that the seawater was dominated by low oceanic sulfate levels, which resulted in the absence of free HS. The rise of the atmospheric oxygen content may be the principal driver for the associated, transient suboxic-oxic and nearly sulfidic environment in the middle Xiaoyanxi Fm. [ABSTRACT FROM AUTHOR]

The impact of burial diagenesis (especially deep burial-related processes such as thermochemical sulfate reduction, TSR) on the distribution of rare earth elements and yttrium (REY) in diagenetic minerals in carbonate reservoir has gained little attention even though they may be unique indicators of the diagenetic system being closed or open to external influx of material. Trace element and REY concentrations, 87 Sr/ 86 Sr, δ 18 O and δ 13 C have been determined for limestone, host dolomite, pore-filling calcite (calcite-2), and late stage fracture-filling calcite (calcite-3), barite (barite-2) and anhydrite (anhydrite-3) from Lower Triassic Feixianguan Formation reservoirs in northeast Sichuan Basin, China. Calcite-2, calcite-3, barite-2, and anhydrite-3 precipitated during deep burial (from 110 °C to 220 °C), demonstrated by petrology and fluid inclusion thermometry. Sr isotope analysis revealed that diagenetic carbonate minerals and anhydrite have largely identical 87 Sr/ 86 Sr ratios to Triassic seawater, indicating negligible input of Sr from terrigenous sources and probably a relatively closed diagenetic environment for precipitation of these minerals. Carbon isotope analysis showed that calcite-2 has relatively low δ 13 C values (down to − 18.9‰ V-PDB), suggesting that they are TSR calcites with the carbonate derived from oxidized, isotopically-light hydrocarbons. Unlike the seawater-like REY patterns of the limestone and dolomites, calcite-3 and anhydrite-3 are enriched in rare earth elements (ΣREE) and show light rare earth element enrichment and heavy rare earth element depletion, exhibiting a chevron-like pattern of shale normalized REY trends. In contrast, TSR calcite (calcite-2) has similar ΣREE to the host dolomite but a relatively flat REY SN pattern, suggesting strong variations in elemental and REE compositions of the burial fluids. Significantly, TSR calcite shows a prominent positive Eu anomaly and an unusually high-chondritic Y/Ho ratio. Both yttrium versus holmium fractionation and Eu 2 + oxidation to Eu 3 + must have occurred during thermochemical sulfate reduction. Hence, a positive Eu anomaly and an elevated Y/Ho ratio may be used as effective proxies to differentiate calcite resulting from TSR from ordinary calcite cement. This is especially useful when carbon isotope analysis cannot be used to give an unambiguous interpretation of the origin of the calcite. [ABSTRACT FROM AUTHOR]

Gases, oils, solid bitumen samples and fluid inclusions were analyzed for chemical composition and δ 13 C and δ 34 S values, and production data were collated, to elucidate the origin and fates of the H 2 S in the Tazhong area. The H 2 S in the Ordovician was measured to have δ 34 S values from 12.1‰ to 23.4‰, which are significantly lighter than the counterpart in the Cambrian (33.0‰), indicating that the H 2 S did not migrate from the Cambrian, but may have been derived from thermochemical sulfate reduction in situ , as partially supported by 12 C-rich CO 2 in fluid inclusions and TSR calcites with δ 13 C values from −3.6‰ to −17.7‰ in the Ordovician. The H 2 S rich gas subsequently mixed with H 2 S-poor, 13 C rich methane-dominated gas as indicated by the roughly negative correlations of H 2 S content to dryness and gas/oil ratio, and CH 4 from fluid inclusions having δ 13 C values 1.2–3.6‰ lighter than the associated free gas. The H 2 S has been dissolved in formation water, precipitated as pyrite and incorporated into oils and solid bitumens, resulting in the generation of alkylthiolanes, alkylthiols and alkyl 2-thiaadamantanes, and increase in δ 34 S values and S/C ratios of the solid bitumen. The content of H 2 S produced from the water intervals or petroleum–water transition zones is significantly contributed from exsolved gas and thus higher than that of the gas-cap gas in the reservoirs. Thus, H 2 S contents cannot be used to indicate TSR extents in the Ordovician. However, in the Cambrian, whole oil and saturates show positive shifts in δ 13 C values with increasing H 2 S contents, indicating that the H 2 S in the Cambrian was derived from TSR by liquid hydrocarbons. [ABSTRACT FROM AUTHOR]

