Organic matter-rich fine-grained sedimentary rocks of the Permian Lucaogou Formation in the eastern part of the Junggar Basin are selected for the study, focusing on the petrological and mineralogical characteristics of the fine-grained components, and analyzing the sedimentary environments of the source rock series and its response to volcanic-hydrothermal activity. The lithological characteristics of the strata are described through observation methods such as core description and rock thin section. The organic–inorganic geochemical characteristics of the formation are reflected by TOC tests and tests of major and trace elements, and the tectonic setting and depositional environment are analyzed to explore the impact of volcanic-hydrothermal activities on the depositional environment. Lucaogou Formation is dominated by organic-rich tuffaceous shale, laminated dolomite and tuffaceous siltstone. The lake basin is located in the environment of continental island arc and active continental margin, volcanic activity occurs frequently in the area, and hydrothermal activity occurs at the bottom of the lake. The paleoclimate of Lucaogou Formation during the sedimentary period is semi-humid and semi-dry, and the lake is a strongly restricted brackish-saline lake with stable water column stratification and suboxic-anoxic environment. Volcanic activity will make the climate become dry and cold, and the climate tends to be wet with the weakening of the intensity. At the same time, it can promote the formation of anoxic environment. The hydrothermal activity at the bottom of the lake is conducive to the formation of stable chemical stratification with high salinity in the water column and the formation of anoxic bottom water environment. From the perspective of "high-quality source rock are usually affected by geological events", this paper traces the characteristics of fine-grained components and the inorganic chemical information they contain, reconstructs the paleoenvironment and explores the influence of volcanic-hydrothermal activity on it, which is of great significance for enriching the theory of terrestrial hydrocarbon source rocks.

The siliceous rock is formed by authigenic quartz and records crucial geological information on the basin's paleogeography, paleoclimate and paleotectonics. The siliceous rocks in the Lucaogou Formation are widely developed in tight oil reservoirs composed of fine-grained sedimentary rocks and occur as lamina, lenses and bands. However, there is little research on the siliceous rocks in this area, and the understanding of their formation mechanism and processes is still lacking. Two types of siliceous rocks were selected for petrological, mineralogical, in situ major, and trace, and silicon isotopic analysis to explore their source and origin. The siliceous lenses consist of anhedral microcrystalline quartz distributed in tuffaceous shales with a soft-deformation sedimentary structure, indicating a syn-depositional origin. The siliceous phenocrysts, which are composed of quartz, dolomite and smectite, are sand-sized, angular and irregular-shaped occurring in tuffaceous dolostones with a porphyritic texture and normal graded bedding suggesting an origin of the subaqueous explosion as pyroclastic flow. The siliceous lenses show positive Eu anomalies (Eu/Eu* = 1.29-1.65) and a wide range in delta 30Si values (-0.81 to -0.06 parts per thousand deviation from the NBS28 standard), indicating chemical precipitation of hydrothermal fluids. At the same time, the siliceous phenocrysts have a narrow spread in delta 30Si values (0.30-0.69 parts per thousand) with weak positive Eu anomalies (Eu/Eu* = 0.84-1.42) and weak negative Ce anomalies (Ce/Ce* = 0.87-1.02), which are interpreted as hydrothermal metasomatism. A high-pH alkaline lake environment with high temperatures and pressures brought by mantle-derived magmatic fluids are the controlling factors for the formation of siliceous rocks. The genetic model of siliceous rocks in the Lucaogou Formation provides an alternative interpretation of the origin of siliceous rocks in the study area and lays a good foundation for reconstructing the basin's paleoenvironment.

