Abstract:The Sinian-Paleogene period in South China developed several sets of hydrocarbon source rocks. Because of the multistage tectonic movements, the preservation conditions of oil and gas are poor. Over the past 60 years, oil and gas survey in complex structure areas outside the basins has not made a major breakthrough except for Sichuan, Jianghan and Subei basins. Based on field geological survey, geophysical exploration and researches on hydrocarbon accumulation conditions, the authors hold that, because the Wufeng-Longmaxi Formation has well-developed organic matter-rich shale, moderate thermal evolution, Shiniulan Formation provides good reservoir, and syncline wing is blocked by reverse faults, the shale gas, oil and gas accumulation conditions are very favorable. Well Anye-1 made the "four-storey" type oil and gas breakthrough in the Shiniulan Formation, Wufeng-Longmaxi Formation, Baota Formation and Qixia Formation. In the Shiniulan Formation, more than 10×10⁴ m³ industrial gas is produced everyday. New areas, new layers and new types are therefore opened up for oil and gas exploration in South China. The breakthrough of well Anye-1 confirms the fact that there exist the reservoir-forming conditions for the coexistence of conventional and unconventional oil and gas in the complex structure areas outside the basins in northern Guizhou and southeastern Chongqing. These achievements are of great significance for the development of residual syncline oil and gas exploration in the adjacent areas.

Abstract:Lots of geological and petroleum studies have been conducted in the Yingen-Ejin (YE) Basin in such aspects as the evolution of the Carboniferous-Permian basin, the sedimentary filling, the regional distribution and geochemical characteristics of source rocks, the thermal evolution history of hydrocarbon source rocks, and the tectonic and sedimentary evolution and hydrocarbon preservation after the Carboniferous-Permian deposition. Based on the achievements obtained from these studies, the authors hold that the Yingen-Ejin Basin is composed of superimposed basins composed of a Carboniferous-Permian continental rift basin and Mesozoic inland basins. Petroleum prosperity is proved by the existence of several Carboniferous-Permian source strata characterized by great thickness, moderate-high abundance of organic matter, the existence of main kerogen type Ⅱ, and moderatehigh evolution stage. The preferred oil and gas prospecting areas were sold by the Ministry of Land and Resources, and the enterprises have increased the investment of the exploration. The first drilling hole (Guaican 1st Well) of the Guaizihu depression in the Wutaohe exploration area obtained the initial daily production of 51.67 m³ oil and 7290 m³ natural gas (open flow potential) with a small amount of condensate gas, and the first drilling hole (Yanhacan 1st Well) of the Hari depression in the Wentugaole exploration area received the industrial gas flow of 91500 m³ daily production (open flow potential) with a small amount of condensated oil. These achievements realize the great breakthrough of oil and gas exploration which started in 1955. Based on the age constraints on the oil and gas strata in the two wells and the comparison of oil and gas sources, the authors consider that the ages of oil and gas strata should be the Permian. Additionally, the Carboniferous-Permian strata should be the main objects of oil and gas exploration in that they have great prospects of resources.

Abstract:The geosyncline-platform theory prevalent from the middle decades of the 19^th century to the middle of the 20^th century was established on the basis of the research on the geology of Europe and eastern North America in the Atlantic hemisphere by western geoscientists. The theory of plate tectonics that originated in the 1960s was grounded on geological and geophysical surveys of modern oceans. However, the earliest explanation for continental tectonics used by plate tectonics was based on the analysis of the Paleozoic orogenic belts of Europe and North America on both sides of the Atlantic. It is obvious that the tectonics theories and models based on the research results of Europe and North America are not comprehensive in that valuable geological data and information of Asia in the Pacific hemisphere, especially those of China and its adjacent areas, are not included. Through the compilation of the International Geological Map of Asia at a 1:5,000,000 scale (IGMA5000) and comparative studies of global tectonics, the authors have found that China and its adjacent areas situated in the center of Asia are the most complex region in geological structure and evolutionary processes during the Phanerozoic in Asia, even in the world. The Ural-Mongolia-Hinggan Paleozoic orogenic belt in the Paleo-Asian tectonic domain is the largest in scale, the longest in evolution history, and the most complicated in geological structure on the earth. Southwestern China, especially the Tibetan Plateau, has the biggest exposure width, and possesses the most complete geological records within the Tethyan orogenic belt on the globe. The Pacific domain of eastern China is characterized both by the East Asian margin Mesozoic orogenic belt and the West Pacific Cenozoic trench-arc-basin system, and by the wide marginal Pacific pericontinental reactivated zone. All of these characteristics make China and its adjacent areas the most necessary locality in carrying out the Phanerozoic tectonic research. We, Chinese geoscientists, must use to the best regional advantage of China in global tectonic research, with the multisphere tectonic view of earth system serving as a guide in studying the tectonics of China and make our contribution to the development of international geoscience and the improvement of modern tectonic theory.