Deep burial carbonate reservoirs (>4000 m) have great potential of reserves for oil and gas exploration, although the matrix reservoirs generally become extremely heterogeneous and tight due to various diagenesis. Hydrothermal dissolution is supposed to be important for formation of high-quality deep burial carbonate reservoirs. However, few studies have focused on influence of minor fluorine-bearing fluid on carbonate reservoir quality. This study integrates petrography, geochemistry and fluid inclusion data to understand impact of fluorine-bearing fluid on deep burial carbonate reservoirs. Mineralogy and mineral distribution suggest that fluorite and concomitant calcite are found in the Ordovician and Cambrian strata of the whole Tazhong area, especially in the vicinity of faults. Calcite associated with fluorite is probably derived from progressive mixture between formation water and fluorine-bearing hydrothermal fluid, which is supported by REY pattern of concomitant calcite, surrounding limestone and fluorite, and fluid inclusion microthermometric data of concomitant calcite and fluorite. Fluorine-bearing hydrothermal fluid was responsible for the concomitant C2 calcite of high Y/Ho ratio. Therefore, the superchondritic Y/Ho ratio of concomitant calcite can be probably used as proxy for identifying distribution of minor fluorine-bearing hydrothermal fluid. For thick fluorite bed, influx of fluorite-rich fluid resulted in surrounding limestone dissolution and altered zones between fluorite and limestone. This process simultaneously improves porosity and permeability of high-energy sedimentary facies reservoirs. In contrast, the fluorine-rich hydrothermal fluid through the low-energy sedimentary facies mainly enhanced permeability of the tight carbonate reservoirs rather than porosity. For widespread tight reservoir of high-energy and low-energy sedimentary facies, even minor fluorite-bearing fluids still enhance permeability. The fluorine-bearing hydrothermal fluid may influence carbonate reservoirs away from hydrothermal-altered zones. Significance of minor fluorine-bearing hydrothermal fluid for widespread tight carbonates has probably been underestimated for deep burial carbonate reservoir. • Calcite associated with fluorite is derived from mixture between formation water and fluorine-bearing hydrothermal fluid. • Superchondritic Y/Ho ratio of calcite can be probably used as proxy for distribution of fluorine-bearing hydrothermal fluid. • The ability of fluorine-rich fluid to improve carbonate reservoir quality is influenced by lithology and sedimentary facies. • Minor fluorine-bearing hydrothermal fluid can still improve permeability of deep burial tight carbonate reservoir. [ABSTRACT FROM AUTHOR]

Up until now, it has been assumed that oil in the Palaeozoic reservoirs of the Tazhong Uplift was derived from Upper Ordovician source rocks. Oils recently produced from the Middle and Lower Cambrian in wells ZS1 and ZS5 provide clues concerning the source rocks of the oils in the Tazhong Uplift, Tarim Basin, China. For this study, molecular composition, bulk and individual n -alkane δ 13 C and individual alkyl-dibenzothiophene δ 34 S values were determined for the potential source rocks and for oils from Cambrian and Ordovician reservoirs to determine the sources of the oils and to address whether δ 13 C and δ 34 S values can be used effectively for oil–source rock correlation purposes. The ZS1 and ZS5 Cambrian oils, and six other oils from Ordovician reservoirs, were not significantly altered by TSR. The ZS1 oils and most of the other oils, have a “V” shape in the distribution of C 27 –C 29 steranes, bulk and individual n -alkane δ 13 C values predominantly between −31‰ to −35‰ VPDB, and bulk and individual alkyldibenzothiophene δ 34 S values between 15‰ to 23‰ VCDT. These characteristics are similar to those for some Cambrian source rocks with kerogen δ 13 C values between −34.1‰ and −35.3‰ and δ 34 S values between 10.4‰ and 21.6‰. The oil produced from the Lower Ordovician in well YM2 has similar features to the ZS1 Cambrian oils. These new lines of evidence indicate that most of the oils in the Tazhong Uplift, contrary to previous interpretations, were probably derived from the Cambrian source rocks, and not from the Upper Ordovician. Conversely, the δ 13 C and δ 34 S values of ZS1C Cambrian oils have been shown to shift to more positive values due to thermochemical sulfate reduction (TSR). Thus, δ 13 C and δ 34 S values can be used as effective tools to demonstrate oil–source rock correlation, but only because there has been little or no TSR in this part of the section. [ABSTRACT FROM AUTHOR]

Intense thermochemical sulfate reduction (TSR) and up to 18% H 2 S are found in the Upper Permian Changxing Formation (P 3 ch) in the northeast (NE) Sichuan Basin, China, despite that rare gypsum or anhydrite was found in this formation. Here, we present new concentration data of carbonate-associated sulfate (CAS) from carbonate host rocks, C, O, and Sr isotope data for TSR-related calcites, and S isotope data for sulfur compounds obtained during this study. These data along with spatial-temporal changes in palaeogeopressure conditions, hydraulic conductivity and the physical capacity indicate that the H 2 S was generated locally from TSR within the P 3 ch reservoirs. We propose that the reactive sulfates were derived from CAS released during dolomitization and recrystallization of earlier dolomite within the P 3 ch Fm. and from the cross-formational migration of evaporative brines from the Lower Triassic Feixianguan Formation (T 1 f) to P 3 ch Fm. Our calculation shows that the two sources could provide enough SO 4 2− for the generation of H 2 S within the P 3 ch reservoirs. Early downward migration of sulfate-rich evaporative brines from the T 1 f formation occurred in near-surface and shallow burial diagenetic settings (mainly <1000 m). The evaporative brines seeped into porous grainstones and displaced preexisting seawater, causing pervasive dolomitization within the P 3 ch Fm. Subsequently, TSR calcites precipitated from the pore water have high Sr concentrations (up to 7767 ppm), close to the T 1 f TSR calcites, and 87 Sr/ 86 Sr ratios mainly from 0.7074 to 0.7078, which are significantly higher than those of Late Permian seawater but within the range of early Triassic seawater. [ABSTRACT FROM AUTHOR]

