Variation of wind speed and the physico-chemical parameters,such as dissolved phosphate,ferrous and manganese in lake water were observed on site.Together with the chemistry analysis and simulated experiment in lab,th...Variation of wind speed and the physico-chemical parameters,such as dissolved phosphate,ferrous and manganese in lake water were observed on site.Together with the chemistry analysis and simulated experiment in lab,the change of phosphate concentration in lake water was analyzed.The variation of ferrous/phosphate ratio explained that along with the enhancement of wind-wave effect and the oxidation ability of lake water,the effects of co-precipitation and removal of dissolved phosphate and iron in the lake water were reinforced.The ferrous/phosphate ratio in pore water was less than 2.0,demonstrating that the dissolved phosphate can be released into the overlying water.But,in the lake water,the stability of phosphate was controlled by the water dynamics.The phosphate release experiment showed that molecular release was only part of the whole and the direct discharge of phosphate in the pore water was also a part.The mineralization and biological process of suspended particulates in the water may be another important reason for the whole phosphate loadings.展开更多
Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permia...Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary （PTB） in the shallow platform interior at Great Bank of Guizhou （GBG） has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur （total sulfur （TS） and pyrite sulfur （Spy）） concentrations, low Spy/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high Spy/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin： the intense volcanic eruptions, which release huge COz and SO2 before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon iso- topic negative excursion and the expansion of the ocean oxygen minimum zone （OMZ）. When the OMZ expanded into the photic zone, the episodic H2S release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic- anoxic shallow water.展开更多
A suite of oils and bitumens from the Eocene Shahejie Formation(Es) in Dongying Depression was geochemically characterized to illustrate impact of source input and redox conditions on distributions of pentacyclic terp...A suite of oils and bitumens from the Eocene Shahejie Formation(Es) in Dongying Depression was geochemically characterized to illustrate impact of source input and redox conditions on distributions of pentacyclic terpanes. The Es_(4) developed under highly reducing, sulfidic hypersaline conditions, while Es_(3) formed under dysoxic, brackish to freshwater conditions. Oils derived from Es_(4) are enriched in C_(32) homohopanes(C_(32) H), while those from Es_(3) are prominently enriched in C_(31) homohopanes(C_(31) H). The C_(32) H/C_(31) H ratio shows positive correlation with homohopane index(HHI), gammacerane index, and negative correlation with pristane/phytane ratio, and can be used to evaluate oxic/anoxic conditions during deposition. High C32 H/C_(31) H ratio(> 0.8) is an important characteristic of oils derived from anoxic environments, while low values(< 0.8) indicate dysoxic conditions and extremely low values(< 0.4)indicate strong oxic conditions. The C_(32) H/C_(31) H ratio can be applied for deposition condition diagnosis because carboxyl group of C_(32) hopanoic acids might be reduced to C_(32) homohopanes under anoxic conditions, and oxidized to C_(31) homohopane under oxic conditions. Advantages to use C_(32) H/C_(31) H ratio as redox condition proxy compared to the HHI and gammacerane indexes are wider valid maturity range,less sensitive to biodegradation influence and better differentiating reducing from oxic environments.展开更多
Underground brine samples were collected along the southern coast of the Laizhou Bay, Shangdong, China in two field investigations in 2003. The brines are confined in the Quaternary sediment and underwent a series of ...Underground brine samples were collected along the southern coast of the Laizhou Bay, Shangdong, China in two field investigations in 2003. The brines are confined in the Quaternary sediment and underwent a series of geochemical changes. The redox states of these brines were assessed qualitatively based on the measurements of Eh and redox-sensitive species such as DO, NO NO~, Mn2＋, Fe2＋, SO4^2- in the brines. The redox condition of the underground brine is anoxic, and the redox reactions that controlled the redox potential of brines should be Fe（Ⅲ） reduction and sulfate reduction.展开更多
Arsenic(As)contamination is one of the major factors that contribute to environmental pollution,and it plays havoc with sustainability of crop production.Nano-hydroxyapatite(nHAP)can be an effective phosphorus(P)sourc...Arsenic(As)contamination is one of the major factors that contribute to environmental pollution,and it plays havoc with sustainability of crop production.Nano-hydroxyapatite(nHAP)can be an effective phosphorus(P)source to cope with As toxicity.The mitigating effects of variable P sources on As toxicity in rice,sunflower,and maize grown in an alkaline soil were evaluated.Arsenic was applied at 0 and 20 mg kg^(-1),and P was applied at 0,50,and 500 mg kg^(-1)in the forms of triple superphosphate(TSP)and nHAP.In addition,the same amount of phosphoric acid was also used in the sunflower and maize experiments with the other P sources.The structural and functional properties of nHAP were determined by Fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.Stunted growth was observed in rice,and less in sunflower;maize remained unaffected by As toxicity.In the presence of As,TSP and nHAP at their high doses(500 mg kg^(-1))significantly increased the rice dry weight compared with the control(0 mg kg^(-1)).The As concentration in rice was decreased by approximately 25%in the presence of 50 mg kg^(-1)TSP and 500 mg kg^(-1)nHAP.The P treatments had no significant effect on the As concentration in sunflower,whereas the As concentration in maize was increased by 500 mg kg^(-1)TSP.In the absence and presence of As,nHAP at 50 mg kg^(-1)significantly increased rice P concentration,whereas in the presence of As,500 mg kg^(-1)TSP significantly increased P concentration in rice compared with the control.Arsenic had no significant effect on sunflower P concentration,while the maize P concentration was decreased in the 0 mg kg^(-1)P treatment.It can be concluded that TSP and nHAP were effective in alleviating As toxicity in rice and sunflower.Comparative studies are further needed to determine the long-term effects of TSP and nHAP on prevention of As toxicity in field conditions.展开更多
Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of th...Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of these targets and associated risks.Assessing shale depositional environments is also challenging due to the fine-grained nature of the sediments and subtle compositional variations.Herein,marine black shales of the Lower Cambrian Shiyantou(SYT)Formation(Fm)and Yu'anshan(YAS)Fm are investigated through a series of experiment,including thin sections,scanning electron microscopy,and major and trace elements analysis.Results show that five lithofacies can be identified in the SYT and YAS shales:(1)calcareous mudstone;(2)wavy-laminated sand,silt,and clay bearing mudstone;(3)laminated and massive mudstone;(4)planar-laminated pyritic mudstone,and(5)thin bedded sand and siltstone.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of SYT Fm are 57.03%,12.74%,4.20%,3.97%,3.93%,3.35%,1.09%,0.68%,0.28%,and 0.05%,respectively.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of Yu'anshan Fm are 54.93%,14.52%,5.26%,6.00%,3.77%,3.88%,0.15%,0.63%,0.19%,and 0.10%,respectively.Samples from SYT Fm are enriched in Li,V,Cr,Co,Zr,Cs,and U relative to Upper Continental Crust(UCC)and most of shale samples from YAS Fm are enriched in Li,V,Co,and U relative to UCC.The marine black shales are deposited in dynamic anoxic to oxic environment in upper Yangtze Plate,which indicated the seabed had already oxidized in the Cambrian Stages 2 and 3.The Chemical Index of Alteration(CIA)values ranged 51.84–79.46 indicate a warm and humid climate in the 2 stages.These findings are consistent with the region's paleogeography and previous studies.They hold significance for sedimentologists,paleontologists,and other researchers involved in petroleum geology.展开更多
Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but ...Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but with strong heterogeneity. Through the analysis of trace elements, organic macerals and biomarkers, it is indicated that plankton has made little contribution to Oligocene source rocks compared with the terrestrial higher plants. The organic matter preservation depends on hydrodynamics and the redox environment, and the former is the major factor in the study area. During the sedimentary period of the Yacheng Formation, tidal flats were developed in the central uplift zone, where the hydrodynamic conditions were weak and the input of terrestrial organic matter was abundant. So the Yacheng Salient of the central uplift zone is the most favorable area for the development of source rocks, followed by the central depression zone. During the sedimentary period of the Lingshui Formation, the organic matter input was sufficient in the central depression zone due to multiple sources of sediments. The semi-enclosed environment was favorable for organic matter accumulation, so high quality source rocks could be easily formed in this area, followed by the Yacheng salient of central uplift zone. Source rocks were less developed in the northern depression zone owing to poor preservation conditions,展开更多
The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic m...The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.展开更多
The Middle Permian Lucaogou Formation is the source rock and the main oil shale producing formation in the southeastern Junggar Basin.This study focused on the Lucaogou Formation exposed in two outcrop sections on the...The Middle Permian Lucaogou Formation is the source rock and the main oil shale producing formation in the southeastern Junggar Basin.This study focused on the Lucaogou Formation exposed in two outcrop sections on the northern flank of the Bogda Mountain,namely the Jingjingzigou and Dalongkou sections.Here,we present integrated analysis of the sedimentology,major and trace elements,mineral components and total organic carbon contents.The paleo-environment was reconstructed including provenance,redox conditions,paleo-salinity,chemical weathering intensity and primary organic matter productivity.The results showed that the upper and lower units were deposited in distinct depositional environments with different organic matter accumulation mechanisms.The lower unit was characterized by low lake level,dry climate,fresh-brackish and well-oxygenated water.While during the deposition of the upper unit the lake level rose,climate turned wetter and the bottom water became less oxidized and much saltier.The mechanism of the organic matter accumulation is different for these two units.The preserved organic matters were mainly controlled by the primary productivity in the lower unit and by the redox conditions in the upper unit.展开更多
The beginning of the Phanerozoic was marked by abundant phytoplankton,the occurrence of animals and a newly established ecosystem structure,which in turn,resulted in different modes of organic matter(OM)cycling and pr...The beginning of the Phanerozoic was marked by abundant phytoplankton,the occurrence of animals and a newly established ecosystem structure,which in turn,resulted in different modes of organic matter(OM)cycling and preservation.In this study,we present an integrated paleontological and geochemical study of the Lower Cambrian Yanjiahe and Shuijingtuo formations in the Three Gorges area,South China.Rock samples were analyzed for major and trace elements,in order to evaluate the marine productivity.Fossil samples were recovered using palynological methods,destructive analytical techniques,SEM analysis and thin section microscopy.The organic-walled microfossils in the investigated sections include marine microphytoplankton,linings of sponge spicules,small shelly fossils and some unnamed sheet-like and net-like microfossils(animal parts).Additionally,fecal structures and coprolites fossils were found.Three intervals in the Luojiacun Section were proposed to discuss the links among microfossil assemblages and their influence on OM cycling and preservation.We found that the marine microphytoplankton was the main source of OM in the investigated sections.The appearance of fecal structures groups and massive appearance of animals in the pelagic zone indicate a higher transfer efficiency of OM aggregates through the water column.Oxygenated conditions in the water-column would have led to a moderate to low preservation of OM,an effect which would have been further enhanced by the potential presence of bioturbators.Overall,our study reveals the contribution of various organisms to the sedimentary OM and highlights the links and feedbacks among microfossil assemblages,OM recycling efficiency and OM preservation in the tipping point of the Phanerozoic“new world”.展开更多
Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reduc...Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.展开更多
Nitrogen isotope compositions(δ15N)of sedimentary rocks are usually used to reconstruct the paleoenvironment and nitrogen(N)biogeochemical cycle.Theδ15N values of crude oils inherit the characteristics of relevant s...Nitrogen isotope compositions(δ15N)of sedimentary rocks are usually used to reconstruct the paleoenvironment and nitrogen(N)biogeochemical cycle.Theδ15N values of crude oils inherit the characteristics of relevant source rocks and can well reflect the information of hydrocarbon-forming organisms and environment in ancient water column.However,studies on theδ15N of crude oils are limited due to the low N content.In this study,a new efficient method is applied to the marine oils from the Bashituo(BST)and Halahatang(HLHT)areas of the Tarim Basin to obtain the nitrogenous components(i.e.,nonhydrocarbons and asphaltenes)for the achievement of N concentration.The carbon and nitrogen isotopes of these components and the biomarkers of oils were measured.Theδ15N values in asphaltenes(δ15NAsp)are significantly heavier than those in nonhydrocarbons(δ15NNSOs)in these oils,which are attributed to the potential directional N transfer and kinetic isotope fractionation during the thermal evolution of organic matters(OM).Theδ15NAspvalues have significant correlations with OM origin associated parameters and weak correlations with environmental parameters,suggesting that the difference inδ15NAspvalues is mainly resulted from biological source rather than redox conditions.Theδ15NNSOsvalues have a closer relationship with the redox condition than biological characteristics,indicating that they have a good response to paleoenvironmental variation in the water column,which is not completely overprinted by the difference of OM origin.Different redox conditions give rise to distinct nitrogen cycles,resulting in variousδ15N values.Anammox occurs in the water column of the Early Cambrian dominated by physically stratified conditions with significant isotope fractionation,resulting in relatively heavierδ15N of OM in the BST area.In the Middle-Late Ordovician period,the limited suboxic zone leads to an insignificant positive bias ofδ15N caused by partial denitrification in the HLHT oils.The evaluation ofδ15N in nitrogenous fractions enables a more comprehensive reconstruction of N cycle for ancient oceans.展开更多