Abstract:The Early Paleozoic tectonic stage of the North China Craton (NCC) began around 520 Ma, when Gondwana assembled in its peak tectonism. The Middle Cambrian deposition occurred on older strata or basement rocks along margins of the NCC. Then the marine environment expansion and its extensive invasion led to the late Middle Cambrian marine deposition, with the Mantou Formation and afterward strata distributed throughout the NCC. New research results of the Bainaimiao arc belt to the north of northern NCC indicate that the arc was active from 520 Ma and lasted until 420 Ma, which could extend to east Siping in Northeast China. Along the southern edge of the NCC the northward subduction of the Shangdan Ocean took place during ca. 514-420 Ma. Marine regression occurred later than the Majiagou phase in Middle Ordovician in most parts of the NCC. Recently some Devonian plutons and volcanic rocks were recognized in northern NCC. The Late Carboniferous sedimentary sequence with the ‘G’ layer of bauxites at its bottom overlies the Middle Ordovician limestone in unconformity. The bauxites were derived mainly from ashes produced by volcanism mainly in the Inner Mongolia Paleo-uplift during Paleozoic period, particularly in latest Early Carboniferous to Early Permian when the northern margin of the NCC evolved as an Andean-style active continental margin. The sequence is mainly clastic formations composed of coal-bearing sandstones and siltstones interlayered with marine limestone and volcanic ash, which demonstrates that they formed in a terrestrial-marine transitional or terrestrial environment with volcanic arc settings. After late Early Permian a terrestrial environment was dominant in the NCC. In southern NCC and the Qinling Orogenic Belt spreading of the Mianlue Ocean between the South China Craton and the South Qinling Block was sustained in Late Paleozoic, and the northward subduction-accretion of the Mianlue Ocean was active in Late Paleozoic. In Triassic the collision between the South China Craton and the South Qinling Block along the Mianlue suture resulted in intense shortening and uplift of Qinling Orogenic Belt and HP/UHP metamorphism documented in Hong'an-Dabie-Sulu terranes. Meanwhile in northern NCC significant changes in tectonic deformation and magmatism occurred in Late Triassic. In the Panshan region, Xiabancheng region and Niuyingzhi region of northern NCC, intense regional folding and thrusting took place around 210 Ma or slightly later, suggesting that the NCC entered into its initial decratonization stage.

Abstract:The source rock of Upper Permian Rejuechaka Formation in Laxiongcuo area of Qiangtang Basin is characterized by dark gray-ash black and thin-very thin layers. An analysis of organic matter shows that total organic carbon content varies between 0.31% and 0.72% in the source rock, mainly reaching a poor-medium standard. The organic matter mainly belongs to II₂ type. Parent material of the organic matter was derived from a reducing environment with considerable salinity, and mainly came from plankton, algae, pilze with the mixture of a small amount of higher plants. The thermal evolution degree reaches high maturity stage. The discovery of the source rock further suggests that Paleozoic source rock has good hydrocarbon generating potential. The result obtained by the authors provides basic geological information for the assessment of oil and gas resources in Qiangtang Basin.