Lacustrine microcrystalline dolostones in the ancient records have been commonly interpreted as of an evaporitic origin, on the basis of their numerous occurrences in modern evaporative shallow lakes. This interpretation obscures the forming mechanisms of dolostones formed in a deep lacustrine setting, where dolostones interbedded with shale become a focus of hydrocarbon source rocks in recent years. In this study, an alternative nonevaporitic origin of dolomite is interpreted for a Permian lacustrine laminated dolostone. The dolostones are thinly intercalated with tuffaceous shales and composed mainly of volumetrically abundant, low-ordered, subhedral to euhedral, microcrystalline dolomites with a variable amount of pyroclastics. Evidence for evaporation (e.g., the presence of halite, gypsum and shrinkage cracks) and typical methanogenic microfossils is absent. Instead, our dolostones are unevenly and locally distributed as thin beds or lenses and intercalated with tuffaceous shale and have a formation temperature ranging from 31.4 to 73.8 degrees C, as estimated from dolomite clumped oxygen? isotope thermometry. In addition, the dolostones have a87Sr/86Sr 87 Sr/ 86 Sr ratio similar to that of the mantle (0.705154 on average) and extremely negative 518O 18 O (-2.9%o %o to-24%o) %o ) and positive 513C 13 C (5.1%o-10.8%o) %o -10.8 %o ) values. A lateral trend of increasing formation temperature of the dolostone toward the volcanic center correlates with the trends of: 1) an increasing amount of pyroclastics, euhedral dolomite crystals, Fe, and TOC, and an increasingly positive 5Eu value, and 2) decreasing values of 87 Sr/ 86 Sr and 518O. 18 O. The correlation suggests that a local temperature increase and frequent elemental (Fe and Mg) cycling between the conditions of dolomite supersaturation and undersaturation, which are controlled by episodic volcanic-hydrothermal activities are the causes for dolomite nucleation and growth, resulting in the formation of massive dolostone during deposition and shallow burial. The process also affected organic matter accumulation and local transformation to immature or early mature hydrocarbon during deposition and early burial. The results establish a volcanism-controlled temperature range for primary dolomite nucleation and growth, as well as hydrocarbon generation in a deep lake environment during the period of deposition and early burial, and provide insights on shale oil exploration in petroliferous rift basins.

Before Cambrian Stage 3, unambiguous body fossils of segmented bilaterians were rare, severely hampering our understanding of the early history of such important animals. Here we report a variety of microfossils with quintessential features such as paired appendages, dorsoventral and anteroposterior differentiations from the basal Cambrian Fortunian of South China, representing the earliest known three-dimensional body fossils of segmented bilaterians. These fossils were all microbial pseudomorphs built up by secondarily phosphatized bacteria aggregations, testifying microbial pseudomorph could serve as a novel and important pathway to preserve tiny, fragile bilaterian progenitors. This finding unveils a diversified segmented bilaterian world at the very beginning of Cambrian and would arouse a more comprehensive perspective on the early evolution of bilaterian body plans. ### Competing Interest Statement The authors have declared no competing interest.

The Triassic lacustrine organic-rich shale (LORS) in Member 7 of the Yanchang Formation (Carnian stage) in the southern Ordos Basin is relatively well developed. Additionally, its organic matter abundance, lake biomass and biodiversity, exceed the maximum values of the other strata deposited during the same period. Apatite is one of the most important minerals and is closely related to biological activities. However, the types and genesis of the continental sedimentary apatite and its significance to shale oil are not clear. Here, the stratigraphy, petrology, and sedimentology of the phosphorus-bearing rock series in the Ma Quan section are studied and its sedimentary environment and phosphorus formation are discussed. The current research shows that apatite in the study area can be divided into three categories: collophanite, bone fossils, and spherical microfossils. These three types of biogenic “phosphorus” products provide effective records of the transformation of the biological substances into sedimentary organic matter. There are two main formation mechanisms: the direct action of organisms and the interaction between the organisms. Bone fossils and spherical microfossils are formed by the direct action of organisms, while collophanite is formed by the indirect action of organisms. The phosphatization methods of the organisms mainly include “coating”, “replacement”, and “filling”, and the presence of a ubiquitous phosphate filler potentially reflects a sufficient phosphate supply. Apatite also is highly important for the development of organic matter in oil shale. First, it changes the productivity conditions. Second, the apatite in the shell of spherical microfossils has a certain protective effect on the organic matter in the inner cavity. In the current study, the geological processes of collophanite deposition and mineralization are explained, an important basis for prospecting phosphate resources is provided, and a new field for the study of the organic matter enrichment mechanism of source rocks is established. At the same time, the process of lake biogenic phosphorus formation provides evidence from the continental deposits in the eastern margin of the Tethys region for exploring deep global changes.

