Abstract:The natural gas hydrates-bearing shaly silt reservoirs are considered to be the most difficult target in exploitation. The first trial production test of the gas hydrate in the South China Sea conducted in 2017 proved that the reservoir is exploitable. On the basis of the understanding of the previous trial production, optimization and fine description of hydrate deposits, numerical simulation and onshore tests, the second gas hydrate trial production test were carried out by the China Geological Survey in the Shenhu sea area of the South China Sea from October 2019 to April 2020. This trial production overcame a series of technical problems, such as well head stability, horizontal well drilling, reservoir stimulating and sand controlling and accurate depressurizing, and achieved continuous gas production for 30 days, with a total gas output of 861400 cubic meters and a daily average gas production of 28700 cubic meters, which is 5.57 times the first trial production, thus greatly increasing the daily gas production and total gas production. The results show that there existed no abnormal methane content in sea floor, sea water and atmosphere during the whole process. The success of this test shows that it is possible to efficiently and safely develop the gas hydrate in shaly silt reservoirs.

Abstract:The study of the Neoproterozoic granites in the Altun orogenic belt is significant for revealing the area of the Rodinia supercontinent convergent stage tectonic evolution. In this paper, a detailed study of petrology, chronology and geochemistry was carried out for a new division of Qingbaikou gneissic granite in Yaganbuyang area. The U-Pb dating of zircons from the gneissic granite using LA-ICP-MS yielded (883.0±3.3)Ma and (883.1±3.3)Ma, indicating that the gneissic granite was generated in Qingbaikou period. The geochemical analysis shows that major elements are characterized by high SiO₂, Al₂O₃ and K₂O values and low Na₂O, MgO, CaO and TiO₂ values, thus belonging to the calc-alkaline-high-K calc-alkaline series, and peraluminous.REE distribution patterns show negative anomaly of Eu, obvious fractionation of LREE and weak fractionation of HREE, with a clear V trough, which shows the features of crustal derived granite. The gneissic granite is rich in large ion lithophile elements of Rb, Th, LREE, slightly depleted in Ba and mightily depleted in high field strength elements of Nb, Sr, P, Hf, Ti. These characteristics are similar to features of the continental collision type granite. The source rock of the gneissic granite was formed by the partial melting metasandstone from the crust in the subduction-collisional environment about Rodinia supercontinent. Comprehensive study shows that these syn-collisional granites were generated between 871 Ma and 940 Ma, which constrained the timing of the Rodinia supercontinent in Early Neoproterozoic along the Altun orogenic belt. These rock bodies have the characteristics of zonal distribution in space and confirm the existence of syn-collisional granites belt about Rodinia supercontinent on the Altun orogenic belt.

Abstract:The Heijianshan iron deposit represents a typical submarine volcanic rock-hosted deposit of the Aqishan-Yamansu ore belt in Eastern Tianshan Mountains. Abundant irregular iron-rich agglomerates are developed in the brecciated andesite lava (wall rock), and they can be subdivided into five types, i.e., albite-magnetite type, albite-K-feldspar magnetite type, K-feldsparmagnetite type, epidote-magnetite type and quartz-magnetite type, likely representing evolving products of the magmatichydrothermal ore-forming process, which can constrain the ore-forming process and metallogenic environment of the Heijianshan iron deposit. Magnetite compositions of the five types of agglomerates were analyzed using electron microprobe analysis. For the purpose of obtaining precise Fe content, the content of undetermined O was added by difference method and the ZAF matrix correction was conducted. The Ti values of the five types of agglomerates display a positive relationship with the Fe values. Magnetite of the albite-magnetite type has highest Ti content, the albite-K-feldspar magnetite and the K-feldspar-magnetite types show medium Ti content, whereas the epidote-magnetite and quartz-magnetite types are characterized by the lowest Ti content. Also, the Fe content of the epidote-magnetite and the quartz-magnetite types is similar to that of the ores. These features indicate that the albite-magnetite type seems to have been the earliest crystallization product from a residual iron-rich melt, the albite-K-feldspar-magnetite and K-feldspar-magnetite types display features of magmatic-hydrothermal transition, whereas the epidote-magnetite and quartz-magnetite types represent products of hydrothermal alteration. The Fe content of magnetite of each type of agglomerate is higher than its content of the corresponding alteration zone, suggesting a simultaneous relationship between the crystallization of iron-rich agglomerates and hydrothermal activities.