Cherts of the Piyuancun Formation and black mudstones of the Hetang Formation in Diben Town, Kaihua County, Zhejiang were deposited in a deep water basin of the Lower Yangtze area during the Ediacaran-Cambrian transition (E-C transition), offering an opportunity to reconstruct the ancient redox condition of the deep water basin. Total 53 samples were collected and analyzed for iron speciation, including pyrite iron (FePy), carbonate associated iron (FeCarb), iron oxide and hydroxide (FeOx), magnetite iron (FeMag) and total iron (FeT) as well as δC to gain a deeper understanding of specific redox condition during the period. The results show that (1) most samples have pyrite concentration <1 %, with the FePy/FeHR ratio ranging from <0.01 to 0.81 (mostly <0.5), and the FeHR/FeT ratio between 0.39 and 0.93 (mostly >0.5). (2) The E-C boundary in the Diben section occurred at the maximum negative excursion of organic carbon isotope within the Piyuancun Formation, which can be correlated with other sections by using δC. We thus concluded that the relatively high content of highly reactive iron and low content of pyrite iron in the Diben section indicate a minor occurrence of HS and a predominance of anoxic and ferruginous environment, which is similar to other reported sections such as the Longbizui and Yanwutan sections, western Hunan. In addition, oxygen concentration in sea water showed an increasing trend in the interval corresponding to the bottom and upper layer of the Hetang Formation as indicated by the FeHR/FeT ratio, which decreased from 0.7 to 0.38, however, it was not great enough to oxidize the whole deep water. Therefore, during the E-C transition deep water basin in South China was most likely an anoxic and ferruginous enrironment, which prevented metazoon from the evolution in the deep water basin. Our work offers an important reference to better understanding of the spatiotemporal occurrence and dynamic processes of the 'Cambrian Explosion'. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of including high levels of oilseed meals in the diets of Chinese mitten crabs ( Eriocheir sinensis ) on their growth performance, non-specific immunity, hepatopancreatic function and intestinal morphology. Eight isonitrogenous and isoenergetic diets containing soybean meal (SBM), cottonseed meal (CSM), rapeseed meal (RSM) and peanut meal (PNM) were formulated. The control diet contained 400 g/kg fish meal (FM) and 150 g/kg combined oilseed meals. The content of each oilseed meal in test diets ranged from 400 or 600 g/kg diet, with the total oilseed meals in each test diet ranging from 760 to 840 g/kg. One diet containing 651 g/kg of the combined oilseed meals and 80 g/kg FM (diet FM80) was also assessed. The experimental diets were each fed to four replicate groups of juvenile crabs (1.48 ± 0.04 g) for 14 weeks. Results showed no differences in the survival rate and feed intake among the treatments (P>0.05). The specific growth rates (SGR) of the crabs fed the test diets were lower (P<0.05) than that of the control group, with the exception of crabs fed the FM80 diet, and those fed diets containing 400 g/kg CSM or PNM. The sum of essential amino acids, protein chemical score, essential amino acid index, and total oilseed meal content in the diet were correlated (P<0.05) with the SGR, protein efficiency ratio, and feed conversion ratio (feed:gain) which suggest that the diets containing high levels of oilseed meals may be deficient in certain amino acids. The total hemocyte count decreased (P<0.05) when the crabs were fed diets containing 400 g/kg RSM and 600 g/kg of any of the oilseed meals except CSM. Alanine aminotransferase activity increased (P<0.05) when crabs were fed diets containing 600 g/kg RSM or PNM. There were no differences (P>0.05) in the activities of serum lysozyme, superoxide dismutase, phenoloxidase, and aspartate aminotransferase among the treatments. Morphological analysis revealed the presence of a peritrophic membrane in the crab intestine and no obvious changes in the intestinal morphology were induced by the high levels of oilseed meals. The results suggest that higher levels of CSM or PNM, but lower amounts of SBM or RSM, could be included in the diets of the animals crabs. [ABSTRACT FROM AUTHOR]

Natural gases in Ordovician reservoirs of the Tazhong area of the Tarim Basin appear derived by oil-cracking gas. The gases show very different geochemical characteristics. Most of the gases in the middle and eastern part of the No. 1 fault-slope zone are characterized by high gas dryness coefficients and have methane δ 13 C 1 values heavier than primary gas. These features are different from gases in the western part of the No. 1 fault-slope zone. Thus, we propose that there existed mixing between more mature, 13 C-rich methane dominated gas and less mature wet gas with 13 C-depleted methane. The hypothesis is supported by (1) roughly a positive correlation between the gas dryness coefficient and methane δ 13 C 1 value, (2) significantly heavier δ 13 C 1 values in the eastern part of the study area than in the west, and (3) significantly heavier δ 13 C 1 values than anticipated for unaltered gas co-generated with C 2 –C 4 . The charge and mixing of the dry gas into the Ordovician pools may have resulted in increase in wax contents of the oils, gas/oil ratios, gas dryness coefficients and methane δ 13 C values, leading to a positive correlation between gas/oil ratio and paraffin wax content as a result of continuous fractionation and removal of light components of an oil with progressive gas influx and thus gas washing. [ABSTRACT FROM AUTHOR]

