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摘要:A new species of Bothriolepis (Placodermi, Antiarcha), B. zhujiangyuanensis sp. nov., is described from the Eifelian (Middle Devonian) Shangshuanghe Formation at the Pearl River Source Scenic Area, Qujing, Yunnan Province, southwestern China and is characterized by a broad postpineal plate bearing a straight anterior margin, a premedian plate wider than long, and a weakly developed dorsal median ridge of the trunk shield. As the eighth Bothriolepis taxon in China, B. zhujiangyuanensis sp. nov. provides a wealth of morphological data to clarify the intrageneric interrelationships. Maximum parsimony analysis, using a revised data set of the genus with 76 ingroup taxa and 72 characters, yields a well-resolved consensus tree for Bothriolepis. The phylogenetic result shows a sister-group relationship between B. zhujiangyuanensis and B. babichevi from Kazakhstan, corroborating the biogeographic proximity between the South China and Kazakhstania blocks during the Middle Devonian.

摘要:The Upper Cretaceous successions of Wadi Umm-Khayshar, southern Galala Plateau, North Eastern Desert, Egypt, are composed of highly diversified faunas and subdivided from base to top into the Galala (Middle–Late Cenomanian), Maghra El Hadida (Latest Cenomanian–Late Turonian), Matulla (Coniacian–Santonian), and Sudr (Campanian–Maastrichtian) formations. Five ammonite biozones are recorded in the studied section: Neolobites vibrayeanus, Vascoceras cauvini (late Cenomanian), Vascoceras proprium, Choffaticeras segne, and Coilopoceras requienianum (Turonian) zones. The paleoenvironments of the Upper Cretaceous succession are interpreted based on detailed study and microfacies analysis that reflect a deposition in a homoclinal ramp platform ranging from intertidal to deep subtidal. The paleoecology of the Cenomanian–Turonian succession in the studied section is explained based on a detailed study of macrofaunal associations and sedimentary facies. Quantitative analysis (Q-mode cluster analysis, using the Raup–Crick Paired group method) of 1029 macrobenthic specimens, including 45 species of mollusks and echinoids yielded five macrofaunal associations (A–E) that are described and interpreted as remnants of communities. The nektonic elements are represented by 235 cephalopod specimens of 20 species; heatmap cluster analyses show the distribution of these specimens during the Upper Cenomanian–Turonian stages. Environmental parameters (substrate consistency, rate of sedimentation, water energy, surface-water productivity, and oxygen availability) controlled the distribution of the studied macrofauna. The five associations are divided into two major groups: low-stress associations (A, B, C, and D), and a high-stress association (E). The low stress associations are recorded from two different habitats: (1) a high-energy, firm substrate habitat, dominated by epifaunal bivalves, large epifaunal gastropods and a regular echinoid; (2) a low-energy, soft substrate habitat dominated by infaunal bivalves and echinoids. The high stress association is dominated by only two species and recorded from a high-energy shoal environment during a regression phase. A detailed study of macrobenthos and cephalopods provides a good paleoecological understanding of Cenomanian–Turonian succession in the Wadi Umm–Khayshar section.

摘要:The Southwest Tianshan is the suture zone between the Central Tianshan and the Tarim Craton. To better illustrate the subduction polarity of the Southwest Tianshan Ocean, a systematic detrital zircon LA-ICP-MS U-Pb geochronology of sedimentary rocks of the Devonian Apadaerkang Formation and the Carboniferous Akeqiayi Group of the Biedieli area in the Wushi region is the focus. Detrital zircon ages indicate that the youngest grains of the targeted quartz sandstones are Late Devonian and Early Carboniferous in age, respectively. These ages also have relatively similar age spectra, indicating a similar tectonic setting and source in the Biedieli area during the Devonian to Carboniferous. The main spectrum peaks occur at 2360, 1960, 810, 640 and 440 Ma, with a principal age peak in the early Paleozoic (474–430 Ma), and the Central Tianshan Terrane is indicated as the main source. The detrital zircon geochronology and sedimentary characteristics of the Biedieli rocks indicate that the Paleozoic sedimentary rocks in the northern Wushi region were formed at an active continental margin, associated mainly with the early Paleozoic subduction of the South Tianshan Ocean.