Abstract:The Cryogenian (Nanhua) Period "Datangpo type" manganese deposits in northeastern Guizhou Province constitute the most important manganese resource base of China, and the lithofacies-paleogeographical environment is the most important orecontrol factor. Based on analyzing the lithology and age histogram of detrital zircon U-Pb ages of Qingshuijiang Formation, Liangjiehe Formation, Tiesi'ao Formation and Datangpo Formation, the authors present the stratigraphic division of Nanhuan System. Totally, there are four level II basins, twelve level III basins and eleven Mn-bearing basins according to distinct sedimentary filling patterns in northeastern Guizhou Province. It is suggested that there are nine types of palaeogeographic units in early Datangpo Age based on identifying fourteen types of lithofaces in 1st member of Datangpo Formation. Furthermore, the authors compiled the lithofacies paleogeographic map of Early Datangpo Age of Cryogenian (Nanhua) Period in northeastern Guizhou Province. In conclusion, under the background of continental margin rifting, the authors hold that the sedimentary environment of early Datangpo Age in the study area belonged to the barrier coastal system of continental margin, and the typical "Datangpo type" manganese deposit was closely related to the deep-water limited basin with rapid subsiding behind the barrier.

Abstract:Titanium is known as "the third metal" for its special characteristics and wide range of uses. China is rich in titanium resources, which account for 24.46% of the world's total reserves. As most of China's titanium resources are low-grade primary ores, China has to import high-grade and high-quality ores to meet its demand. Hence, further geological metallogenic studies of titanium resource potential are urgently needed so as to provide a reference for future geological prospecting work. In this paper, Ti deposits are classified into 4 types, i.e., magmatic type, metamorphic type, weathering type and (Quaternary) sedimentary type. The magmatic type Ti deposits were formed by magmatic differentiation and are widely distributed. The most important ore deposits are mainly concentrated in Panxi ultrabasic rock belt and northern margin of the North China platform basic-ultrabasic rock belt. Metamorphic type Ti deposits are closely related to regional metamorphism. The important ore deposits are eclogite type (garnet-amphibolite type) rutile deposits, which are controlled by HP/UHP metamorphic zones. Weathering Ti deposits are controlled by Ti-rich original rock and hot rainy weather and are mostly distributed in Yunnan and Guangxi. Littoral sedimentary placer deposits are distributed along the east coast, especially in the east coast of Hainan Island. During the prediction of this type of Ti resources, the authors delineated 111 prospective areas and predicted the resource potential according to comprehensive summary of titanium resource ore-forming regularities, These prospective areas include 22 class A ones, 27 class B ones and 62 class C ones. Finally, the authors sorted out 12 prospecting areas with better metallogenic geological conditions for the future prospecting work.

Abstract:Oil and gas exploration of Mesozoic strata in Chaoshan depression of Dongsha sea area is believed to have good prospect. Because of its low exploration and study level caused by the limitation of seismic data, oil and gas distribution there is unknown. In order to strengthen the research on the distribution and enrichment of oil and gas in the west of Chaoshan depression, the authors first applied microbial hydrocarbon detection technology to study its oil-bearing property of geological targets. Based on the theory of light hydrocarbon microseepage, the authors used the method of geological microbiology and geochemistry directly detect the anomaly of microbes and adsorbed hydrocarbons on the surface of the study area, and predicted the enrichment area of oil and gas in the underlying strata of the study area as well as its oil or gas properties. The results of microbial hydrocarbon detection show that microbiological anomaly is massively developed in the slope area of the western depression, suggesting that the intensity of light hydrocarbon micro seepage is relatively large in the study area, and there may be oil and gas enrichment zone. Acidolysis hydrocarbon analysis shows possible existence of oil and gas properties for dry gas and condensate oil and gas. The results of microbial hydrocarbon detection indicate that the Mesozoic strata in the Dongsha sea area has a good potential for oil and gas resources.

Abstract:Viruses and bacteria are generally called microorganisms. The disaster of viruses and bacteria is the biggest one encountered by living creatures. It not only has left a serious disaster in the history of human society but also has been an important promoter of the mass extinction in the history of the evolution of the Earth's life. Although it is difficult for viruses and bacteria to form solid fossils, a special molecular fossil has become a magic needle for the detection of biological extinction in geological times. With earth microbiology as the guide and cyanobacteria and green sulfur bacteria molecular fossils as the study case, the authors comprehensively explained relevant research results and interpreted the relevant knowledge of microbiology, viruses and bacteria, and microbial rocks, thus helping people understand the two most important events of mass extinction in the history of the earth's biological evolution. This paper also clarifies the association relationship between human and fungus based on the enlightenment from the agricultural revolution in the process of human evolution.