Tuffs, produced by explosive volcanic eruptions, are widely deposited throughout the Precambrian to Cenozoic stratigraphic record. Due to rapid compaction and erosion, preservation and identification of tuffs in distal environments are challenging. However, in deep lacustrine environments, tuffs may be found well-preserved as interlayers in the organic-rich mudstone. This in turn provides valuable insights into the origin, transport, and diagenesis of volcanic material. In this study, we performed an integrated sedimentological, mineralogical, and geochemical analysis of seven tuff samples collected from the lower part of the Chang7 member of the Maquan section to infer on their provenance, transport mechanisms and post-depositional alterations. Immobile element ratios, tectonic discrimination diagrams, trace element distribution patterns, and negative whole-rock εNd(t) reveal an intermediate to felsic continental arc source of the studied tuff. Supported frameworks and ash aggregates in the tuff are in favor of the transport from pyroclastic density currents and ash plumes during multiple volcanic eruptions with various degrees of eruption volume and water content. Tuff diagenesis is characterized by dissolution of plagioclase, illitization of smectite, cementation of carbonate minerals, and presence of buddingtonite. Relatively ordered illite-smectite and low vitrinite reflectance from the adjacent organic-rich mudstone indicate diagenetic evolution of studied tuff have reached mesogenetic stage.

Lacustrine dolomite nucleation commonly occurs in modern and Neogene evaporitic alkaline lakes. As a result, ancient lacustrine microcrystalline dolomite has been conventionally interpreted to be formed in evaporitic environments. This study, however, suggests a non-evaporitic origin of dolomite precipitated in a volcanic-hydrothermal lake, where hydrothermal and volcanic processes interacted. The dolomite occurs in lacustrine fine-grained sedimentary rocks in the middle Permian Lucaogou Formation in the Santanghu intracontinental rift basin, north-west China. Dolostones are composed mainly of nano-sized to micron-sized dolomite with a euhedral to subhedral shape and a low degree of cation ordering, and are interlaminated and intercalated with tuffaceous shale. Non-dolomite minerals, including quartz, alkaline feldspars, smectite and magnesite mix with the dolomite in various proportions. The Sr-87/Sr-86 ratios (0.704528 to 0.705372, average = 0.705004) and delta Mg-26 values (-0.89 to -0.24 parts per thousand, average = -0.55 parts per thousand) of dolostones are similar to those of mantle rocks, indicating that the precipitates mainly originated from fluids that migrated upward from the mantle and were subject to water-rock reactions at a great depth. The delta O-18 values (-3.1 to -22.7 parts per thousand, average = -14.0 parts per thousand) of the dolostones indicate hydrothermal influence. The trace and rare earth element concentrations suggest a saline, anoxic and volcanic-hydrothermally-influenced subaqueous environment. In this subaqueous environment of Lucaogou lake, locally high temperatures and a supply of abundant Mg2+ from a deep source induced by volcanic-hydrothermal activity formed favourable chemical conditions for direct precipitation of primary dolomite. This study's findings deepen the understanding of the origin and processes of lacustrine primary dolomite formation and provide an alternative possibility for environmental interpretations of ancient dolostones.

Pyrite, as a widely developed mineral type in shale, is of great significance in distinguishing sedimentary environments and analysing the law of shale oil and gas enrichment. Here, we take shale samples from the Chang 7-3 Member of the Triassic Yanchang Formation in the Ordos Basin as an example, use core observation, scanning electron microscope thin section identification, X-ray diffraction data analysis and other methods to analyse the macro- and microcharacteristics of pyrite, and discuss its significance in environmental indication and shale oil enrichment. The average content of pyrite in shale in the 7-3 Member of the research area is 16%, and the highest content is 50%. The core is dominated by pyrite nodules and lumps in the sedimentary period, and three types of strawberry pyrite, authigenic-semiauthigenic pyrite and heteromorphic pyrite can be observed microscopically. Different forms of pyrite were formed in different sedimentary environments: strawberry pyrite was formed in an anoxic reducing environment, and autotype-semiautotype pyrite was formed in an oxygen-poor environment. Colloidal allotype pyrite indicates that hydrothermal activity is involved in the depositional process. The pyrite content is closely related to the enrichment of shale organic matter, and the pores related to pyrite provide carriers for shale oil adsorption, preservation and migration. The anoxic sulfide environment indicated by strawberry pyrite is more conducive to the preservation of organic matter. This study systematically combines the indication of pyrite in the sedimentary environment and shale oil enrichment of upper Triassic lacustrine shale in the eastern margin of the Tethys, which provides an indication for shale oil exploration.