Abstract:The Jurassic Da'anzhai Formation in the Sichuan Basin is a typical layer characterized by the development of tight oil. Exploration results reveal that the Daanzhai reservoir is mainly lacustrine limestone reservoir in lithology. The tight oil exploration results of Jurassic Daanzhai Formation has aroused much interest; especially during the recent exploration of Duan shore shallow lake facies in the GST-MX area of southern Sichuan, Da'anzhai Formation was frequently seen, and the deployment of GQ1H led to the obtaining of high-yield industrial oil flow in Da'anzhai Formation. The newly drilled well GQ1H indicates that dolomitic rocks have favorable reservoir condition and oil potential, and is also the lithology of "sweet spot" distribution. Comprehensive analysis of old-wells'reinvestigation data, cores, cuttings, rock chips and well logging shows that the lithology of dolomitic reservoir includes dolomitic limestone, limy dolomite and micrite-crystal powder dolomite, the reservoir space is mainly composed of intergranular pores, interparticle dissolution pores and microfractures, and the dolomitic reservoir has the good reservoir condition. The imaging logging displays the development of solution pores, and the degree of dolomitization in the southern part of central Sichuan basin is higher than that in the northern part. According to the comprehensive analysis of carbon and oxygen isotopes, X-ray diffraction, characteristics of formation water and the ancient landform, the authors preliminarily hold that, although Da'anzhai Formation in the Sichuan basin was a freshwater lake during the deposition of Da'anzhai Formation, there still existed some dolomitic reservoirs locally under the control of ancient landform, ancient climate, sedimentary environment and change of lake-level. The understanding obtained by the authors has laid a solid foundation for deepening the understanding of the relatively high quality Jurassic reservoir in central Sichuan Province.

Abstract:The Danizhuang copper deposit is a small porphyry deposit discovered from Luzong basin in recent years. The authors investigated wall rock alterations of the Danizhuang copper deposit on the basis of detailed field observations and petrographic and mineralogical studies, and revealed that the alterations include potassic alteration, beresitization and carbonatization. The characteristics of mineralization, the sequence of mineral deposition and the ore-forming stages, i.e., potassium silicate stage, sulfide stage, carbonate stage, were determined. The sulfide stage can be further divided into quartz sulfide sub-stage and epidote-chlorite sub-stage. The authors collected magmatic rocks (orthophyre) related to mineralization and obtained the age of (126.6± 1.8 Ma) by LA-ICP-MS zircon U-Pb dating, which belongs to Early Cretaceous and was related to the intrusive activity of Shuangmiao Formation. Based on a comparison with similar deposits in other volcanic basins of eastern China, the authors discussed ore-control factors for the formation of this type of deposits, which provides reference for finding porphyry copper deposits in this area.

Abstract:In this study, a series of analyses such as LA-ICP-MS zircon U-Pb isotopic dating and major elements, trace elements and Sr-Nd isotope composition investigation were performed for the syenogranite located in the deep layer of the Bianjiadayuan Pb-Zn-Ag polymetallic deposit, Inner Mongolia. Formed during the magmatic concentration period of early Cretaceous in southern Da Hinggan Mountains, the syenogranite in this deposit has age of (140.31±0.34) Ma. There were at least two periods of magmatic activity in the study area:Acid magma invaded in the early period, whereas intermediate magma and basic magma invaded about 10 Ma later. Ore-forming and rock-forming activities occurred over the same period. Geochemistry of major elements in the syenogranite is characterized by high SiO₂ and K₂O and low MgO, CaO and TiO₂ with A/CNK ratio between 0.98 and 1.19, suggesting metaluminous-weakly peraluminous series. The syenogranite is enriched in LILE such as Rb, Th, U and K and depleted in HFSE such as Sr, P and Ti. The ΣREE values are slightly high. The δEu lies between 0.12 and 0.14, exhibiting significant negative Eu anomalies. The initial ratio of (⁸⁷Sr/⁸⁶Sr)_i is between 0.7066 and 0.7077, while the initial ratio of (¹⁴³Nd/¹⁴⁴Nd)_i is between 0.5121 and 0.5122 (t=140 Ma); ε_Nd(t) values vary in the range of-5.0 to-6.6. Therefore, the petrogenetic materials were the products of partial melting of mafic-ultramafic source rock in middle Proterozoic lower crust. The analyses reveal that the syenogranite in the Bianjiadayuan deposit is A-type granite formed in the environment of high temperature and low pressure with the impact of the post-orogenic extension of Mongolia-Okhotsk scissor-type closed orogeny and lithospheric thinning in early Cretaceous. The high temperature and low pressure environment was probably related to the regional lithosphere demolition effect.