Abstract:A series of ophiolitic massifs are distributed along the Yarlung Zangbo Suture Zone (YZSZ), southern Tibet. However, the formation settings of these ophiolites are still controversial. Trace elements and Pb isotope geochemical features indicate that the magmas that formed the mafic rocks in the Luqu and Dazhuqu massifs of the Xigaze ophiolite in YZSZ were derived from the depleted mantle source. The La/Sm and Sm/Yb ratios of the mafic rocks show that their parental magmas were produced by ~10% partial melting of spinal lherzolite. Combined with the petrographic observations and major elements of the mafic rocks, the authors hold that they were formed from an anhydrous basaltic magma. Furthermore, the normalized patterns of trace elements and REE of the mafic rocks are very similar to those of N-MORB, except for weakly negative Nb-Ta anomalies. These features indicate that the Luqu and Dazhuqu massifs were formed in the MOR environment. Moreover, the Pb isotope of the mafic rocks indicates that their mantle sources have similar geochemical characteristics to Indian MORB mantle domain. N-MORB normalized trace element patterns of the mafic rocks show that weakly negative Nb-Ta anomalies might have resulted from the process that their mantle source metasomatized old subducted materials.

Abstract:Several small-scale basalt trachyandesite rock masses were found in NNE direction in Emeishan basalts of Huize area, northeastern Yunnan Province. Based on detailed field geological survey, microscopic petrographic analysis, zircon U-Pb dating and rock geochemical test, the authors studied the formation age and geochemical characteristics of these basalt trachyandesites and their tectonic evolution process. LA-ICP-MS zircon U-Pb dating yielded a weighted mean ²⁰⁶Pb/²³⁸U age of(251.6±4.2)Ma (MSWD=0.20) for the basalt trachyandesite, and the alteration ages are(143.5±1.9) Ma and(150.5±2.4) Ma, respectively. The content of SiO₂ in basalt trachyandesite is between 52.09%-54.10%, implying that it belongs to the intermediate basic volcanic rock. The Mg# values of basalt trachyandesite are from 19.88 to 40.86, and the TAS diagram generally shows that it belongs to alkali basalt trachyandesite series. The characteristics of REE and trace elements show that the basalt trachyandesite of Huize was derived from enriched mantle source. In the process of magmatic evolution, a part of clinopyroxene, plagioclase and magnetite experienced fractional crystallization. It is considered that the basalt trachyandesite of Huize is a part of Emeishan basalts, and that it might have been the product of the extinction of Emeishan mantle plume.

Abstract:The LA-ICP-MS zircon U-Pb age, rock geochemistry and zircon Hf isotopic composition of the Shihushan granite located in Dezi Village of Anning area were investigated in this study. The zircon U-Pb dating yielded a magmatic crystallization age of (616±20) Ma and inherited ages of (839±17) Ma, (766±15) Ma and (705.5±9.4) Ma, indicating pluton emplacement in Neoproterozoic Ediacaran Stage. The authors hold that the magmatic crystallization age of (616±20) Ma indicates the pluton emplacement in Neoproterozoic Ediacaran Stage, and the assemblage of inherited ages of (839±17) Ma, (766±15) Ma and (705.5±9.4) Ma represents the splitting of the Rodinia supercontinent. The age of (839±17) Ma may represent the initiation of the breakup of the Rodinia supercontinent, while the age of (616±20) Ma may represent the final stage of the breakup event. The major and trace elements of alkali feldspar granite show the characteristics of A-type granite with high SiO₂-K₂O-Al₂O₃ content, indicating an extensional environment. Zircons from samples have low εHf(t) value (<0). All samples are plotted on the upper crustal evolution area on t-t (Ma) and t-(176Hf/177Hf) diagrams. The two-stage Hf model ages range from 1.77 Ga to 2.31 Ga. According to the Nb/Y-Rb/Y diagram, the petrogenic material mainly originated from the 60% melting of the shale of the Paleoproterozoic lower crust.