Abstract: Petrographic features, carbon and oxygen isotopes, and trace elements were determined, and fluid inclusions were analyzed on late diagenetic cements and vug-fillings from the Lower Triassic carbonates to account for much higher porosities in the sour dolomite reservoirs than in the sweet limestones in northeastern Sichuan Basin. In the NE side to the Kaijiang-Liangping Trough, dolostone reservoirs have porosities mainly from 6 to 12%, up to 28% and contain 9–20% H2S. The dolomite includes pre-bitumen re-crystallized silt-sized crystals without occurrence of fluid inclusions, and late burial dolomite. The late burial dolomite has been measured to have fluid inclusions homogenization temperatures (HTs) from 72 to 128 °C. Part of the dolomites with HTs up to 121 °C show corroded edges or replacement by TSR calcites. TSR calcites show δ 13C values from −2.3 to −18.9‰, FeO from null to 810 μg/g and SO3 from 50 to 18,700 μg/g. Vug-filling TSR calcites have much lower FeO and SO3 than the replacement calcites of anhydrite, suggesting that dissolved Fe2+ released from the dissolution of dolomite and anhydrite as a result of TSR may have reacted with TSR-H2S and precipitated as pyrite. The dissolution may have released 13C-rich CO2 resulting in the present-day CO2 having δ 13C values significantly heavier than those of the TSR calcites as light as −18.9‰. The dolomite and anhydrite dissolution during late stage of TSR may have enlarged or redistributed porosity in the NE side dolostones. In contrast, oolitic limestone reservoirs in the SW side contain significantly lower sulfates and thus no significant late-diagenetic dissolution and TSR. The porosity difference in the two sides resulted from original physical property due to early dolomitization and subsequent improvement from anhydrite and dolomite dissolution as a result of TSR. [Copyright &y& Elsevier]

Sulfur isotopic variation has been widely used to study the environmental backdrop of the end-Permian mass extinction (EPME), although research to date has focused mostly on carbonate-associated sulfate (CAS) and pyrite. Study of the δ34S of kerogen, as well as of its H- and C-isotopic compositions, is relatively rare, although such data have the potential to shed new light on our understanding of the proximate driver of the EPME event. Here, we report paired δ34S pyrite and δ34S kerogen values for three widely spaced end-Permian marine sections from South China (Meishan, Shangsi, and Guanzi) that represent a transect from upper-slope (shallow-water) to basinal (deep-water) facies, as well as additional data for Meishan (i.e., δ34S CAS , δ2H kerogen, and δ13C kerogen). Our results show that oxidation of isotopically light H 2 S in upwelled anoxic watermasses led to negative shifts of δ34S CAS , δ34S kerogen and δ34S pyrite in the ocean-surface layer during the Late Permian, and an increase of Δ34S CAS-kerogen in the upper-slope Meishan section. High Δ34S kerogen-pyrite (>10‰) in the Meishan section indicates that slow pyritization occurred considerably below the sediment-water interface. In contrast, the lower-slope Shangsi and deep-water Guanzi sections show more negative δ34S values for both kerogen and pyrite, with smaller Δ34S kerogen-pyrite (mainly 5–10‰), implying open-system microbial sulfate reduction (MSR) in an anoxic deep watermass. A large negative shift in δ2H kerogen from the uppermost Permian to the lowermost Triassic is most plausibly attributed to increased sedimentation rates and organic matter inputs due to collapse of terrestrial ecosystems. High sedimentation rates may have been contributed to observed subsequent increase of (poly)sulfide δ34S within the Lower Triassic in shallow-water facies. Our study thus demonstrates the utility of integrated analysis of S-isotopes in pyrite, kerogen, and CAS, coupled with H- and C-isotopic data of kerogen for tracking dynamic environmental changes during the Permian-Triassic transition and possibly other major events in Earth history. [ABSTRACT FROM AUTHOR]

Abstract: Thermochemical sulfate reduction is considered to result in H2S >10% and high dryness coefficient values in the Lower Triassic and Upper Permian carbonate reservoirs in the NE Sichuan Basin. The gases produced from gas–water transition and water intervals were measured to have H2S higher than 30%, and are calculated to have significantly higher H2S and CO2 contents than a gas produced from a gas interval, and thus are not used to reflect TSR extents. Methane and ethane were shown to shift positively in carbon isotopes as a result of TSR. However, the fractionation has not quantitatively described. A logarithmic relationship is found to give the best fit for methane δ13C1 and [1 − H2S/(∑C1–6+H2S)] for all the gases with an equation of δ13C1, t = −16.6lnx − 33.0, indicating a closed system Rayleigh distillation with a kinetic fractionation factor αC of 1.0166. Ethane shows similar δ13C2 shift to methane (6.1‰ vs 5.5‰) for H2S/[H2S + ∑C1–6] = 0.2 in the NE Sichuan Basin. The δ13C2 deviation is significantly less than that of Mobile Bay Jurassic Norphlet Fm TSR-altered ethane (+16‰) for H2S/[H2S + ∑C1–6] = 0.1 (Mankiewicz et al., 2009). The ethane in association with high H2S (>10%) in NE Sichuan Basin shows slightly lighter δ13C values than those of the potential source rocks. Thus, it is possible for small amounts of gas derived from cracking of the source rocks to have mixed with TSR-altered gas in the high H2S pools. [Copyright &y& Elsevier]