Abstract:The Late Mesozoic Dahutang tungsten deposit, as one of the largest tungsten deposits in the world, is a recently discovered deposit in Jiangxi Province. It is situated in border area of Wuning, Xiushui and Jing'an counties, and also located in the eastern part of the Neoproterozoic Jiangnan orogen. This area belongs to Mesozoic W-Cu-Mo polymetallic ore-forming belt in South China Block with widespread Jinningian diorites and Yanshanian granites. In this study, the authors investigated the petrography, mineralogy, zircon and cassiterite U-Pb geochronology and trace element concentrations of the Neoproterozoic and Yanshannian granitic intrusions in the Shimenshi ore district. Zircon U-Pb dating results of the Neoproterozoic biotite granodiorites and Yanshannian biotite granite porphyry, greisenized fine-grained granites and greisenized biotite granite porphyry are (829.9±4.7) Ma, (145.5±3.6) Ma, (152.6±2.0) Ma and (154.2±1.7) Ma, respectively. In particular, the crystallization ages of the Yanshannian granites are consistent with the new cassiterite U-Pb age results obtained by the authors. The tungsten content in cassiterite from the ore-related fine-grained biotite granites is obviously higher then tungsten content of other Yanshannian intrusions. This implies a higher tungsten concentration in the fine-grained biotite granitic magmas. Apparent temperatures for zircon crystallization calculated by Ti-in-zircon thermometer suggest lower temperatures of Yanshannian magmas with weighted average temperature ranging from 734℃ to 788℃. Trace element concentrations of zircon exhibit that fine-grained biotite granites were formed under low oxygen fugacity condition, which was favorable for the formation of tungsten ores.

Abstract:Previous studies have deeply examined the Neoproterozoic I-type and S-type granites on the western margin of the Yangtze Plate, whereas very insufficient attention has been paid to A-type granites, and hence their petrogenetic nature and tectonic implications are still controversial. In this paper, the authors report the results of a detailed study of the newly discovered Lugu Atype granites in the Yangtze Plate, using LA-ICP-MS zircon U-Pb geochronology, petrology, and whole-rock geochemistry, with emphasis placed on the petrogenesis and tectonic setting of the A-type granites. The Lugu granitoid consists of alkali feldspar granite and monzonitic granite that yielded zircon U-Pb ages of (806±5) Ma and (815±5) Ma by LA-ICP-MS, respectively. The Lugu granitoid is deduced as the Neoproterozoic magmatic product. The Lugu granitoid is characterized by high SiO₂ (71.2%-76.1%), high total alkali values (K₂O + Na₂O values from 6.73% to 8.95%), high K₂O/Na₂O ratios(1.89-3.60)and peraluminous features (A/CNK=1.07-1.49). Both[FeO^T/(FeO^T+MgO)] versus SiO₂ and[(Na₂O+K₂O)-CaO] versus SiO₂ plots indicate ferroan and alkali-calcic signatures typical of A-type granitoids. The content of rare earth elements of alkali feldspar granite and monzonitic granite is high (∑REE=221×10^-6-387×10^-6), and both rocks show enrichment of LREE rather than HREE with a right-inclined REE patterns for (La/Yb)_N ratios from 3.42 to 9.69. Both type rocks have obvious negative Eu anomaly (δEu=0.10-0.34). Meanwhile, the Lugu granitoid has relative high content of Zr, Nb, Ce and Y with high ratios of Ga/Al, Y/Nb, Yb/Ta and Ce/Nb, showing that it is a typical A₂-type granite. Combined with the data on geochemistry and regional geology, the authors hold that the Lugu Neoproterozoic A₂-type granite was derived from the partial melting of pelitic rock in early Neoproterozoic subduction orogeny.