Abstract:Since the Triassic, tectono-magmatic activity in West Qinling Mountains has been very intense and the intermediate-acid intrusive rocks are distributed in a NW-trending arc. A lot of effective work has been done by previous researchers, but research on volcanic rocks with less exposure remain insufficient. Petrological, geochemical and chronologic analysis was used for andesite in Maixiu County and Tongren County of Qinghai Province and Ganjia and Dewulu areas in Xiahe County of Gansu Province. The results show that andesite belongs to calc-alkaline series and shows the characteristics of potassium-rich volcanic rocks. Maixiu andesite contains both high-magnesium andesite and magnesian andesite, while Ganga and Deuru andesite belongs to magnesian andesite, being two typical types of volcanic rocks formed by oceanic crust subduction. The formation of andesite in West Qinling area occurred early in the East and late in the west. From west to east, andesite in West Qinling Mountain presents the following characteristics:1) The values of SiO₂ and alkali decrease; 2) The formation of andesite took place earlier; 3) The values of K₂O, Na₂O, ∑REE increase; 4) The values of MF, FL, DI, La/Sm is larger; 5) The values of SI, Mg^# decrease, with significant linear features. The magmatic arc assemblage of Xiahe-cooperative magnesian andesite (mafic diorite) is composed of Tongren-Hezuo magnesian magmatic arc assemblage and Longwu gorge ophiolite belt in the north. Polarity indicates that the oceanic crust plate represented by Longwu gorge ophiolite subducted southward in the Triassic in the northwestern part of West Qinling Mountain.

Abstract:Basic intrusive rock masses are extensively developed in Bogda orogenic belt, and their origin is of great significance to the correct understanding of the geodynamic background of this area. In this paper, the authors studied systematically petrology, geochemistry and zircon U-Pb geochronology of gabbro in the west of Bogda orogenic belt, in order to discuss their petrogenesis and tectonic significance and then to provide a basis for solving geological tectonic evolution of Bogda orogenic belt. Petrogeochemical analysis shows that their SiO₂ values range from 48.08% to 51.03%, and ALK values range from 3.09% to 4.39% (less than 5%), and that they are rich in CaO (6.87%-11.41%), and depleted in Al₂O₃ (12.59%-18.49%). The MgO values range from 3.78% to 7.66%, Mg^#=31.75-65.73 (47.03 on average), and A/CNK=0.60-0.80, indicating that the rocks belong to metaluminous intermediate K calc-alkaline rock series. The analysis also shows that they have low REE (36.30×10^-6-147.72×10^-6), with no obvious fractionation between light and heavy rare earth elements and between heavy rare earth elements. They are obviously depleted in Th, Ta, Nb elements, with no obvious loss of Ti and slight enrichment of U element, showing the characteristics of continental rift magmatism. According to the relevant diagram and the ratio of trace elements and rare earth elements, the gabbro magma probably originated from depleted lithospheric mantle, with the contamination of the crust; their differentiation evolution degree was low; they experienced higher degree of partial melting of the original phase spinel peridotite, and were formed in the intraplate rift environment. Moreover, gabbro LA-ICP-MS zircon U-Pb dating results show that the formation age is (305.0±1.6) Ma, suggesting the late period of the Bogda rift volcanic activity in late Carboniferous. All these data indicate that the west of Bogda rift underwent a conversion from the overall extension stage to the confined extension stage. The analysis of regional geological data shows that there existed a large rift evolution related to magmatism during Late Paleozoic (Early Carboniferous-Early Permian), and the orogenic belt was developed on the basis of rifting, with its formation related to the northward subduction of the Junggar-Turpan-Hami block driven by the Kangurtag Ocean.

Abstract:Junggar Basin is an important area for the exploration and development of volcanic lava in western China. 16 volcanic lava wells were selected for core observation, ordinary thin-section and cast thin-section identification and quantitative statistic analysis under microscope, scanning electron microscopy and X-ray diffraction experiments to study petrological characteristics, pore types, combination characteristics, similarities and differences of basalt, andesite and dacite which are characterized by relative lack of research data on the characteristics of the volcanic lava reservoirs and petrogenetic evolution processes in the Xiquan area, eastern Junggar Basin. Besides, diagenetic evolutionary sequence of volcanic lavas was built and the influence of diagenesis on the pore evolution of volcanic lava was explored. The results show that andesite has a large reservoir space, and its pore types and pore combinations are complex and diverse, which include stoma+phenocryst solution pore+matrix solution pore+dissolution fracture combination, and stoma+phenocryst solution pore+matrix solution pore+dissolution fracture+structural fracture combination. Pore types and combinations of dacite are stoma+phenocryst solution pore+matrix solution pore and stoma+phenocryst solution pore+matrix solution pore+dissolution fracture. Pore types and combinations of basalt are simple, which include structural fracture+dissolution fracture combination, structural fracture+matrix solution pore combination, and stoma+dissolution fracture combination. Volatilization controls the development of original gas hole in volcanic lava. Dissolution, weathering, leaching, and tectonic fracture have greatly improved the reservoir performance of volcanic lava. Post-magmatic hydrothermal and filling have destroyed the reservoir space of volcanic lava. Overall, it is considered that andesite in the weathering and erosion-leaching belt at the top of the Carboniferous in Xiquan area (0-20 m from the top of the Carboniferous) is the most advantageous segment of hydrocarbon accumulation.