Abstract: Two experiments were conducted to evaluate the feasibility of including high levels of rapeseed meal (RSM) and peanut meal (PNM) in juvenile crucian carp (Carassius auratus gibelio♀× Cyprinus carpio♂) diets by investigating the growth performance, immunity, intestinal morphology, and microflora of these animals. Fish meal (FM)-based diets were used as controls in both experiments. In experiment 1, RSM and PNM replaced 250 (RSM25 and PNM25) and 500 (RSM50 and PNM50) gkg−1 of FM in test diets. In experiment 2, RSM and PNM substituted 500gkg−1 of FM in test diets (RSM50′ and PNM50′, respectively). The diets in experiment 2 were isonitrogenous and isocaloric, and supplemental crystalline amino acids were added to compensate for the reduction in essential amino acids. More than 100gkg−1 of FM was maintained in the test diets in both experiments to ensure palatability, and fish were fed these diets for 8weeks. No significant changes in feed intake were noticed among groups in both experiments. In experiment 1, the growth rate (GR) of fish fed test diets was significantly lower than in fish fed control diets; the feed conversion ratios (FCR) were higher in fish fed test diets than in fish fed control diets with the exception of fish fed the PNM25 diet. The lower GR observed in fish fed test diets was partly due to reduced dietary energy and protein levels. No significant differences were observed in the GR of fish in experiment 2; however, the FCR of fish fed the RSM50′ diet increased, whereas the protein efficiency ratio decreased in fish of both test groups, suggesting that growth retardation would have occurred over a longer period. No significant changes were observed in serum superoxide dismutase activity in both experiments. Compared with control groups, the lymphocyte proliferation index (LPI) decreased in fish fed the RSM50 diet but not in those fed the RSM50′ diet; the LPI increased in fish fed the PNM50 and PNM50′ diets. The secretion of mucus, which formed a peritrophic membrane-like structure, was enhanced when diets included high levels of RSM and PNM. Mild intestinal histological changes, but no significant inflammatory responses or intestinal microflora changes, were observed. From these results, we came to the general conclusion that the inclusion of high levels of RSM and PNM in the diet not only retarded growth but also produced health risks to the crucian carp. [Copyright &y& Elsevier]

It is hard to determine secondary microbial gas from deep burial reservoirs with multiple generations of petroleum charge. Herein, oils at depths from 5000 m to 6500 m in the Ordovician carbonate reservoirs, Tarim basin, are found to have been biodegraded to secondary microbial gas. These oils experienced severe biodegradation and thus contain abundant 25-norhopanes and 17-nortricyclic terpanes. The associated gases have methane δ13C 1 from −51.9‰ to −47.3‰ and δ2H 1 from −327.8‰ to −192.4‰, and CO 2 δ13C CO2 from −0.7‰ to +15.3‰. These features suggest that the gases are secondary microbial gas, generated predominantly via CO 2 reduction with preferential reduction of 13C-depleted CO 2 and contribution of methane hydrogen from formation water in closed environments. The secondary microbial gas may have generated from biodegradation of oils at reservoir temperatures of about <75°C during the Late Permian, and has subsequently mixed with a later charge of non-biodegraded oils and wet gas during the Late Cretaceous. Consequently, the present gas shows relatively low dryness (C 1 /∑C 1 – 4 < 0.87) and has varied δ13C 1 and δ2H 1 values in methane. The study implies that the signatures of secondary microbial gas can easily be masked by thermogenic gas and thus more secondary microbial gas has yet to be identified. [ABSTRACT FROM AUTHOR]

It is hard to distinguish pyrites generated by microbial sulfate reduction (MSR) from thermochemical sulfate reduction (TSR). The upper Ediacaran Dengying Formation (ca 551–541 Ma) of Sichuan basin is chosen to study for this purpose by means of petrological, bulk and micrometer-scale analyses on barite, pyrite, calcite, and dolomite for carbon and sulfur isotope and rare earth elements and yttrium (REY) compositions. We find that MSR-derived pyrites precipitated from near-surface to shallow burial settings are characterized by seawater-like REY patterns and superchondritic Y/Ho ratios (74.3 ± 9.5), and have δ34S pyrite values in a wide range from −36.8‰ to 34.8‰, positively correlated with arsenic contents, likely through cryptic sulfur cycles driven by arsenic. In contrast, TSR-derived pyrites generated during deep burial settings have REY characterized by non-seawater-like patterns and chondritic Y/Ho ratios (33.6 ± 5.1), and show small sulfur isotopic fractionations (~10.5‰). TSR-pyrites yield both U-shaped and bell-shaped δ34S transects compared with U-shaped distributions of MSR-pyrites. The calcites associated with the TSR-pyrites show LREE enrichment, elevated Y/Ho ratios (85.8 ± 14.2) and negative δ13C values, likely resulting from decomposition of organic matter. This study highlights a combination method from REY patterns, δ13C and δ34S values from analyses on micro-sized pyrite and the associated calcites can be used to effectively distinguish MSR from TSR. [Display omitted] • MSR-pyrites have different petrology, REY and δ34S patterns from TSR-pyrites. • Cryptic sulfur cycles are likely driven by redox-sensitive metals such as arsenic. • TSR-calcites show LREE enrichment, elevated Y/Ho ratios and negative δ13C values. [ABSTRACT FROM AUTHOR]

China is the world's largest producer of aquatic animals, and the Taihu Lake area is one of the most important contributors within China. To obtain the basic information needed to minimize environmental impacts of aquaculture, the water quality and volume of effluents from 48 ponds used for raising crab, shrimp, river prawn, black carp, grass carp and turtles near Taihu Lake were monitored, and their pollutant loads were estimated. Effluent volumes ranged from 12.7 ± 1.7 (crab) to 50.9 ± 15.8 (turtle) thousand tons ha−1 year−1. The concentration of pollutants in the effluents often exceeded acceptable limits for Taihu Lake. Crab ponds produced the lowest gross loads of total nitrogen, total phosphorus, chemical oxygen demand and total suspended solids, whereas turtle ponds produced the highest. The net loads of monitored pollutants comprised only 4-53% of the gross loads in crab ponds, but > 50% in other species ponds. Results indicate that the pollutant loads discharged from aquaculture ponds around Taihu Lake are mild, but precautions are still needed to treat the wastewater. Connecting the ponds in series with crab ponds downstream is a feasible way to decrease pollutant loads. [ABSTRACT FROM AUTHOR]