Abstract:Mesozoic volcanic rocks are widely exposed in Zhenglan Banner of southeast Inner Mongolia. The volcanic rocks mainly consist of rhyolite, trachyte, porphyroclastic lava, ignimbrite, and obsidian, in which the porphyroclastic lava is the most developed.According to the results of the zircon LA-ICP-MS dating, the U-Pb zircon age of rhyolites is (141.4±0.7) Ma, that of felsitic mortar lava is (141.6±0.6) Ma and that of ignimbrite is (139.4±0.7) Ma. Within the error range, the formation ages of the three kinds of rocks are the same, which indicates that the time of the volcanic activity (from effusion to explosion and extrusion) lasted a short time. So they should be assigned to early Cretaceous Zhangjiakou Formation. Except for very few samples, the porphyroclastic lava that extruded in the late phase and the rhyolite-trachyte belonging to the early phase effusion facies are extremely consistent in the geochemical characteristics. They are rich in silicon and potassium, and poor in Ca, Mg and Al. So they could be classified as trachyte-rhyolite combination, and some samples have the features of pantellerite. They are enriched in Rb, Th, U and other large-ion lithophile elements, and strongly depleted in Ba, Sr, Ti, P. The chondrite-normalized REE patterns show enrichment of light rare earth elements (LREE), strong negative Eu anomalies, and significant fractionation of LREE and HREE for the volcanic rocks (La_N/Yb_N=6.87-42.74, except for LQ-38). Compared with the early phase effusion facies lava, porphyroclastic lava has higher silicon and lower alkali, which shows that the magma chamber experienced obvious crystallization differentiation after effusion of the rhyolite and trachyte in the magma event. Then the magma with higher silicon and lower alkali extruded out of the earth's surface. The volcanic rocks of Zhenglan Banner area have the characteristics of A-type granites and possess the geochemical characteristics of A₁ type and A₁-A₂ transition granite. The Nb/Ta ratio of the extrusive porphyroclastic lava and effusive rhyolites is 10.46-24.02, which is between the values of the crust and the mantle magma; Y/Nb, Ti/Yb, Ti/Zr also reflect the characteristics of crust-mantle mixing; Rb/Sr ratio is between 0.61-64.51(>0.5), reflecting the characteristics of crust source. These data suggest that the volcanic rocks might have been produced in an extension environment of the transportation period of anorogenic and post-orogenic activities, mainly being intraplate anorogenic activity. In addition, the volcanic rocks were probably derived from partial melting of the Precambrian lower crust which was strongly transformed by Mesozoic underplating and metamorphism.

Abstract:The western Kuqa foreland thrust belt hosts the best surface salt structures in China, and hence can be regarded as a natural laboratory for salt structure research. Previous researches have been mainly focused on the underground salt structures, such as the identification of the underground salt structures, the segmentation of the underground salt structures and the formation mechanism of the salt structures, while the researches on the surface salt structures in this region are relatively less. Based on previous researches, the authors used the methods of field mapping, seismic interpretation and remote sensing images interpretation to analyze the deformation characteristics of the Quele salt nappe in the western Kuqa foreland thrust belt. The development of the Quele salt nappe was controlled by the Quele thrust fault, and the salt rock of Kumugeliemu Group rose to the surface with the thrust fault. The Quele salt nappe is characterized by segmentation, and the deformation characteristics change from west to east. In the western and central part of the Quele salt nappe, the overburden of the salt is intact, and the salt rose to the surface only along the thrust frontier of the nappe. The salt structure pattern of the western and central part of the Quele salt nappe belongs to "open-toed advance salt sheet". Nevertheless, in the eastern part of the Quele salt nappe which is also called Charerhan Namakier, the overburden of the salt was eroded and the salt was driven to flow downward by gravity after the migration of the salt to the surface. The Charerhan Namakier belongs to "extrusive advance salt sheet". The topography of the Charerhan Namakier has been strongly affected by the surface runoff and rainfall, which has caused a lot of karst caves and salt hills to form at the surface of the Charerhan Namakier. Heavy rainfall could affect the advance way of the namakier, making the Namakier advance as "surging flow". The deformation characteristics of the competent interlayers can reflect the rheological strength of the salt. The deformation patterns of the competent layers inside the Charerhan Namakier are more complicated, indicating that the salt in the Charerhan Namakier has experienced stronger rheology, resulting from the lack of limit of the overburden and the full effect from the surface runoff and rainfall.

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