Abstract:Located at the westernmost end of the North Qilian orogenic belt, the Chelugou pluton consists predominantly of quartz diorite porphyry and diorite porphyry. Zircon LA-ICP-MS U-Pb dating of the Chelugou quartz diorite porphyry yielded an age of (462.1±3.8) Ma. Rocks from the Chelugou pluton show intermediate-felsic, metaluminous and low calc-alkaline features, with relatively low SiO₂ (61.44%-67.63%), Al₂O₃ (15.09%-16.7%) and A/CNK values (0.90-1.00), and high Na₂O/K₂O ratios (7.47-9.96). They have relatively low rare earth element content (33.40×10^-6-39.27×10^-6) and are characterized by positive Eu anomaly and high LREE/HREE ratios (3.95-6.51), similar to features of typical adakites. All of the rocks are also enriched in Ba, Sr and depleted in HFSEs (e.g., Nb, Ti and Yb). By comprehensively synthesizing geochemical compositions and geological setting for magma rocks within the study area,the authors hold that the Chelugou granitoids were derived from partial melting of subducted oceanic plate related to the northward subduction of the Qilian Ocean underneath the North China Block in Ordovician.

Abstract:There exists a large area of Late Paleozoic magmatic rocks on the western side of Langshan Mountain in Inner Mongolia, whose ages are concentrated on Early Carboniferous to Late Permian. The magmatic rock assemblages of different ages are of great significance for understanding the Late Paleozoic tectonic background of Langshan area. Based on petrology, petrography, geochemistry and Hf isotopes, this study mainly focused on the granodiorites in Chagannaihuduge zone of Langshan area. LA-ICPMS U-Pb dating on two granodiorite samples yielded ages of(299±1)Ma and(293±2)Ma respectively. The mafic minerals in granodiorties are dominated by hornblende and biotite. The geochemical data reveal that the granodiorites are of calc-alkaline nature characterized by enrichment of Na₂O (3.45%-4.96%), high Na₂O/K₂O value (1.33-2.52) and show good negative correlation between P₂O₅ and SiO₂, which is similar to the characteristics of I-type granites. The Hf isotopic signature for granodiorites and their behavior of elemental geochemical characteristics together indicate that their co-magmatic origin mainly derived from Palaeoproterozoic-Mesoproterozoic continental crust and subordinately from mantle-derived magma. The granodiorites show similar patterns on the chondrite-normalized REE patterns, and display relatively high concentration of light rare earth elements (LREEs) but low content of heavy rare earth elements (HREEs) with minor negative Eu anomalies. The overall chemical similarities of these granodiorites on the primitive mantle-normalized variation diagrams display affinity to arc signature. By combining the large scale regional exposures of diorite+quartz diorite+granodiorite rock assemblage and basalt+basaltic andesite+andesite+anganite in Dashizhai Formation, the authors hold that Langshan area was under the tectonic setting of continental margin arc during Early Permian, similar to that of central-eastern part of NNC.