With the global vigorous development of high-tech industries,the market demand for rare earth elements and Yttrium(REY)have experienced explosive growth.In recent years,phosphate associated REY resources(up to 18,000 ...With the global vigorous development of high-tech industries,the market demand for rare earth elements and Yttrium(REY)have experienced explosive growth.In recent years,phosphate associated REY resources(up to 18,000 ppm)found in modern deep-sea muds have attracted significant attentions.It is believed that their REY originated directly from porewater in deep-sea sediments,with a process of detrital dissolution releasing REY into the porewater.However,it remains unclear whether this model could be applied to REY-rich phosphorites from geological history,which contrasts sharply with the widely accepted Fe-oxide redox pump model at the seawater-sediment interface.Here,we present the mineralogy and REY geochemistry of clay minerals,and whole-rock Si-Fe isotopic compositions(δ^(30)Si and δ^(56)Fe)from early Cambrian REY-rich Zhijin phosphorite(∑REY,~2000 ppm)and REY-poor Meishucun phosphorite(∑REY,<400 ppm)in South China.In the Zhijin samples,illite formed around the edges of muscovite,exhibiting seawater-like REY patterns.In contrast,muscovite and orthoclase in the Meishucun samples show no contact relationship and display REY patterns typical of granite-forming minerals.The REY contents(reach 310 ppm)of muscovites from Zhijin samples are much higher than that of detrital muscovite(REY,0.09-5.86 ppm)and orthoclase(REY,2.69-6.45 ppm)from Meishucun samples.Furthermore,the data can be classified into two categories based on the correlation between δ^(30)Si values and phosphate-hosted REY enrichment in Zhijin and Meishucun samples.One is characterized by higher δ^(30)Si values(average 0.6‰)and Y/Ho ratios(average 56),and lower SiO_(2)and REY contents(average 8.10% and 1076 ppm,respectively).The other group exhibits lower δ^(30)Si values(average 0.2‰)and Y/Ho ratios(average 52),and higher SiO_(2)and REY contents(average 17.45% and 2085 ppm,respectively).In addition,compared to the Meishucun phosphorites formed in well oxidized marine environment(δ^(56)Fe,~0‰),the Zhijin phosphorites developed under fluctuating oxic-suboxic marine condition exhibit a significant negative correlation between Fe and Si isotopic compositions.These findings indicate Zhijin muscovite underwent REY exchange with seawater under fluctuating redox marine conditions,leading to REY release into the porewater and the formation of authigenic illite.This process did not occur in the Meishucun samples.It's well known that continental weathering transformed feldspar into REY-rich muscovite or illite.These REY-rich clays,transported to the seawater-sediment interface,were dissolved and released REY into the porewater within a fluctuating oxic-suboxic marine environment.We proposed for the first time that fluctuating marine redox conditions acted as a trigger for REY enrichment in ancient phosphorites,with the primary REY source being terrigenous REY-rich clay.This perspective not only provides an insight into the mechanism of REY enrichment in phosphorites,but could also account for the lack of anomalous REYenrichment in phosphorites exhibiting the precipitation of extensive pyrites if only Fe-oxide redox processes are considered.展开更多
The change of the primary productivity across the Permian-Triassic boundary （PTB） remains controversial. In this study, records from two deep-water sections in South China （Xiakou and Xinmin sections） show the pri...The change of the primary productivity across the Permian-Triassic boundary （PTB） remains controversial. In this study, records from two deep-water sections in South China （Xiakou and Xinmin sections） show the primary productivity decreased gradually from the latest Permian to the earliest Triassic, and five evolutionary stages Increase-Decrease-Recovery-Recession- Stagnation） can be observed from Clarkina changxingensis-C, deflecta to Hindeodus parvus-lsarcicella isarcica zones. Pri- mary productivity decreased abruptly from the base of C. meishanensis zone. Besides, for adjusting to the deterioration of the oceanic environment, the primary producers in the oceanic surface had changed to acritarch and cyanobacteria, which were more tolerant of stressful environment. Then the producers were under huge stagnation in the H. parvus-L isarcica zone. The values of quantitative calculation of the primary productivity from the black rock series in the Dalong Formation were very high, corresponding to that of an upwelling area in modern ocean, which shows that the strata of the Dalong Formation in the study region are potential hydrocarbon source-rocks. This result may come from the fact that South China craton was located at the equatorial upwelling area during the Permian-Triassic transitions. But organic matter contents were different in various sections because they could be affected by redox conditions and diagenesis process after burial.展开更多
This study presents geochemical characteristics of glauconites in estuarine deposits within the Maastrichtian Lameta Formation in central India. Resting conformably over the Bagh Group, the Lameta Formation consists o...This study presents geochemical characteristics of glauconites in estuarine deposits within the Maastrichtian Lameta Formation in central India. Resting conformably over the Bagh Group, the Lameta Formation consists of ~4-5 m thick arenaceous, argillaceous and calcareous green sandstones underlying the Deccan Traps. The sandstone is friable, medium-to coarse-grained, well-sorted and thoroughly crossstratified, and contains marine fossils. Detailed petrography, spectroscopy and mineral chemistry indicates unique chemical composition of glauconite with high KO, MgO, AlOand moderate TFeO. Glauconite is formed by the replacement of K-feldspars, initially as stringers in the cleavages and fractures of feldspars. Incipient glauconite subsequently evolves fully, appearing as pellets. Fully-evolved glauconite pellets often leave tiny relics of K-feldspar. XRD exhibits characteristic peak of 10A from basal(001)reflection of glauconite, indicating the "evolved" character. The KO content of glauconites in the Lameta Formation varies from 5.51% to 8.29%, corroborating the "evolved" to "highly-evolved" maturation stage.The TFeOcontent of glauconite varies from 12.56% to 18.90%. The PASS-normalized-REE patterns of glauconite exhibit a "hat-shape" confirming the authigenic origin of glauconites. The slightly-negative to slightly-positive Ce anomaly value and the moderate TFeOcontent of glauconite agree well with a suboxic,estuarine condition. The replacement of K-feldspar by the glauconite contributes towards the high KO content. Compositional evolution of glauconites in the Lameta Formation is similar to those observed in many Precambrian sedimentary sequences.展开更多