湖相油页岩中碳酸盐结核形成机制研究较为薄弱,因此以鄂尔多斯盆地南缘霸王庄延长组长7段油页岩中发育的巨型钙质结核为研究对象,通过野外观察、薄片鉴定和X射线衍射分析,结合结构构造、矿物组成、主微量元素以及碳、氧、锶、钕同位素特征,分析其形成条件和机理,其结果对研究与其伴生的优质泥质烃源岩的形成演化环境具有重要意义.研究认为:该结核矿物组成丰富,说明形成过程中发生了复杂的生物化学和化学沉积作用,结核中的滑石和文石矿物应为热液作用的产物;结核中方解石矿物主要有4种形态,其中钙质圆球粒应是蓝细菌鞘体矿化的产物.从结核边缘带到内、外环带及核部,主、微量元素含量差异较明显,表现出结核阶段性连续生长演化的特征.锶同位素值接近幔源锶同位素值,钕同位素值富集地幔特征,氧同位素值强烈负偏,以及高Sr、Ba含量均说明钙质结核形成时受到深部来源热液流体影响.此外结核中还发现在深湖热液环境中生存的鳕鱼的化石碎片和鱼粪化石.碳同位素值为-1.11‰～12.4‰,强烈正偏,表明碳酸盐结核的形成可能与产烷带微生物代谢活动引起的甲烷生成有关.灰岩结核成因指示该区长7油页岩生烃能力好,为优质烃源岩.

四川盆地中二叠统茅口组白云岩中蕴藏丰富的天然气资源,但是这套白云岩的成因多年来一直存在争议.盆地东部茅口组白云岩储集层多发育在茅三段中下部,纵向上厚度介于3.0～46.8m之间,平面上沿北西—南东向基底断裂呈带状展布.野外和钻井岩心观察发现,白云岩内发育交织状张性裂缝,将岩石切割呈角砾状,裂缝多被粗晶方解石、白云石充填或半充填.根据围岩和裂缝中白云石晶体形貌和产出状态,在显微镜下识别出4类不同组构的白云石:第1类为灰泥基质中"星散状"自形粉晶—细晶白云石;第2类为半自形面状组构细晶白云石,呈他形—半自形镶嵌状;第3类为具"雾心亮边"的自形晶面状组构细晶—粗晶白云石,具糖粒状结构,晶间孔隙发育;第4类为脉体充填的粗晶鞍状双晶白云石.背散射照片显示前3类白云石的"雾心"部分晶面混浊、表面分布方解石残斑及微孔,而第3类白云石的"亮边"部分与第4类鞍状粗晶白云石脉则晶体明亮、洁净、致密,属新生矿物.上述4类白云石的成分均具有富Ca和贫Fe、Mn、Sr的特点,MgO含量变化较大,其中前两类白云石MgO含量总体低于白云石标准计量,而后两类白云石的MgO含量则接近或略高于标准计量.岩石学、矿物学和地球化学特征表明:茅口组白云岩主要经历了 2期白云化作用,初次白云化作用形成第1类、第2类白云石及"雾心"白云石,二次白云化作用形成"亮边"白云石和粗晶白云石脉体;2期白云化作用均发生得很早,可能始于同沉积期至浅埋藏期.白云石原位微量元素和原位锶同位素分析表明,白云化作用流体具有混源的特点,流体可能由富Ca地下水以及与火山活动有关的热液混合而成.推测中二叠世末期峨眉山地幔柱的喷发引起四川盆地内基底断裂再次活动,造成茅口组内张性构造裂缝发育,这为白云化流体混合及运移提供了通道.