Abstract: Petrographic features, C, O and Sr isotopes, rare earth and trace elements were determined, and fluid inclusions were analyzed on various stages of interparticle cements and vug-fillings from the Upper Permian and Lower Triassic sour reservoirs in northeastern Sichuan basin. The aim was to assess the origin and evolution of palaeo-waters in the carbonates. The original water was contemporary seawater, from which marine cements precipitated with slightly high Sr contents (mean 1911ppm), 87Sr/86Sr ratios from 0.7067 to 0.7082 and nonluminescent CL. The palaeo-seawater was diluted by meteoric water, as indicated by bright cathodoluminescence (CL) and Sr-depletion (0–516ppm) in low-temperature calcite. When buried to temperatures of about 60–90°C during Middle to Late Triassic, the palaeo-water was enriched in Sr released from the transformation of precursor aragonite and calcite to dolomite, resulting in precipitation of substantial pre-bitumen Sr-rich minerals (SrSO4 and SrCO3). For un-dolomitized limestone sections, aragonite neomorphism may have contributed Sr to the precipitation of small amounts of Sr-bearing minerals and calcite crystals with elevated homogenization temperatures (HTs, mainly from 90 to 130°C) and wide Sr contents (from 34 to 3825ppm), as recorded in stage III calcite. Since the Middle Jurassic, almost all of the early stage celestite and significant amounts of solid CaSO4 have been consumed by reactions with hydrocarbons (i.e., TSR), resulting in water enriched in isotopically light CO2 and and Eu2+, as recorded in calcite with low δ13C values (down to −18.9‰), 87Sr/86Sr ratios from 0.7072 to 0.7076, high HTs (mainly 110–198°C), positive Eu anomalies and high Sr and Ba contents. Subsequently, the water was uplifted and cooled down to about 115°C, celestite and strontianite were precipitated with the occurrence of natural elemental S immiscible inclusions. TSR may have produced significant amounts of freshwater, which brought down Sr concentrations and salinities of the palaeo-waters to not more than about 6.0wt.% NaCl equivalent. [Copyright &y& Elsevier]

Abstract: To reveal the impact of culture condition on the quality of Chinese mitten crabs (Eriocheir sinensis), a study was conducted comparing pond-produced crabs and lake-produced crabs in terms of non-volatile compounds and sensory characteristics, and potential environmental factors were analyzed concurrently. Both groups of crabs were cultured in a similar way, with submerged macrophytes flourishing during most of the cycle. The results showed that the concentrations of total free amino acids (FAAs), umami 5′-nucleotide compounds and poly-unsaturated fatty acids in the hepatopancreas and muscle of pond-produced crab were significantly lower than those of lake-produced crabs. The carotenoid concentrations in the shell and hepatopancreas of pond-produced crabs were significantly lower than those of lake-produced crabs. Significant differences were also observed in terms of shell color, hepatopancreas color and the taste of and preference for the hepatopancreas through sensory evaluation. However, no difference was detected in the taste of muscle. No unpleasant odors or tastes were detected in the muscle or hepatopancreas in either group of crabs. A significantly lower concentration of chlorophyll-a, higher DO and pH values, and poorer biodiversity of microalgae were observed in the pond water compared with lake water; however, no difference in the concentrations of total nitrogen and total phosphorus were detected. It is speculated that the low biodiversity of microalgae and flourishing macrophytes in the ponds contributed directly or indirectly to the faint color as well as the flavor of Chinese mitten crab. [Copyright &y& Elsevier]

U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C-C fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U mineralization. A certain amount of i15:0, a15:0, a17:0 fatty acids coexist with small amounts of i17:1ω7c and 10me16:0, characteristic biomarkers of Desulfovibrio and Desulfobacter sp., respectively. This indicates the existence of sulfate-reducing bacteria (SRB) in the sandstones. The presence of sulfur-oxidizing bacteria (SOB), such as Beggiatoa and Thioploca, is indicated by significant amounts of 16:1ω7c and 18:1ω7c fatty acids. The existence of the SRB in the deposit, as inferred from the fatty acids, is consistent with results from fossilized microorganisms and isotopic compositions of ore-stage pyrite. This suggests that the environment may have been favorable for the SRB to grow since ore formation (9.8-22 Ma). The bacteria may have degraded hydrocarbons directly, or indirectly utilized hydrocarbons degraded by oxic microbes in the deposits. This process may have produced C-rich calcite and prominent baseline humps of unresolved complex mixtures (UCM), and 25-demethylated hopanes and tricyclic terpanes. The existence of sulfur-oxidizing bacteria and sulfate-reducing bacteria in the deposit may have resulted in bacterial sulfate reduction to sulfide, re-oxidization of the sulfide to sulfate and subsequent reduction of the sulfate to sulfide. This assertion is supported by ore-stage pyrite with δS values as low as −39.2‰, and the lightest sulfate (about 11‰) measured during the Phanerozoic, a difference of more than 46‰. [ABSTRACT FROM AUTHOR]