摘要:Deciphering high-pressure granulite-facies metamorphism and anatexis within a collisional orogeny can provide crucial constraints on geodynamic evolution and melt activity during subduction and exhumation. Combining petrographic observations, mineral chemistry, REE in Grt-Cpx thermobarometry, and previous work, at least four stages are suggested for the metamorphic evolution of the mafic granulites in the South Altun, including the protolith stage, the high-pressure granulite-facies stage (909–1037°C and 17.3–30 kbar), medium-pressure granulite-facies overprint (9.1–11.9 kbar and 753–816°C), and subsequent late amphibolite-greenschist-facies metamorphism. Zircon U-Pb dating shows that the mafic granulites underwent high-pressure granulite-facies metamorphism at 497.2 ± 3.7 Ma, while the leucosome formed at 498.2 ± 2.9 Ma. Thus, the leucosomes from the host mafic granulite may have been formed at the high-pressure granulite-facies metamorphic event. The characteristics of zircon morphology, mineral inclusions, low Th/U values, HREE enrichment, and negative Eu anomalies indicate that these zircons from the leucosome were formed from the metamorphic melts. The characteristics of whole-rock major and trace elements as well as Hf isotopic features of zircons between the leucosomes and the host mafic granulite indicate that the melt may have been generated by the partial melting of the host mafic granulite.

摘要:The Yishui complex, located in the western Shandong area of the North China Craton, is representative of the Archean crystalline basement of the North China Craton to explore the early tectonic-thermal evolution history of the Earth. Detailed petrography, mineral chemistry, metamorphic evolution and zircon U-Pb dating are presented for felsic granulite and two-pyroxene granulite from the Yishui complex to contribute to new insights into the Neoarchean tectonic evolution of the North China Craton. Three mineral assemblages are recognized for these granulite samples, including the prograde (M1), peak (M2) and retrograde (M3) mineral assemblages. Conventional geothermobarometry and phase equilibrium modeling yield P-T conditions of 6.5–10.9 kbar/718–839°C for the peak metamorphism, which define a medium-pressure granulite-facies metamorphism occurred at middle to lower crust. Anticlockwise P-T paths with near-isobaric cooling (IBC) retrograde segments were reconstructed. Zircon LA-ICP-MS U-Pb dating suggests that the protolith of the felsic granulite was emplaced at 2541 ± 7 Ma and the subsequent medium-pressure granulite-facies metamorphism occurred at 2518–2494 Ma. A two-stage mantle plume related crustal-scale sagduction geodynamic regime is proposed in the western Shandong terrane in the Neoarchean.

摘要:We report new SHRIMP zircon U-Pb ages, zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia, China. In combination with published geochronological and geochemical data, the granitoids in the region can be divided into two age groups: ca. 285 Ma and ca. 269 Ma. The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline, weakly peraluminous I-type granodiorites with εHf(t) values of ?19.6 to ?4.3, which demonstrates evidence of crustal reworking; the granitoids of the second group, however, mainly consist of A-type granites that are high-K calc-alkaline to shoshonite, metaluminous to weakly peraluminous, and have high 10,000 × Ga/Al ratios (2.59–3.12) and εHf(t) values ranging from ?11.3 to ?2.7, all of which demonstrates a mixed crust-mantle source. We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.

摘要:The petrogenesis and genetic link to polymetallic mineralization of the granites in the Dayishan complex, southern Hunan province remain debated. Here, we present an integrated study on the petrology, zircon U-Pb ages and whole-rock geochemistry for this complex. Our findings indicate that the southern complex consists of (amphibole-bearing) biotite granites and muscovite granites emplaced at 153–151 Ma, and the central and northern complex consists of two-mica granites and tourmaline-bearing muscovite granites, respectively with the former emplaced at 164 Ma and the latter at 150 Ma. The (amphibole-bearing) biotite granites have SiO2 contents of 68.0–73.8 wt% and are enriched in alkalis and rare earth elements and depleted in Sr and Ba. They display Zr + Y + Ce + Nb > 350 ppm and 10000 × Ga/Al > 2.6 along with high zircon saturation temperatures (821–883oC). The two-mica granites and (tourmaline-bearing) muscovite granites have high SiO2 (74.4–77.3 wt%) and low Ga/Al, Zr + Nb + Ce + Y, K/Rb, Zr/Hf, and Nb/Ta along with low zircon saturation temperatures (709–817oC). Geochemical characteristics suggest that the (amphibole-bearing) biotite granites are A-type granites generated through shallow dehydration melting of early Paleozoic granitoids, and that the two-mica granites and (tourmaline-bearing) muscovite granites are fractionated A-type granites produced through fractionation crystallization from the (amphibole-bearing) biotite granites accompanied by fluid fractionation.