Results of Mossbauer spectroscopy and ICP-AES measurement revealed a special distribution pattern of iron species in four crossing profiles of the Tertiary Formation Type of Landslides in Japan. In comparison with hos...Results of Mossbauer spectroscopy and ICP-AES measurement revealed a special distribution pattern of iron species in four crossing profiles of the Tertiary Formation Type of Landslides in Japan. In comparison with host rocks, the sliding mud in the landslide slip zone contains the higher ferrous iron content and/or trace pyrite, which indicates that the forming environment was relatively reducing. The total iron content also increased with an increase in ferric iron and pyrite, in contrast, decreased with an increase in ferrous iron content. The deep-gray and black mud layers formed and accumulated in various volumes within landslide slip zones are treated as the basic criteria for the slipping activity, because the soft mud saturated with groundwater is easy to create a plastic deformation.展开更多
Formation of organic-rich shale was controlled by depositional processes and environment condition.According to petrology,mineralogy,fossil composition and sedimentary structure,seven lithofacies of shale were identif...Formation of organic-rich shale was controlled by depositional processes and environment condition.According to petrology,mineralogy,fossil composition and sedimentary structure,seven lithofacies of shale were identified in the Wufeng Formation to Longmaxi Formation,e.g.,siliceous shale,silty shale,argillaceous shale,calcareous shale,shell-bearing argillaceous limestone/calcareous mudstone,siltstonefine sandstone and bentonite.For shale in the Wufeng and Longmaxi Formations,the depositional mode was not only the suspension deposition under the low-energy hydrodynamic condition,but also the biogenic deposition,the storm deposition and the bottom current deposition indicated by large amount of siliceous biological fossils,biological detritus with size graded structure,silt laminations,lenticular bedding,ripple cross-bedding and other sedimentary structures.Trace element analysis suggested that the siliceous shale in theWufeng Formation and the lower part of Longmaxi Formation was developed in the oxygen-dysoxic/anoxic depositional environment,which was rich in organic matters;then due to influence of the sea level gradually decline and bottom current,the silty and argillaceous shales were formed,and the oxygen-dysoxic/anoxic depositional environment was destroyed,gradually leading to the worse preservation condition of organic matter.展开更多
Isoprenoid and branched glycerol dialkyl glycerol tetraethers （GDGTs） lipids were studied in flooded and non-flooded paddy soil in Wuhan, central China, to examine the response of the GDGTs distribution to the soil ...Isoprenoid and branched glycerol dialkyl glycerol tetraethers （GDGTs） lipids were studied in flooded and non-flooded paddy soil in Wuhan, central China, to examine the response of the GDGTs distribution to the soil flooding. Samples were collected before and after the soil flooding in four specific months. Both core （CL） and intact polar （IPL） GDGTs were quantified. Increase in the abundance of archaeol and caldarchaeol may be indicative of the occurrence of methanogens in the flooded soil. A negative correlation was observed between the ratio of IPL branched GDGT-IIa to GDGT-Ia and the soil pH. The rise of the soil pH in the acid soil is known to be controlled by the redox conditions resulting from flooding. Thus, the branched GDGTs distribution may be controlled by the water content in the paddy soil. In addition, we suggest that the anoxic conditions resulting from flooding may also control the abundance of branched GDGTs relative to crenarchaeol, which in turn results in the increase of branched and isoprenoidal tetraethers （BIT） values, the index for the terrestrial input to the marine sediments.展开更多
It is essential to investigate shale lithofacies distribution and controlling factor of the shale for geological evaluation of shale gas exploration and development.Through comprehensive analysis of cores,thin section...It is essential to investigate shale lithofacies distribution and controlling factor of the shale for geological evaluation of shale gas exploration and development.Through comprehensive analysis of cores,thin sections,cathode luminescence,whole-rock X-ray diffraction,element capture spectroscopy,major/trace element and other data,three major types and eight sub-type shale lithofacies in the shale of Wufeng Formation-Member 1 of Longmaxi Formation in Jiaoshiba area are identified by the three-end-member method and shale lithological classification nomenclature,and the spatiotemporal distribution law and main development controlling factors of shale lithofacies are well studied.In the Jiaoshiba area,vertically,the marine shale develops siliceous shale,mixed shale and argillaceous shale from bottom to top.Besides,lateral distribution of the shale is different from north to south;the shale lithofacies in the north area changes rapidly,the mixed shale in the north area is much thicker than that in the south area,while the siliceous shale in the south area is relatively thicker.Difference in the shale lithofacies is controlled by special sedimentary geologic events;development of the siliceous shale is controlled by the Ordovician-Silurian global volcanic event to some extent,while the mixed shale is significantly influenced by effect of bottom current,and the argillaceous shale is mainly affected by supply of terrestrial clastic material.展开更多
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX1-SW-12)the National Natural Science Foundation of China(Grant No.40501064)the State Key Project of Science and Technology in"Tenth Five-Year Plan"of China,"863"(Grant No.2002AA601013).
文摘Variation of wind speed and the physico-chemical parameters,such as dissolved phosphate,ferrous and manganese in lake water were observed on site.Together with the chemistry analysis and simulated experiment in lab,the change of phosphate concentration in lake water was analyzed.The variation of ferrous/phosphate ratio explained that along with the enhancement of wind-wave effect and the oxidation ability of lake water,the effects of co-precipitation and removal of dissolved phosphate and iron in the lake water were reinforced.The ferrous/phosphate ratio in pore water was less than 2.0,demonstrating that the dissolved phosphate can be released into the overlying water.But,in the lake water,the stability of phosphate was controlled by the water dynamics.The phosphate release experiment showed that molecular release was only part of the whole and the direct discharge of phosphate in the pore water was also a part.The mineralization and biological process of suspended particulates in the water may be another important reason for the whole phosphate loadings.