Lithotypes, organic matter, and paleoenvironment characteristics are essential attributes in organic-rich lacus-trine mudstone. Understanding the covariant relationship among them is significant not only for revealing the main controlling factors of organic matter accumulation but also for optimization of the favourable interval of unconventional petroleum resources. Herein, we present a systematic petrological and geochemical analysis of 24 samples collected from the Chang7(3) submember in the Triassic Yanchang Formation. Base on the texture, bedding, and composition of mudstone, the collected samples can be further divided into four lithotypes (Lithotype1 to Lithotype 4). Toc and rock pyrolysis data indicate that those four lithotypes mainly contain a high content of type I and II1 kerogen, good to excellent hydrocarbon generation potential, and are at the low mature to mature stage. Paleoenvir-onmental parameters, represented by paleosalinity (Sr/Ba, B/Ga), sediment provenance (Al2O3/TiO2 and Th/Sc-Zr/Sc), paleoclimate (C-value, Sr/Cu), paleoproductivity (P/Al, P/Ti, Ni/Al, Ni/Ti, Cu/Al, and Cu/Ti), bottom-water redox conditions (V/Cr, V/(V + Ni), and U-EF-Mo-EF), and sedimentation rate ((La/Yb)(N)), indicate that the four lithotypes were all deposited in freshwater environments and sourced from felsic volcanic rocks but different in the paleoclimate, paleoproductivity, bottom-water redox conditions, and sedimentation rate. Ac-cording to the ratios of C-value, B/Ga, Al2O3/TiO2, P/Ti V/Cr and (La/Yb)(N) with TOC, The degree of organic matter accumulation is positively correlated with the humidity of the paleoclimate, paleoproductivity, and reducibility of bottom water but negatively related to the sedimentation rate. Comparing the differences between the organic matter characteristics and paleoenvironment of the four lithotypes, we conclude that Lithotype1 is the most favourable target lithotype for developing unconventional oil resources.

The coupling relationship between volcanic-hydrothermal activities and hydrocarbon generation has been a common understanding in recent years. However, there is a lack of theoretical and practical guidance in the application hydrocarbon production. The fine-grained sedimentary rocks of the middle Permian Lucaogou Formation in the Jimsar Sag in the Junggar Basin, NW China, are critical source rocks and have been simplify regarded as a mudrocks for target for tight oil exploration. Recently studies show that rocks were deposited in an intracontinental lacustrine environment with multiple volcanic-hydrothermal activities. Their complex micro-scale lithological characteristics restrict the understanding and further exploration and development of tight oil. Hence, this study focuses on the detailed lithological and their organic geochemical characteristics of the Lucaogou Formation using microscopic thin-section observation, scanning electron microscopy, X-ray diffraction, Rock-Eval, saturated hydrocarbon chromatography and mass spectrometry. The following key conclusions were obtained. First, the massive mudrocks are sub-divided into lithofacies for hydrocarbon generation, including tuffaceous shale, calcareous shale and dolomitic shale, and, microinterval reservoirs, including dolostone and sedimentary tuff. Second, the origins of organic matter in Lucaogou Formation were mainly plankton, bacteria with minor of land plants. The depositional environment is high salinity and anoxic conditions. Materials derived from volcanic-hydrothermal activities, lacustrine precipitation, and terrestrial transportation mixed with various proportions to form this formation. Third, a mixture of carbonate minerals, felsic minerals and clay minerals is the best source rock, and the higher the mixture, the better. This research not only provides insight into the influence of volcanic-hydrothermal activities on lithology and organic matter enrichment, but also providing a potential scheme for the tight oil exploration and development in similar rifted geological settings.

Sediments originated from volcanic-hydrothermal activities show clear relationship with hydrocarbon generation and accumulation in fine-grained sedimentary rocks at a regional scale. However, the fundamental processes and mechanisms of this relationship are still poorly understood at a microscopic scale to hamper efficient hydro-carbon exploration. In addition, coarse grains common in volcanic lacustrine fine-grained sediments have been traditionally interpreted as diagenetic products during early and late burial. Our study, however, suggests that coarse calcite grains are not diagenetic, but formed by subaqueous explosion. The calcite grains occur in lacus-trine fine-grained sedimentary rocks in the middle Permian Lucaogou Formation in the Santanghu intracontinental rift basin, NW China. They are sand sized, angular, mono-and polycrystalline, and discretely scatter in silt to clay-sized non-calcite pyroclastic matrix. The calcite grains and the mud matrix are interpreted as a pyroclastic debris flow deposit. In-situ Sr-87/Sr-86 ratios (0.704932-0.705840, and 0.705137 on average) of the calcite grains are similar to those of mantle rocks, indicating an origin closely related to mantle-derived fluids. The in-situ C-613 values (4.24 parts per thousand to 5.06 parts per thousand , and 4.57 parts per thousand on average) and extremly negative 618O values (-21.70 parts per thousand to -21.18 parts per thousand , and - 21.49 parts per thousand on average) indicate that extensive hydrothermal alteration and microbial activities influenced the formation of the calcite. Element composition and homogenizaiton temperature of fluid incusions of calcite and biomarkers of the mudstone all suggest a relatively low-temperature hydrothermal condition in a saline and reducing environment. Furthermore, hydrocarbon-rich inclusions are rich in the calcite grains and have two modes of occurrence and maturity. They indicate that the organic matter was generated from algae bloom, which was caused by volcanic-hydrothermal activities. Alternatively, the hydrocarbon may have an inorganic origin originated from a mantle source. Our findings provide an alternative interpretation on the origin of coarse calcite grains in fine-grained sedimentary rocks and demonstrate a microscopic relationship between volcanic-hydrothermal activities and hydrocarbon generation and accumulation in a tectonic active rift basin.(c) 2022 Elsevier B.V. All rights reserved.