摘要:The 7 ka old Qixiangzhan lava flow (QXZ, Tianchi volcano) represents the last eruptive event before the 946 CE, caldera-forming ‘Millennium’ eruption (ME). Petrographic, whole rock, mineral composition, Sr-Nd isotopic data on QXZ show that: (a) the lava consists of two components, constituted by comenditic obsidian fragments immersed in a continuous, aphanitic component; (b) both components have the same geochemical and isotopic variations of the ME magma. The QXZ and ME comendites result from fractional crystallization and crustal assimilation processes. The temperature of the QXZ magma was about 790°C and the depth of the magma reservoir around 7 km, the same values as estimated for ME. QXZ had a viscosity of 105.5–109 Pa s and a velocity of 3–10 km/yr. The emplacement time was 0.5–1.6 yr and the flow rate 0.48–1.50 m3/s. These values lie within the range estimated for other rhyolitic flows worldwide. The QXZ lava originated through a mixed explosive–effusive activity with the obsidian resulting from the ascent of undercooling, degassing and the fragmentation of magma along the conduit walls, whereas the aphanitic component testifies to the less undercooled and segregated flow at the center of the conduit. The QXZ lava demonstrates the extensive history of the ME magma chamber.

摘要:The temporal and spatial evolution of the Ailao Shan–Red River (ASRR) fault zone, which serves as an important accommodation zone for the extrusion and escape of the Southeastern Tibetan Plateau, is crucial for analyzing the uplift and growth of the plateau. Based on the petrology and apatite fission track analysis, the tectonic history and active pattern of the ASRR fault zone since the middle Miocene are determined in this study. The ASRR fault zone exhibits 12–8 Ma and 8–4 Ma rapid cooling phases since the middle Miocene. The 12–8 Ma and 8–4 Ma cooling may imply that the dextral movement of the ASRR fault zone presents a migration trend from northwest to southeast, accompanied by the weakening of the activity intensity, which is directly related to deformation processes, including extrusion boundary migration and active tectonic movements of the southeastern Tibetan Plateau, since the middle–late Miocene.

摘要:The formation of Mesozoic natural gas in the Pengyang area of southwestern Ordos Basin is discussed, from the perspective of microbial community characteristics, in order to clarify the relationship between the origin of natural gas and its associated indigenous microbial community. The types and diversity of indigenous microbial communities associated with the oil reservoir were studied by means of collecting reservoir formation water samples from exploration wells. The indigenous microbial communities in the Chang 8 member of the Yanchang Formation were primarily distributed within Proteobacteria and Firmicutes, including the specific species and genera of Methylobacter, Pseudomonas, Haibacter, Toxobacillus, Acinetobacter and Adura actinomyces. The results of diversity analysis shows that the number of common genes was 5448, while the number of unique genes and information was less. This reflects the fact that the strata in the study area are relatively closed and not invaded by external water sources, which leads to the development of biological community diversity. In conjunction with the analysis of geochemical characteristics of oil and gas reservoirs in this area, this indicates that the study area possesses the necessary geological conditions for microbial degradation. It is the first time that the species and diversity of the indigenous microbial community in the Ordos Basin have been analyzed, showing that microbial degradation is the main cause of natural gas formation here, changes the characteristics of crude oil in this area and provides first-hand information on the impact of indigenous microorganisms on the reservoir.

摘要:This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin. It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development. The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite, while those from intermediate rock denudation can be dissolved or transformed into illite. Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components. Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain, with a closed original geochemical systems, have been in the oxidizing environment for a long time. The tuffaceous matrices mainly transforms into hematite or illite. These minerals occupy the primary pores and are difficult to dissolve by felsic fluids, which inhibits the development of high-quality reservoirs. The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system. The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle’s compaction resistance, but also can be fully dissolved, which promotes the formation of high-quality reservoirs.

摘要:Controlled by fluctuating paleoclimates and sedimentary environments, the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile, challenging conventional geological interpretation. To elucidate the possible influence of heterogeneity on resource evaluation, a high-resolution sampling approach was applied to an 86.2 cm long core from the Lucaogou Formation of the Jimsar sag in the Junggar Basin. 86 sets of samples were micro-drilled from the core and subjected to comparative Rock-Eval pyrolysis. Following the classical guidelines, the organic abundance, kerogen type, and maturity of source rocks were exhaustively analyzed. Experimental results revealed that organic richness and composition vary significantly under different sedimentary backgrounds, which in turn leads to differential hydrocarbon generation. The combination of hydrocarbon generation, transport, and expulsion results in peculiar patterns for hydrocarbon accumulation in the Lucaogou Formation. Laminated shales in the Lucaogou Formation serve as both hydrocarbon source rocks and reservoirs, with laminae being migration pathways. Organic-rich dolomites in the Lucaogou Formation have a considerable hydrocarbon-generating capacity and present the characteristics of self-generation and self-storage. However, massive mudstones act purely as hydrocarbon source rocks.