基金supported by National Basic Research Program of China (Grant No. 2011CB808800)National Natural Science Foundation of China (Grant Nos. 41172312, 41272372, 41172036, 41240016, 41302271)+1 种基金Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan)Fund of State Key Laboratory of Biogeology and Environmental Geology (Grant No. BGEG1016)
文摘Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary （PTB） in the shallow platform interior at Great Bank of Guizhou （GBG） has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur （total sulfur （TS） and pyrite sulfur （Spy）） concentrations, low Spy/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high Spy/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin： the intense volcanic eruptions, which release huge COz and SO2 before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon iso- topic negative excursion and the expansion of the ocean oxygen minimum zone （OMZ）. When the OMZ expanded into the photic zone, the episodic H2S release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic- anoxic shallow water.
基金supported by National Natural Science Foundation of China (Grant number 41873049)China Postdoctoral Science Foundation (2021M700538)。
文摘A suite of oils and bitumens from the Eocene Shahejie Formation(Es) in Dongying Depression was geochemically characterized to illustrate impact of source input and redox conditions on distributions of pentacyclic terpanes. The Es_(4) developed under highly reducing, sulfidic hypersaline conditions, while Es_(3) formed under dysoxic, brackish to freshwater conditions. Oils derived from Es_(4) are enriched in C_(32) homohopanes(C_(32) H), while those from Es_(3) are prominently enriched in C_(31) homohopanes(C_(31) H). The C_(32) H/C_(31) H ratio shows positive correlation with homohopane index(HHI), gammacerane index, and negative correlation with pristane/phytane ratio, and can be used to evaluate oxic/anoxic conditions during deposition. High C32 H/C_(31) H ratio(> 0.8) is an important characteristic of oils derived from anoxic environments, while low values(< 0.8) indicate dysoxic conditions and extremely low values(< 0.4)indicate strong oxic conditions. The C_(32) H/C_(31) H ratio can be applied for deposition condition diagnosis because carboxyl group of C_(32) hopanoic acids might be reduced to C_(32) homohopanes under anoxic conditions, and oxidized to C_(31) homohopane under oxic conditions. Advantages to use C_(32) H/C_(31) H ratio as redox condition proxy compared to the HHI and gammacerane indexes are wider valid maturity range,less sensitive to biodegradation influence and better differentiating reducing from oxic environments.
文摘Underground brine samples were collected along the southern coast of the Laizhou Bay, Shangdong, China in two field investigations in 2003. The brines are confined in the Quaternary sediment and underwent a series of geochemical changes. The redox states of these brines were assessed qualitatively based on the measurements of Eh and redox-sensitive species such as DO, NO NO~, Mn2＋, Fe2＋, SO4^2- in the brines. The redox condition of the underground brine is anoxic, and the redox reactions that controlled the redox potential of brines should be Fe（Ⅲ） reduction and sulfate reduction.
文摘Arsenic(As)contamination is one of the major factors that contribute to environmental pollution,and it plays havoc with sustainability of crop production.Nano-hydroxyapatite(nHAP)can be an effective phosphorus(P)source to cope with As toxicity.The mitigating effects of variable P sources on As toxicity in rice,sunflower,and maize grown in an alkaline soil were evaluated.Arsenic was applied at 0 and 20 mg kg^(-1),and P was applied at 0,50,and 500 mg kg^(-1)in the forms of triple superphosphate(TSP)and nHAP.In addition,the same amount of phosphoric acid was also used in the sunflower and maize experiments with the other P sources.The structural and functional properties of nHAP were determined by Fourier transform infrared spectroscopy,X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.Stunted growth was observed in rice,and less in sunflower;maize remained unaffected by As toxicity.In the presence of As,TSP and nHAP at their high doses(500 mg kg^(-1))significantly increased the rice dry weight compared with the control(0 mg kg^(-1)).The As concentration in rice was decreased by approximately 25%in the presence of 50 mg kg^(-1)TSP and 500 mg kg^(-1)nHAP.The P treatments had no significant effect on the As concentration in sunflower,whereas the As concentration in maize was increased by 500 mg kg^(-1)TSP.In the absence and presence of As,nHAP at 50 mg kg^(-1)significantly increased rice P concentration,whereas in the presence of As,500 mg kg^(-1)TSP significantly increased P concentration in rice compared with the control.Arsenic had no significant effect on sunflower P concentration,while the maize P concentration was decreased in the 0 mg kg^(-1)P treatment.It can be concluded that TSP and nHAP were effective in alleviating As toxicity in rice and sunflower.Comparative studies are further needed to determine the long-term effects of TSP and nHAP on prevention of As toxicity in field conditions.
基金Supported by the National Natural Science Foundation of China(Nos.42130206,41302076)the Ministry of Science and Technology of the People’s Republic of China(MOST)Special Fund+1 种基金the State Key Laboratory of Continental Dynamics,Northwest University(No.201210128)the Major Scientific and Technological Projects of Changqing Oilfield(No.ZDZX-2021-03)。
文摘Early Cambrian organic-rich shales in the Yangtze Plate are key shale gas exploration targets in China,but their sedimentary environments are not well understood.This lack of knowledge complicates the evaluation of these targets and associated risks.Assessing shale depositional environments is also challenging due to the fine-grained nature of the sediments and subtle compositional variations.Herein,marine black shales of the Lower Cambrian Shiyantou(SYT)Formation(Fm)and Yu'anshan(YAS)Fm are investigated through a series of experiment,including thin sections,scanning electron microscopy,and major and trace elements analysis.Results show that five lithofacies can be identified in the SYT and YAS shales:(1)calcareous mudstone;(2)wavy-laminated sand,silt,and clay bearing mudstone;(3)laminated and massive mudstone;(4)planar-laminated pyritic mudstone,and(5)thin bedded sand and siltstone.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of SYT Fm are 57.03%,12.74%,4.20%,3.97%,3.93%,3.35%,1.09%,0.68%,0.28%,and 0.05%,respectively.Average content of major elements SiO_(2),Al_(2)O_(3),MgO,Fe_(2)O_(3),K_(2)O,CaO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO of Yu'anshan Fm are 54.93%,14.52%,5.26%,6.00%,3.77%,3.88%,0.15%,0.63%,0.19%,and 0.10%,respectively.Samples from SYT Fm are enriched in Li,V,Cr,Co,Zr,Cs,and U relative to Upper Continental Crust(UCC)and most of shale samples from YAS Fm are enriched in Li,V,Co,and U relative to UCC.The marine black shales are deposited in dynamic anoxic to oxic environment in upper Yangtze Plate,which indicated the seabed had already oxidized in the Cambrian Stages 2 and 3.The Chemical Index of Alteration(CIA)values ranged 51.84–79.46 indicate a warm and humid climate in the 2 stages.These findings are consistent with the region's paleogeography and previous studies.They hold significance for sedimentologists,paleontologists,and other researchers involved in petroleum geology.