To understand the factors causing frequent outbreaks of harmful algae blooms in the Taihu Lake, China, we studied water quality and nutrient budget in Chinese mitten crab ( Eriocheir sinensis) farm ponds in the eastern part of the lake from November 2007 to December 2009. We estimated the nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) loads. Materials input and output ponds, water exchange, and applied management practices of 838.5-hm crab ponds were surveyed using questionnaires. Water quality of 12 ponds, which were located no more than 2 km from East Taihu Lake, were monitored. The results show that water quality in the crab ponds was better than reference data. Feeds, including corn seed, commercial feed, trash fish, and gastropod, were the major sources of N and P input in the crab ponds, contributing 88.7% and 94.9%, respectively. In total, 60.5% of N and 37.3% of P were sequestered by macrophytes, and only 15.7% and 8.5% of them were discharged as effluent. The net loads of N and P in effluent were 16.43 kg/hm/cycle and 2.16 kg/hm/cycle, respectively, while the COD load was −17.88 kg/hm/cycle. This indicated that crab farming caused minor negative impact on the trophic status of the lake area, which was attenuated by macrophytes. However, wastewater purification is still necessary in crab faming. [ABSTRACT FROM AUTHOR]

Abstract: Solid bitumen, H2S, pyrite and anhydrite samples from the Lower Triassic Feixianguan Formation and Upper Permian Changxing Formation, and source rock kerogen samples from the Cambrian, Ordovician, Silurian and Permian in the East Sichuan Basin were analyzed for their sulfur content and δ34S values, to determine if the measurements were consistent with a thermochemical sulfate reduction (TSR) origin of the produced H2S and solid bitumen. The results show that the solid bitumen samples have sulfur contents from 2.6 to 12.5wt.% and δ34S values from+13.4‰ to+22.1‰. The δ34S values are significantly heavier than those of potential Upper Permian source rock kerogens that average+1.3‰ (n =3), suggesting that most of the sulfur in the solid bitumen is derived from isotopically heavy H2S of TSR origin (from+12.0‰ to+13.7‰). Interestingly, two gases produced from gas to water transition zones during drill stem testing (DST) show significantly lighter δ34S values (+3.3‰ and+4.1‰) than the H2S from gas-producing intervals. The isotopically light H2S may be genetically linked to fracture-filling isotopically heavy anhydrite with δ34S values from+38.5‰ to+39.6‰, which are significantly heavier than those of coeval seawater sulfate (+11.8‰ to+21.7‰) as measured for bedded anhydrite. The link may have resulted from reduction of part of the dissolved sulfate by hydrocarbons under sulfate-limited conditions. Source rock kerogens show a secular change in δ34S values relative to source rock age. A dramatic decrease and then increase in δ34Skerogen was found toward the Permian/Triassic boundary for the first time in the East Sichuan Basin. [Copyright &y& Elsevier]

Abstract: Crude oil, H2S and pyrite samples from Palaeozoic formations in the Tarim Basin have been analyzed for δ 34S values together with oil samples for biomarkers, and fluid inclusions for chemical composition, to elucidate the origin of sulfur in the oil and to address potential applications in oil–source rock correlation. The results show that crude oil samples have sulfur contents from 0.02 to 2.47% and δ 34S values from +11.9 to +28.2‰. Non-degraded oils without associated H2S gas have δ 34S values from +11.9 to +20.5‰, and are relatively rich in C28 ααα 20R sterane, aryl isoprenoids and/or gammacerane. The features are well-correlated with the Cambrian and Lower Ordovician source rocks with δ 34S values from +10.4 to +19.4‰. Non-degraded oils with associated H2S gas have δ 34S values from +15.1 to +19.1‰, close to the H2S (from +15.0 to +18.5‰), suggesting that the H2S was incorporated into the oils, leading to the generation of 2-thiaadamantanes and likely alkyl-thiolanes in the oil with a δ 34S value of +18.5‰. Heavily biodegraded oils have the highest sulfur contents, and show δ 34S values from +20.0 to +28.2‰, significantly heavier than those of any of the potential source rocks (−15.3 to +19.4‰). Thus, it is likely that isotopically heavy sulfides have been incorporated into the biodegraded oils, resulting in δ 34S values of the oils becoming closer to Cambrian and Ordovician age seawater sulfates. The sulfides may have originated from thermochemical sulfate reduction (TSR), as evidenced by the occurrence of H2S-rich fluid inclusions and late-stage and fracture-filling pyrite with δ 34S values mainly from +25 to +34‰ in the Palaeozoic reservoirs. [Copyright &y& Elsevier]

Abstract: The reported source rocks for the abundant petroleum in the Tarim Basin, China range from Cambrian to Lower Ordovician and/or Upper Ordovician in age. However, the difference between the two groups of source rocks is not well characterized. In this study, pyrite was removed from eleven mature to over mature kerogen samples from source rocks using the method of CrCl2 reduction and grinding. The kerogen and coexisting pyrite samples were then analyzed for δ 34S values. Results show that the kerogen samples from the Cambrian have δ 34S values between +10.4‰ and +19.4‰. The values are significantly higher than those from the Lower Ordovician kerogen (δ 34S of between +6.7‰ and +8.7‰), which in turn are generally higher than from the Upper Ordovician kerogen samples (δ 34S of between −15.3 and +6.8‰). The associated pyrite shows a similar trend but with much lower δ 34S values. This stratigraphically controlled sulfur isotope variation parallels the evolving contemporary marine sulfate and dated oil δ 34S values from other basins, suggesting that seawater sulfate and source rock age have an important influence on kerogen and pyrite δ 34S values. The relatively high δ 34S values in the Cambrian to Lower Ordovician source rocks are associated with abundant aryl isoprenoids, gammacerane and C35 homohopanes in the extractable organic matter, indicating that these source rocks were deposited in a bottom water euxinic environment with water stratification. Compared with the Upper Ordovician, the Cambrian to Lower Ordovician source rocks show abundance in C28 20R sterane, C23 tricyclic terpanes, 4,23,24-trimethyl triaromatic dinosteroids and depletion in C24 tetracyclic terpane, C29 hopane. Thus, δ 34S values and biomarkers of source rock organic matter can be used for distinguishing the Cambrian and Upper Ordovician source rocks in the Tarim Basin. [Copyright &y& Elsevier]