Abstract:Hongshan syenite complex has fairly abundant clinopyroxene with core-rim (core-mantle-rim) structure. By studying the changes in the composition of clinopyroxene, information on the genesis and evolution of rocks can be obtained. Based on detailed field geological survey, the authors used zircon U-Pb chronology and mineralogical studies to obtain the biotite pyroxene syenite zircon U-Pb dating data of Hongshan syentite complex, with the age being(126.9±1.2)Ma, suggesting a product of the thinning peak period of the North China Craton lithosphere. The Mg^# values of clinopyroxene from pyroxene syenite and biotite pyroxene syenite in the Hongshan syenite complex are 39.4-72.5 and 55.4-81.7, with characteristics of high FeO, Na₂O and CaO content and low Al₂O₃, MgO and TiO₂ content. The clinopyroxene generally had the evolutionary trend of diopside and aegirine, and reached an equilibrium state with the melt. The clinopyroxene had a Fe²⁺ to Mg²⁺ substitution relationship during the initial evolution. With the evolution, the magma became richer in sodium and iron, which suggests that the magma system had the characteristics of high temperature, medium oxygen fugacity and richness in alkali. Combined with the clinopyroxene core-rim (core-mantle-rim), the authors hold that there existed a clear contact relationship and discontinuous chemical composition. It is shown that, after the formation of the Hongshan syenite complex, it also underwent the transformation of sodium-rich and iron-rich fluids, causing the clinopyroxene to form a sodium-rich and iron-rich rim. The fluid may have modified the complex from west to east or from the inside of the Hongshan syenite complex to the outside.

Abstract:Tuquan Basin near the west boundary of the Songliao Basin is a Mesozoic sedimentary basin formed above the Paleozoic strata, which has aroused much attention from geologists due to the discovery of light crude oil from the Jurassic strata in recent years. In the past, systematic research on the oil and gas resources from the Paleozoic was very insufficient. In this paper, the methods such as stratigraphic (lithostratic) and sporopollen analysis and source rock test were conducted so as to analyze synthetically the core samples collected from TD-2 well in the Mangniuhai depression of Tuquan Basin. A stratigraphic unit composed of grayish black mudstone and siltstone beneath the Middle Jurassic conglomerate was discovered in TD-2 well, and some spores and pollen were extracted from the unit, which consist of 26 species and 19 genera, including Leiotriletes adnatus,Punctatisporites debilis,Alisporites auritus,A. communis, A. stenoholcus, Klausipollenites schaubergeri, Pityosporites evolutus, Sulcatisporites dalongkouensis, Hamiapollenites indistinctus, Piceaepollenites opimus etc. indicating Late Permian. Combined with the research results such as the stratigraphy (lithostratic) and source rock test, it is reasonably assigned to Late Permian Linxi Formation, and some high-quality source rocks are discovered in this unit. This discovery is significant for confirming the existence of Permian strata in the Tuquan Basin and also for exploring the late Paleozoic oil and gas resources in the Songliao Basin and adjacent regions.

Abstract:Member 6 of Majiagou Formation in south Ordos basin has been eroded in most part of the south Ordos basin, and is hence only distributed in the periphery of the basin. Therefore, less studies have been done on the origin of dolomite in member 6 of Majiagou Formation of the basin. Based on petrologic analysis, cathodoluminescence images, trace elements and carbon and oxygen isotope characteristics, the authors studied the characteristics and formation mechanism of dolomite in member 6 of Majiagou Formation in south Ordos basin. The results reveal that the dolomite of member 6 in south Ordos basin is mainly composed of finemedium crystal dolomite with cloudy cores and clear rims as well as dark red luminescence. The dolomite has relatively low Fe and Mn content (average of 447×10^-6 and 62×10^-6), relatively high K and Na content (average of 517×10^-6 and 252×10^-6) and moderate content of Sr (average of 155×10^-6). Average value of δ¹³C and δ¹⁸O is -0.617‰ and -7.6‰ respectively, moderate indicating its marine origin. The trace element content of cloudy cores is close to that of clear rims, which indicates that they were formed in similar diagenesis environments. The cloudy cores were formed in a shallow buried environment by seepage reflux dolomitization model, while the clear rims were recrystallized and adjusted in a deep buried environment.

Abstract:The continental Permian-Triassic boundary is one of the most important problems in the study of the global PermianTriassic boundary. Based on collecting and analyzing tuff samples, the authors conducted LA-ICP-MS U-Pb dating of zircon and obtained an age of (255.5±1.1)Ma in the stratotype section of the middle part of Xingfuzhilu Formation. A total of 20 species of 17 genera sporopollen fossils were discovered on the top of the tuff in the stratotype section. The age of Xingfuzhilu Formation is late Late Permian-early Early Triassic according to the sporopollen fossils. It is considered that the middle part of Xingfuzhilu Formation should be late Late Permian whereas the upper part belongs to early Early Triassic. The boundary of Permian and Triassic strata in Da Hinggan Mountains is actually located inside Xingfuzhilu Formation. Moreover, the Late Permian-Early Triassic strata are of continuous deposition in Da Hinggan Mountains. With red-red features as a dividing point, Xingfuzhilu Formation totally reflects the thermal, arid and strong oxidation climate. It can be dated back to late Late Permian-early Early Triassic. The red beds came into existence from the late Late Permian in Da Hinggan Mountains. In addition, the climate changed from warm and rainless to arid and thermal, which is in accord with features of neighbouring North China and Junggar basin in Xinjiang. These data prove that the thermal, arid and strong oxidation climate did exert an profound influence on Da Hinggan Mountains.