基金financially supported by the Major State Basic Research Development Program(973 Program)(Grant No.2009CB219402)
文摘Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but with strong heterogeneity. Through the analysis of trace elements, organic macerals and biomarkers, it is indicated that plankton has made little contribution to Oligocene source rocks compared with the terrestrial higher plants. The organic matter preservation depends on hydrodynamics and the redox environment, and the former is the major factor in the study area. During the sedimentary period of the Yacheng Formation, tidal flats were developed in the central uplift zone, where the hydrodynamic conditions were weak and the input of terrestrial organic matter was abundant. So the Yacheng Salient of the central uplift zone is the most favorable area for the development of source rocks, followed by the central depression zone. During the sedimentary period of the Lingshui Formation, the organic matter input was sufficient in the central depression zone due to multiple sources of sediments. The semi-enclosed environment was favorable for organic matter accumulation, so high quality source rocks could be easily formed in this area, followed by the Yacheng salient of central uplift zone. Source rocks were less developed in the northern depression zone owing to poor preservation conditions,
基金supported by the Fundamental and Commonwealth Geological Survey of Oil and Gas of China(Grant No.DD 20221662)the National Natural Science Foundation of China(NSFC)Program(Grant No.42302124).
文摘The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.
基金financially supported by the Petro China Science and Technology Major Project(Nos.2016B-0302 and 2019B-0302)。
文摘The Middle Permian Lucaogou Formation is the source rock and the main oil shale producing formation in the southeastern Junggar Basin.This study focused on the Lucaogou Formation exposed in two outcrop sections on the northern flank of the Bogda Mountain,namely the Jingjingzigou and Dalongkou sections.Here,we present integrated analysis of the sedimentology,major and trace elements,mineral components and total organic carbon contents.The paleo-environment was reconstructed including provenance,redox conditions,paleo-salinity,chemical weathering intensity and primary organic matter productivity.The results showed that the upper and lower units were deposited in distinct depositional environments with different organic matter accumulation mechanisms.The lower unit was characterized by low lake level,dry climate,fresh-brackish and well-oxygenated water.While during the deposition of the upper unit the lake level rose,climate turned wetter and the bottom water became less oxidized and much saltier.The mechanism of the organic matter accumulation is different for these two units.The preserved organic matters were mainly controlled by the primary productivity in the lower unit and by the redox conditions in the upper unit.
基金supported by the National Natural Science Foundation of China(No.41430101)the State Special Fund from Ministry of Science and Technology of China(No.2017ZX05036002)+2 种基金the Science and Technology Research Project of the Department of Education of Hubei Province(No.B2021238)the High-Level Training Program of Huanggang Normal University(No.202112004)the MOST State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan(No.MSFGPMR201902)。
文摘The beginning of the Phanerozoic was marked by abundant phytoplankton,the occurrence of animals and a newly established ecosystem structure,which in turn,resulted in different modes of organic matter(OM)cycling and preservation.In this study,we present an integrated paleontological and geochemical study of the Lower Cambrian Yanjiahe and Shuijingtuo formations in the Three Gorges area,South China.Rock samples were analyzed for major and trace elements,in order to evaluate the marine productivity.Fossil samples were recovered using palynological methods,destructive analytical techniques,SEM analysis and thin section microscopy.The organic-walled microfossils in the investigated sections include marine microphytoplankton,linings of sponge spicules,small shelly fossils and some unnamed sheet-like and net-like microfossils(animal parts).Additionally,fecal structures and coprolites fossils were found.Three intervals in the Luojiacun Section were proposed to discuss the links among microfossil assemblages and their influence on OM cycling and preservation.We found that the marine microphytoplankton was the main source of OM in the investigated sections.The appearance of fecal structures groups and massive appearance of animals in the pelagic zone indicate a higher transfer efficiency of OM aggregates through the water column.Oxygenated conditions in the water-column would have led to a moderate to low preservation of OM,an effect which would have been further enhanced by the potential presence of bioturbators.Overall,our study reveals the contribution of various organisms to the sedimentary OM and highlights the links and feedbacks among microfossil assemblages,OM recycling efficiency and OM preservation in the tipping point of the Phanerozoic“new world”.
基金supported by the National Natural Science Foundation of China(nos.41063006,41363007,and 41273099)the Science and Technology Fund of Guizhou Province(no.[2013]2296)
文摘Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.