摘要:Coal pore parameters are closely related to macrolithotypes and coal structures, having a large influence over the gas potential and productivity of coalbed methane (CBM). The Middle Jurassic Xishanyao Formation, located in the southern Junggar Basin of northwestern China, has geological conditions with rich CBM resources. The 46 Xishanyao coal samples gathered from the drilling cores and coal mines cover 4 types of macrolithotypes (bright coal 1, semi-bright coal 2, semi-dull coal 3, and dull coal 4) and 2 types of coal structures (primary coal I and cataclastic coal II). Based on a range of pore testing experiments and analytical methods, the dual effects of different macrolithotypes and coal structures on pore structures were intensely studied. The results showed that the specific surface area (SSA) and total pore volume (TPV) of coal samples increased gradually from bright to dull coals. For the same macrolithotypes, the SSA and TPV of the primary coals were lower than those of the cataclastic coals. Generally, the pore structures of bright and semi-bright coals are simpler when compared to semi-dull and dull coals with the same coal structure, whereas cataclastic coals have more complicated pore structure systems than primary coals with the same macrolithotypes. The bright and semi-bright coals have higher vitrinite contents and more endogenous fractures, whereas well-developed structural fractures were identified in cataclastic coals. Therefore, bright and semi-bright coals have better pore connectivity than semi-dull and dull coals with the same coal structure, the pore connectivity of cataclastic coals being slightly better than that of primary coals under the same macrolithotypes. In terms of the CBM adsorption conditions, the eight type samples formed a descending order: II-4 > I-4 > II-3 > I-3 > II-2 > I-2 > II-1 > I-1, while they ranked as follows when consideration was given to the CBM seepage capacities: II-2 > II-1 > I-2 > I-1 > I-3 > I-4 > II-3 > II-4. As a result, it could be determined that the bright and semi-bright coals had stronger adsorption capacities, whereas the cataclastic coals had better pore connectivity and seepage capacities. Pore structure characteristics should be analysed under the dual control of different macrolithotypes and coal structures, so that they can provide greater value for guiding CBM exploration and exploitation, as along for preventing underground gas accidents.

摘要:It is of great significance for deep oil and gas exploration to understand the origin and evolution behind overpressure. Overpressure occurs in the deep Shahezi Formation of Xujiaweizi fault depression. However, due to limited degree of exploration, there are some problems in the study area, such as unclear understanding of the origin of overpressure and the vague investigation of overpressure evolution. To clarify the impact of overpressure on oil and gas migration and accumulation in the study area, this study focuses on the research of the origin and evolution of overpressure in the Shahezi Formation of the study area, utilizing single well logging parameters and combining methods such as microthermometry of fluid inclusions, laser Raman spectrum, and basin simulation. The results show that the overpressure of the Shahezi Formation in Xujiaweizi fault depression is primarily generated by hydrocarbon generation pressurization, and the evolution of overpressure is closely related to hydrocarbon generation. The development of overpressure can be divided into two evolutionary stages: early hydrocarbon generation pressurization and late uplift release, with slight variations in different regions. Tight glutenite gas reservoirs in the Shahezi Formation are characterized by continuous charging. The overall charging period ranges from the late Denglouku to the early Mingshui (110–67 Ma ago). There is an obvious paleo-overpressure during the gas reservoir formation period. The gas generation period of source rocks occurred approximately 125–60 Ma ago, and the main gas generation period (112–67 Ma ago) highly coincides with the period of natural gas charging. The anomalously high pressure during the accumulation period is considered the significant driving force for natural gas charging. In addition, the sustained effect of overpressure provides better conditions for the preservation of tight gas reservoirs within the source. The results of the study are of guiding significance for the in-depth exploration and development of deep tight sandstone gas in the Shahezi Formation of Xujiaweizi fault depression.

摘要:Burial dissolution is a critical diagenetic process influencing ultra-deep carbonate reservoir development and preservation. Artificial carbonate samples with different internal structures were prepared, and high-temperature and high-pressure dissolution kinetic simulations were conducted. The results demonstrate that the intensity of burial dissolution is controlled by temperature and pressure, while tectonic-fluid activity influences the development pattern of burial dissolution, ultimately determining the direction of its differential modification. Extensive burial dissolution is likely to occur primarily at relatively shallow depths, significantly influencing reservoir formation, preservation, modification, and adjustment. The development of faults facilitates the maintenance of the intensity of burial dissolution. The maximum intensity of burial dissolution occurs at the tips and overlap zones of faults and intersections of multiple faults. The larger the scale of the faults, the more conducive it is to the development of burial dissolution. Burial dissolution fosters the formation of fault networks characterized by enhanced reservoir capacity and permeability. Burial dissolution controlled by episodic tectonic-fluid activity is a plausible explanation for forming the Tarim Basin’s ultra-deep fault-controlled “string-bead-like” reservoirs.