The Permian mafic dykes of Santanghu Basin offer an opportunity to study the nature of mantle source and tectonic setting of the basin, as well as to provide the theoretical basis for structural transformation of East Junggar region. In this study, zircon U–Pb geochronology, mineral composition analysis, whole‐rock elemental, and Sr‐Nd isotopic geochemistry were conducted to explore the origin and evolution of the primitive magma. LA‐ICPMS zircon U–Pb dating yields ages at 269 Ma. The elemental geochemistry results suggest enrichments in Ba, Pb, and Sr but depletions in Nb, Ta, Zr, and Hf, which indicate that the magma source was influenced by fluid metasomatism. All samples show moderate initial Sr‐Nd isotope results ((87Sr/86Sr)I = 0.704299 to 0.704490 and εNd(t) = +6.16 to +6.83) and have high Sm/Yb ratios, which suggest that the diabases were derived from partial melting of 5%–7% spinel‐garnet Iherzolite lithospheric mantle. Combined with petrological, geochronological data, and the regional tectonic background, it is interpreted that the diabases from Santanghu Basin originated from lithospheric mantle metasomatized by subduction fluids under the background of intracontinental extension.

The Ordos Basin is a large depression-type lake basin in the late Triassic. Here, we present a study on Yufenites, which were found in the BWZ (BaWangZhuang) section, TNH (TangNiHe) section and Well Z11 in the Tongchuan area on the southern margin of the basin and in the lower shale layer of Chang 7 member in Triassic Yanchang Formation. Yufenites are slightly flattened spindle-shaped fossils, pointed and thin, with obvious spiral patterns on the surface. The spiral starts from the thin part and turns from right to left, and the pitch changes from narrow to wide. The Yufenites contains animal and plant residues that have not been completely digested, and a large number of mineral aggregates that formed around phosphorus-containing dolomite as a growth base. Yufenites had a high viscosity and strength when discharged. Due to the action of microorganisms, the diagenesis of Yufenites occurs earlier and faster than that of the surrounding rocks. Based on this description, we believe that this Yufenites is from a large carnivorous fish. In the Late Triassic, humid and hot climatic conditions, low water kinetic energy, desalinated water, high productivity, magmatic-hydrothermal activity and other factors played an important role in the preservation of Yufenites.

The biostratigraphic information from the last remnants of the Tethys Seaway in northern Pakistan was used to date the cessation of marine sedimentation as a result of the closure of the eastern Tethys Seaway and to give a minimum time for the India-Asia collision. The current detailed biostratigraphic investigations of the Eocene Kohat Formation in the Kohat Basin divulged that the rock unit in the study area contains age-diagnostic larger benthic foraminiferal (LBF) species of middle Eocene age. Based on the association of identified LBF species, two local biozones,i.e.PKBZ 1 and PKBZ 2, are documented and are comparable with published SBZ 13 and SBZ 14 zones, suggesting an early to middle Lutetian age of the rock unit. The integration of current biostratigraphic information of the Kohat Basin with detailed literature on other basins suggests that the closure of the eastern Tethys Seaway in Pakistan occurred in four stages: (i) closure of the northwestern Kohat region during the early Ypresian (55.9-55 Ma), (ii) followed by the closure in the Potwar region, apart from its northwestern domain, during the middle to late Ypresian (54-49.9 Ma), (iii) closure of the Tethys Seaway in the Hazara-Kashmir and northwestern Potwar regions during the early Lutetian (49-45.8 Ma) and (iv) the final stage of Tethys closure has occurred in the Kohat region during the middle Lutetian 1 (45.8-43.6 Ma). The biostratigraphic information in the current study suggests that the final stage of eastern Tethys closure in northern Pakistan occurred at 45.8-43.6 Ma, and thus it gives a minimum age for the India-Asia collision. Such diachroneity can be observed elsewhere in the eastern Tethys, including Iran, Nepal, Bangladesh, Turkey and Tibet. The closure started first in eastern Tethys, continued in both eastern and western Tethys, and was finally completed in eastern Tethys.