基金financially supported by the National Natural Science Foundation of China(No.41972127)the National Key Research and Development Program of China(No.2021YFA0719000)。
文摘Nitrogen isotope compositions(δ15N)of sedimentary rocks are usually used to reconstruct the paleoenvironment and nitrogen(N)biogeochemical cycle.Theδ15N values of crude oils inherit the characteristics of relevant source rocks and can well reflect the information of hydrocarbon-forming organisms and environment in ancient water column.However,studies on theδ15N of crude oils are limited due to the low N content.In this study,a new efficient method is applied to the marine oils from the Bashituo(BST)and Halahatang(HLHT)areas of the Tarim Basin to obtain the nitrogenous components(i.e.,nonhydrocarbons and asphaltenes)for the achievement of N concentration.The carbon and nitrogen isotopes of these components and the biomarkers of oils were measured.Theδ15N values in asphaltenes(δ15NAsp)are significantly heavier than those in nonhydrocarbons(δ15NNSOs)in these oils,which are attributed to the potential directional N transfer and kinetic isotope fractionation during the thermal evolution of organic matters(OM).Theδ15NAspvalues have significant correlations with OM origin associated parameters and weak correlations with environmental parameters,suggesting that the difference inδ15NAspvalues is mainly resulted from biological source rather than redox conditions.Theδ15NNSOsvalues have a closer relationship with the redox condition than biological characteristics,indicating that they have a good response to paleoenvironmental variation in the water column,which is not completely overprinted by the difference of OM origin.Different redox conditions give rise to distinct nitrogen cycles,resulting in variousδ15N values.Anammox occurs in the water column of the Early Cambrian dominated by physically stratified conditions with significant isotope fractionation,resulting in relatively heavierδ15N of OM in the BST area.In the Middle-Late Ordovician period,the limited suboxic zone leads to an insignificant positive bias ofδ15N caused by partial denitrification in the HLHT oils.The evaluation ofδ15N in nitrogenous fractions enables a more comprehensive reconstruction of N cycle for ancient oceans.
基金supported by the National Natural Science Foundation of China(Grant Nos.92062221,42121003)Jiangxi Province Key Laboratory of Exploration and Development of Critical Mineral Resources(Grant No.GJKC2024ZZ07)+1 种基金Guizhou Provincial Science and Technology Subsidies(Grant Nos.GZ2020SIG,GZ2021SIG)Geological Exploration Fund of Guizhou Province(Grant No.2024-2)。
文摘With the global vigorous development of high-tech industries,the market demand for rare earth elements and Yttrium(REY)have experienced explosive growth.In recent years,phosphate associated REY resources(up to 18,000 ppm)found in modern deep-sea muds have attracted significant attentions.It is believed that their REY originated directly from porewater in deep-sea sediments,with a process of detrital dissolution releasing REY into the porewater.However,it remains unclear whether this model could be applied to REY-rich phosphorites from geological history,which contrasts sharply with the widely accepted Fe-oxide redox pump model at the seawater-sediment interface.Here,we present the mineralogy and REY geochemistry of clay minerals,and whole-rock Si-Fe isotopic compositions(δ^(30)Si and δ^(56)Fe)from early Cambrian REY-rich Zhijin phosphorite(∑REY,~2000 ppm)and REY-poor Meishucun phosphorite(∑REY,<400 ppm)in South China.In the Zhijin samples,illite formed around the edges of muscovite,exhibiting seawater-like REY patterns.In contrast,muscovite and orthoclase in the Meishucun samples show no contact relationship and display REY patterns typical of granite-forming minerals.The REY contents(reach 310 ppm)of muscovites from Zhijin samples are much higher than that of detrital muscovite(REY,0.09-5.86 ppm)and orthoclase(REY,2.69-6.45 ppm)from Meishucun samples.Furthermore,the data can be classified into two categories based on the correlation between δ^(30)Si values and phosphate-hosted REY enrichment in Zhijin and Meishucun samples.One is characterized by higher δ^(30)Si values(average 0.6‰)and Y/Ho ratios(average 56),and lower SiO_(2)and REY contents(average 8.10% and 1076 ppm,respectively).The other group exhibits lower δ^(30)Si values(average 0.2‰)and Y/Ho ratios(average 52),and higher SiO_(2)and REY contents(average 17.45% and 2085 ppm,respectively).In addition,compared to the Meishucun phosphorites formed in well oxidized marine environment(δ^(56)Fe,~0‰),the Zhijin phosphorites developed under fluctuating oxic-suboxic marine condition exhibit a significant negative correlation between Fe and Si isotopic compositions.These findings indicate Zhijin muscovite underwent REY exchange with seawater under fluctuating redox marine conditions,leading to REY release into the porewater and the formation of authigenic illite.This process did not occur in the Meishucun samples.It's well known that continental weathering transformed feldspar into REY-rich muscovite or illite.These REY-rich clays,transported to the seawater-sediment interface,were dissolved and released REY into the porewater within a fluctuating oxic-suboxic marine environment.We proposed for the first time that fluctuating marine redox conditions acted as a trigger for REY enrichment in ancient phosphorites,with the primary REY source being terrigenous REY-rich clay.This perspective not only provides an insight into the mechanism of REY enrichment in phosphorites,but could also account for the lack of anomalous REYenrichment in phosphorites exhibiting the precipitation of extensive pyrites if only Fe-oxide redox processes are considered.
基金was supported by National Natural Science Foundation of China (Grant Nos. 41073007 and 41273005)National Basic Research Program of China (Grant No. 2011CB808800)+3 种基金the 111 Project (Grant No. B08030)Research Fund for the Doctoral Program of Higher Education (Grant No. 20110145130001)special funding from the State Key Laboratory of Geological Processes and Mineral Resourcesa contribution to IGCP Project 572 (Grant No. GPMR201301)
文摘The change of the primary productivity across the Permian-Triassic boundary （PTB） remains controversial. In this study, records from two deep-water sections in South China （Xiakou and Xinmin sections） show the primary productivity decreased gradually from the latest Permian to the earliest Triassic, and five evolutionary stages Increase-Decrease-Recovery-Recession- Stagnation） can be observed from Clarkina changxingensis-C, deflecta to Hindeodus parvus-lsarcicella isarcica zones. Pri- mary productivity decreased abruptly from the base of C. meishanensis zone. Besides, for adjusting to the deterioration of the oceanic environment, the primary producers in the oceanic surface had changed to acritarch and cyanobacteria, which were more tolerant of stressful environment. Then the producers were under huge stagnation in the H. parvus-L isarcica zone. The values of quantitative calculation of the primary productivity from the black rock series in the Dalong Formation were very high, corresponding to that of an upwelling area in modern ocean, which shows that the strata of the Dalong Formation in the study region are potential hydrocarbon source-rocks. This result may come from the fact that South China craton was located at the equatorial upwelling area during the Permian-Triassic transitions. But organic matter contents were different in various sections because they could be affected by redox conditions and diagenesis process after burial.