摘要:Large basins are currently the global focus for geothermal development, with their hydrothermal system being controlled by a variety of factors, such as basement relief and fracture development. Donglihu is located at the north of the Cangxian uplift in the North China Basin, the concentrated geothermal resource development zone in North China. This study systematically collects temperature logging data and long-term dynamic monitoring of water level and water quality as well as group well tracer test data carried out in this area in recent years, on the basis of which the hydrothermal controlling role of the deep hidden faults is systematically analyzed. The results show that the Cangdong fault communicates with different geothermal reservoirs in the shallow part and plays a specific role in the water-heat channel of the local area. As a result, the high-value area of the geothermal temperature gradient in the sedimentary layer of the Donglihu area is distributed around the Cangdong fault. The geothermal reservoir temperature of the Minghuazhen Formation within the influence of the fault is also significantly higher than the regional average, the hydraulic head of different geothermal reservoirs showing a consistent and synergistic trend. However, the water quality has been stable for many years without any apparent changes. This understanding has a particular significance for further deepening understanding of the geothermal genesis mechanism in sedimentary basins and guiding future geothermal exploration and development in the Donglihu area.

摘要:Black soil is essential for maintaining regional food security and promoting global agricultural production. Understanding the weathering process of parent material and the accumulation of organic carbon is crucial to comprehending the developmental history and future trends of black soil, especially against the background of large-scale global cultivation and climate change. Although the importance of black soil formation and evolution cannot be ignored, the relevant research is still very scarce. In this study, a typical eight-meter-deep soil core was collected from the Keshan area of the Songnen Plain, Northeast China, where surface black soil developed on paleo-sediments. Using 14C dating, the formation age of the black soil was determined. Based on the characteristics of the geochemical composition, grain size and the magnetic susceptibility of the sediments, it was demonstrated that the black soil and its parent material originated from reworked loess. Furthermore, the mass transfer coefficient (τ) of some elements was determined, in order to explore the soil weathering process. By calculating the transported amount of alkaline and alkaline-earth elements, the weathering rate of parent material to black soil was found to be weak, at 0.16 kEq·ha?1·year?1. Combining the results of dating and carbon density in the different layers of black soil, the accumulation rate of organic carbon was determined as follows: rapidly increasing in the initial period of 13.2–2.2 ka, reaching its maximum average value of 34.0 g·cm?2·a?1 at 2.2–0.8 ka, then showing a decreasing trend with an average value of ?77.5 g·cm?2·a?1. Compared with regional climate change, Keshan black soil has developed under a colder and wetter climate during the Holocene. Predictably, ongoing global warming may lead to the degradation of black soils in the Songnen Plain, as well as in other regions. Our results will enrich geological knowledge of black soil formation and future evolutionary trends.

摘要:The water conductivity of karst collapsed column is affected by multiple factors such as the characteristics of its own column filling, structure and mining disturbance. As a structural water-conducting channel, fault usually plays a controlling role in hydrogeological structure. During the process of mine water hazard prevention and control, it was discovered that the lithology composition, compaction and cementation degree and water physical properties of karst collapsed column fillings were all non-conducting water, but due to the influence of combined development faults, some exploration drill holes showed concentrated water outflow. Based on this, the scientific hypothesis was proposed that fault cutting leads to water conduction in karst collapsed columns. The study comprehensively used methods like chronology, exploration data analysis, and hydrochemical testing to analyze the chronological relationship between faults and karst collapsed columns, their spatial relationship, outlet point distribution and water chemical properties, and the impact of faults on the water-conductivity of karst collapsed columns, which proved the effect of fault cutting on changing water conductivity of karst collapsed column. The research showed that later fault cutting through karst collapsed columns turned the originally non-conductive karst collapsed columns into water-conductive collapsed columns at the fault plane, creating a longitudinally connected water-conducting channel. A new model of fault cutting karst collapsed column to change the original water conductivity of karst collapsed column was proposed. The research results can provide a theoretical basis for the prediction of the water conductivity of the karst collapsed column. According to whether the karst collapsed column was cut by the fault, it was predicted theoretically, so as to determine the key areas of water conductivity detection and prevention and control, and has broad application prospects under the background of source control of mine water disaster.

摘要:As one of the most serious geological disasters in deep underground engineering, rockburst has caused a large number of casualties. However, because of the complex relationship between the inducing factors and rockburst intensity, the problem of rockburst intensity prediction has not been well solved until now. In this study.

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