Abstract:Situated in the southwestern segment of Qinzhou-Hangzhou joint belt, Bancheng area of southern Guangxi is a pivotal area in understanding the geological tectonic evolution history of South China since the Paleozoic. Late Devonian to late Permian siliceous rock sequences are outcropped in this area. In recent years, the authors conducted systematic field geological survey and found that there exist a series of siltstone intercalations in late Paleozoic siliceous rock sequences of the Shiti reservoir in Bancheng Town, Qinzhou City. In this paper, LA-MC-ICP-MS U-Pb isotopic dating was performed for detrital zircons from two siltstone intercalation samples of the lower and upper late Paleozoic siliceous rock sequences. Detrital zircon U-Pb age spectra shows that there are four main age groups of 407-573 Ma (early Paleozoic), 644-954 Ma (Neoproterozoic), 1124-1636 Ma (Mesoproterozoic) and 2368-2548 Ma (Early Paleoproterozoic-late Neoarchean), which recorded four major tectonic thermal events in this area. These four periods of tectonic thermal events are consistent with the ages of widely developed magmatic rocks in Yunkai area of the Cathaysia Block, indicating that Yunkai area might have been major depositional provenance for the siltstone intercalations of late Paleozoic siliceous rock sequences. The depositional provenances of the lower and upper late Paleozoic siliceous rock sequences are significantly different, and there is a general tendency toward increasing complex and relatively older age of detrital zircon from the lower to the upper of late Paleozoic siliceous rock sequences, indicating that the Yunkai Block has experienced rapidly erosion and uplift process after Caledonian orogeny in the southwestern segment of Qinzhou-Hangzhou joint belt. Detrital zircon U-Pb age spectra of the sandstone intercalations of late Paleozoic siliceous rock sequences imply that the Qinzhou-Fangchang Basin was in an extension tectonic setting in Late Paleozoic period.

Abstract:Three stages of sedimentary environment evolution since MIS 5 were recognized based on the data of grain size analysis, AMS¹⁴C dating, OSL dating, sedimentary characteristics, benthic foraminifera and ostracoda identification in the upper part of core YRD-1101 drilled in the modern Yellow River Delta, and comparison with surrounding boreholes. Three stages of sedimentary evolution are identified. (1)Interactive deposition of rivers and marine facies were formed during the Late Pleistocene-Early Holocene. Among them, the transgressive sediments in the MIS5c phase were formed in a medium hydrodynamic conditions, the transgressive sediments in the MIS3 phase were formed in a weak hydrodynamic environment, and the river sediments in the MIS2 phase were formed in a strong hydrodynamic environment. (2) The nearshore and shallow sea deposits during the Holocene formed in a strong and stable environment. (3) Modern Yellow River Delta sediments deposited since 1855 A.D. were formed in weak to medium sedimentary dynamic environments. Sea-level changes and neotectonic subsidence have been the major factors controlling the sedimentary evolution on the western margin of the modern Bohai Sea since MIS 5. In addition, the sediments were transported to the study area from Yellow River, which had a significant influence on transgression intensity.

Abstract:Nankou-Sunhe fault is one of most importance active faults in Beijing plain and one part of Bohai Bay-Zhangjiakou fault belts. This paper builds magnetic polarity chronology of borehole sedimentary strata based on magnetic stratigraphy and sedimentology with drilling and paleomagnetism and ¹⁴C samples testing, analyses and discusses the active features of NankouSunhe fault in the north segment since Quaternary period. The research indicates that:the fault activity changed from high to low intensity in the early stage of early Pleistocene(2.58-0.99 Ma)and turned into high intensity in the late stage of early Pleistocene (0.99-0.78 Ma), from strong to low intensity again in the Middle Pleistocene (0.78-0.126Ma), and then from low to high again intensity (0.126 Ma-present). This active feature is consistent with west mountain of Beijing uplift which shows the characteristics of high-low-high intensity.

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