基金Ministry of Mines, Government of India for financial support through grant F No. 14/77/2015Met. IV
文摘This study presents geochemical characteristics of glauconites in estuarine deposits within the Maastrichtian Lameta Formation in central India. Resting conformably over the Bagh Group, the Lameta Formation consists of ~4-5 m thick arenaceous, argillaceous and calcareous green sandstones underlying the Deccan Traps. The sandstone is friable, medium-to coarse-grained, well-sorted and thoroughly crossstratified, and contains marine fossils. Detailed petrography, spectroscopy and mineral chemistry indicates unique chemical composition of glauconite with high KO, MgO, AlOand moderate TFeO. Glauconite is formed by the replacement of K-feldspars, initially as stringers in the cleavages and fractures of feldspars. Incipient glauconite subsequently evolves fully, appearing as pellets. Fully-evolved glauconite pellets often leave tiny relics of K-feldspar. XRD exhibits characteristic peak of 10A from basal(001)reflection of glauconite, indicating the "evolved" character. The KO content of glauconites in the Lameta Formation varies from 5.51% to 8.29%, corroborating the "evolved" to "highly-evolved" maturation stage.The TFeOcontent of glauconite varies from 12.56% to 18.90%. The PASS-normalized-REE patterns of glauconite exhibit a "hat-shape" confirming the authigenic origin of glauconites. The slightly-negative to slightly-positive Ce anomaly value and the moderate TFeOcontent of glauconite agree well with a suboxic,estuarine condition. The replacement of K-feldspar by the glauconite contributes towards the high KO content. Compositional evolution of glauconites in the Lameta Formation is similar to those observed in many Precambrian sedimentary sequences.
文摘Results of Mossbauer spectroscopy and ICP-AES measurement revealed a special distribution pattern of iron species in four crossing profiles of the Tertiary Formation Type of Landslides in Japan. In comparison with host rocks, the sliding mud in the landslide slip zone contains the higher ferrous iron content and/or trace pyrite, which indicates that the forming environment was relatively reducing. The total iron content also increased with an increase in ferric iron and pyrite, in contrast, decreased with an increase in ferrous iron content. The deep-gray and black mud layers formed and accumulated in various volumes within landslide slip zones are treated as the basic criteria for the slipping activity, because the soft mud saturated with groundwater is easy to create a plastic deformation.
基金The work was supported by the China Postdoctoral Science Foundation(No.2016M591350)the National Natural Science Foundation of China(No.41202103)Sinopec Scientific and Technological Project(G5800-14-ZS-KJB158).
文摘Formation of organic-rich shale was controlled by depositional processes and environment condition.According to petrology,mineralogy,fossil composition and sedimentary structure,seven lithofacies of shale were identified in the Wufeng Formation to Longmaxi Formation,e.g.,siliceous shale,silty shale,argillaceous shale,calcareous shale,shell-bearing argillaceous limestone/calcareous mudstone,siltstonefine sandstone and bentonite.For shale in the Wufeng and Longmaxi Formations,the depositional mode was not only the suspension deposition under the low-energy hydrodynamic condition,but also the biogenic deposition,the storm deposition and the bottom current deposition indicated by large amount of siliceous biological fossils,biological detritus with size graded structure,silt laminations,lenticular bedding,ripple cross-bedding and other sedimentary structures.Trace element analysis suggested that the siliceous shale in theWufeng Formation and the lower part of Longmaxi Formation was developed in the oxygen-dysoxic/anoxic depositional environment,which was rich in organic matters;then due to influence of the sea level gradually decline and bottom current,the silty and argillaceous shales were formed,and the oxygen-dysoxic/anoxic depositional environment was destroyed,gradually leading to the worse preservation condition of organic matter.
基金We would thank Dr. WeiHua Ding for analytical assistance with the HPLC-MS equipment. This work was supported by the National Basic Research Program of China （No. 2011CB808800）, the National Natural Science Foundation of China （Grant Nos. 40930210 and 40921062） and the 111 program （B08030） in China.
文摘Isoprenoid and branched glycerol dialkyl glycerol tetraethers （GDGTs） lipids were studied in flooded and non-flooded paddy soil in Wuhan, central China, to examine the response of the GDGTs distribution to the soil flooding. Samples were collected before and after the soil flooding in four specific months. Both core （CL） and intact polar （IPL） GDGTs were quantified. Increase in the abundance of archaeol and caldarchaeol may be indicative of the occurrence of methanogens in the flooded soil. A negative correlation was observed between the ratio of IPL branched GDGT-IIa to GDGT-Ia and the soil pH. The rise of the soil pH in the acid soil is known to be controlled by the redox conditions resulting from flooding. Thus, the branched GDGTs distribution may be controlled by the water content in the paddy soil. In addition, we suggest that the anoxic conditions resulting from flooding may also control the abundance of branched GDGTs relative to crenarchaeol, which in turn results in the increase of branched and isoprenoidal tetraethers （BIT） values, the index for the terrestrial input to the marine sediments.
基金The work was supported by supported by the National Science and Technology Major Project of China(2016ZX05060)the National Natural Science Foundation of China(No.41602147,No.41702149)the China Postdoctoral Science Foundation(2017M622559).
文摘It is essential to investigate shale lithofacies distribution and controlling factor of the shale for geological evaluation of shale gas exploration and development.Through comprehensive analysis of cores,thin sections,cathode luminescence,whole-rock X-ray diffraction,element capture spectroscopy,major/trace element and other data,three major types and eight sub-type shale lithofacies in the shale of Wufeng Formation-Member 1 of Longmaxi Formation in Jiaoshiba area are identified by the three-end-member method and shale lithological classification nomenclature,and the spatiotemporal distribution law and main development controlling factors of shale lithofacies are well studied.In the Jiaoshiba area,vertically,the marine shale develops siliceous shale,mixed shale and argillaceous shale from bottom to top.Besides,lateral distribution of the shale is different from north to south;the shale lithofacies in the north area changes rapidly,the mixed shale in the north area is much thicker than that in the south area,while the siliceous shale in the south area is relatively thicker.Difference in the shale lithofacies is controlled by special sedimentary geologic events;development of the siliceous shale is controlled by the Ordovician-Silurian global volcanic event to some extent,while the mixed shale is significantly influenced by effect of bottom current,and the argillaceous shale is mainly affected by supply of terrestrial clastic material.