Abstract: Rare earth elements, δ 34S, 87Sr/86Sr and δ 18O were determined, and fluid inclusions were analyzed of fracture filling barite, anhydrite, fluorite, calcite and quartz from Upper Ordovician carbonates in Central Tarim, China. The aim was to assess the origin, evolution and flow of fluid in the fractures. There was mixing of relatively hot Ba-rich and 87Sr-rich fluid with in situ basinal water and fresh water which was relatively cool and more radiogenic. The hotter fluid is hydrothermal as indicated by homogenization temperatures (HTs) about 20°C higher than the formation, and was most likely derived from Precambrian to Lower Cambrian clastic rocks or/and from the basement through faults. This is because almost all of 87Sr/86Sr ratios of late stage fracture-fillings (mainly 0.70889–0.71036) and present brines are higher than that of Upper Ordovician limestones. The hydrothermal fluid was enriched in F−, Eu2+, Ba2+, Sr2+ and Zn2+ during migration as indicated by the positive relationships of Eu to Sr, Ba and Zn. When the hydrothermal fluid mixed with local basinal water, it precipitated isotopically-normal S anhydrite, fluorite and calcite with positive Eu anomalies. The precipitation of these Ca-minerals was followed by thermochemical SO4 reduction (TSR) of dissolved sulphates by hydrocarbons. It was likely that only part of the was reduced and the generated H2S leaked out, thus barite deposited from residual has abnormally high δ 34S values from 42‰ to 47‰ and the generated H2S is isotopically light from 15‰ to 18‰. Subsequently, hydrothermal fluid was likely to have mixed with relatively cool and more 87Sr-rich freshwater, resulting in precipitation of quartz and fluorite with salinities as low as 0.5wt% NaCl equiv. and 87Sr/86Sr ratios up to 0.71036. [Copyright &y& Elsevier]

Abstract: Sandstone-hosted roll-type U deposits has recently been found in the Middle Jurassic Zhiluo Formation in the Dongsheng area, north of the Ordos Basin. In order to assess the origin of the uranium mineralization, the host sandstone has been investigated, with emphasis on δ 34 S values of ore-stage pyrite, δ 13 C of calcite, fluid inclusion oil biomarkers, X-ray diffraction, ICP-MS, as well as studies by electron microprobe and scanning electron microscope. The mineralization consists mainly of coffinite. Some of the coffinite is intimately intergrown with ore-stage pyrite, indicating co-precipitation. Ore-stage pyrite has δ 34 S values from −34 to +17‰, suggesting the pyrite sulfur originated from bacterial sulfate reduction. In the host sandstone, calcite cement exhibits δ 13 C values from −27.6 to −2.1‰ and fluid inclusion oils show evidence of biodegradation. These lines of evidence indicate petroleum was likely oxidized by sulfate-reducing bacteria (SRB) and thus supplied a source of some of the carbon in the calcite. Microbial degradation of petroleum is partially supported by the low-temperature diagenetic environment (<70 °C). Thus, SRB were likely to reduce sulfates to sulfides simultaneously with petroleum oxidization, and caused direct or indirect reduction of hexavalent uranium [U(VI)] to tetravalent uranium [U(IV)]. U(VI) pre-concentration by adsorption and subsequent inorganic reduction is likely to be less significant than direct reduction of U(VI) by SRB in the Dongsheng deposit. This is because ore-stage solution is non-acidic (pH=8 to 10), as indicated by abundance of ore-stage pyrite and calcite cement and lack of marcasite in the host sandstone. [Copyright &y& Elsevier]

Abstract: Unusual mineral structures have recently been found in a sandstone-hosted roll-type uranium deposit in the Middle Jurassic Zhiluo Formation in the Shashagetai deposit, the northern Ordos basin, NW China. The structures possess a chemical composition and crystal structure characteristic of mineral coffinite [(USiO4)1−x (OH)4x ], which occurs as nanoparticles with size ranging from 5 to 25 nm. These structures are interpreted to be fossilized microorganisms, based on mineralogical biosignatures including morphology, size, occurrence of biogenic coffinite as nano-crystals, and biological elements such as P. The intimate intergrowth of coffinite with secondary pyrite of bacterial origin, as defined by low δ 34S values, and calcite cements with petroleum-derived carbon supports its biogenic origin. Oil inclusions in the host sandstone are characterized by abundant n-alkanes, slightly increased Pr/nC17 and Ph/nC18 ratios, significant amounts of demethylated hopanes and tricyclic terpanes, and the existence of unresolved complex mixtures. These characteristics are interpreted to be a result of mixing of an earlier, heavily degraded oil with a later charged fresh oil; subsequently the oils were slightly degraded. These lines of evidence lead to the proposal that the reduction of sulfate and oxidization of petroleum are likely synchronous with reduction of hexavalent [U(VI)] to tetravalent [U(IV)] uranium by sulfate-reducing bacteria (SRB). The discovery of a natural association of microorganism-like structures, a uranium mineral, and biodegraded petroleum has implications for uranium biomineralization and fossil fuel exploration. [Copyright &y& Elsevier]