Knowledge about movable fluid behavior's underlying mechanisms is crucial to hydrocarbon development in tight sandstones. In this study, multi-techniques were used to determine mineralogy, pore structures, and movable fluid properties. Whether the connectivity of pore networks optimizes, deteriorates, or has no influence on the fluid flowability has been disputed. During the research, both abundant illite and little chlorite contribute to improved flowability since a large pore-throat radius corresponds to enough accommodation space. Also, the pore-throat connectivity and apparent contact angle fluctuate because of the change of pore size range. The movable fluid properties are primarily dependent on the degree of throat development, while the well-connected pore networks, especially enough void space, correspond to good reservoir quality. In this study, the micro-mechanism of pore size distribution was disclosed by multi-techniques, and the governing factors of reservoir qualities for tight sandstones were defined.

准噶尔盆地东部的红柳峡地区位于卡拉麦里断裂以南,是探讨准噶尔盆地是否存在前寒武纪基底问题的代表性地区之一,因此针对该区中元古代札曼苏岩群中的浅变质碎屑岩,进行了锆石LA-ICP-MS U-Pb定年研究.研究结果表明,测定的110颗碎屑锆石的年龄分布范围为409±8 Ma至1387±54 Ma,具有多峰的分布特征,其中碎屑锆石的年龄主要集中在409 ～ 516 Ma,其主峰为462 ～ 488 Ma,次要的峰为433 ～ 460 Ma、490 ～516 Ma和409 ～ 425 Ma,并有4粒碎屑锆石年龄介于742～1387 Ma之间.研究认为,该沉积岩的形成时代不是中元古代而是泥盆纪;综合该区的变质玄武岩和辉长岩锆石同位素定年数据,认为札曼苏岩群形成时期的下限不早于早泥盆世.其古老锆石年龄数据结合区域综合对比分析得出,沉积物源区——准噶尔盆地东部可能存在前寒武纪结晶基底的重要信息.

Large depression-type lake basins developed during the Late Triassic in the Ordos Basin, and hydrothermal activity at the bottom of these lakes was frequent. Here, we report an example from the Chang 7 hydrothermal deposition area of the Triassic Yanchang Formation in the Ordos Basin, China: Yanchanglepis Tongchuanlepis gen. et sp. nov. Its general morphological characteristics include a long spindle-shaped body, a long dorsal fin base, a rear-facing gap between the ventral fin and anal fins, thick fins, small decorative spine scales, inclined hanging bones, high gillcap bones, small scales and a number of horizontal scales. Its unique composition, morphology and distribution characteristics have become the key to exploring the habitat of organisms living in extreme environments. This discovery provides a fossil record of cod evolution in Late Triassic continental sedimentary basins. The study is expected to provide insights into the life forms of various extreme organisms in hydrothermal environments and further our understanding of nutrient cycling and ecosystem evolution in deep lakes.

陆内湖相烃源岩系是中国含油气盆地广泛发育的一类组分复杂且富含有机质的细粒沉积岩.随着非常规油气资源需求量日益增加,该岩系被作为致密油或页岩油层系受到广泛关注.然而,其极细的粒度增加了精细岩石学、矿物学研究难度,使它长期被简单视为陆源沉积岩.研究发现,该岩系中发育丰富的火山喷发及热液喷流产生的深源物质,并与油气的生成和富集表现出了极强的耦合关系.因此,探索深源物质如何参与烃源岩形成并影响油气生成亟待深入研究.作者详细总结并探讨了国内外近年来关于湖相烃源岩成因以及火山—热液活动带来的深源物质与油气形成关系的现阶段新发现与认识.并结合笔者研究团队基于新疆三塘湖盆地二叠系芦草沟组烃源岩的新发现,采用精细的岩石学、矿物学方法,结合无机和有机地球化学等方法,初步开展了该耦合关系的机理研究.认为火山—热液深源物质参与了烃源岩的沉积与成岩作用,并与正常湖相沉积物共同影响着油气的形成.建议重新认识湖相烃源岩的物质组成,从而拓展陆相生油理论,同时为同类型非常规油气资源勘探开发提供理论指导.