Abstract:Since the 1980s, natural evolution and intense human activities have superimposed a significant change in the pattern of resources and environment in the Yellow River Basin, which further affects its development and utilization distribution and leads to a lot of problems such as resource shortage, environmental degradation and ecological destruction. From the perspective of earth system science, it is urgent to study the changes of the resources and environment pattern in the Yellow River Basin, identify major resources and environment problems, and put forward solutions, so as to provide decision-making basis for the sustainable development of the Yellow River Basin. With "life community of mountains, rivers, forests, fields, lakes and grasses" concept and earth system science theory as the instruction, according to the investigation of multisource and multiphase data, this paper analyzes the changes in eleven major resources environmental patterns and regional differentiation in the Yellow River Basin in the last 40 years from 1970 to 2015, including climate, mountainous area and hydrology, identifies the major geological resources and environment problems, and advances some suggestions on the geological work. The results show that the climate of the Yellow River Basin as a whole has an obvious trend of warming and drying, and the phenomenon of warming and humidity appears locally. In recent years, the total area of water and wetland has been decreasing, and the runoff has been decreasing. Some of the main tributaries are seriously polluted, and the aquatic biodiversity has been reduced. In addition, the mountain ecosystem is fragile and gradually restored, the impact of local human activities is intense, the farmland area shows a downward trend, and the farmland production potential in the downstream area is increasing obviously. Moreover, vegetation cover shows a slow increase trend and local degradation, grassland area continues to decrease, grassland ecosystem degradation is obvious, the trend of desertification expansion has been contained, and the overall situation is still grim. In this case, frequent natural disasters, serious water disasters and concentrated geological disasters have led to the formation of such two high incidence areas in southern Gansu as Loess Plateau and Mountains. The continuous rise of urban construction land area leads to the spread of land area from the downstream area to the middle and upper reaches, which shows the cluster distribution characteristics of multiple construction land cores connected by axes. As a result, the center of population distribution further deviates to the east and increases along the central city, trunk stream and traffic lines. The overall GDP shows an upward trend, but manifests a decline from east to west, from the main stream or tributary coast to both sides and from the central city to the surrounding. In order to protect the ecological environment of the Yellow River Basin, promote the high-quality development and solve the diverse geological resources and environmental problems, it is suggested that geological work should be guided by the theory of earth system science to carry out systematic investigation and research on the major geological resources and environmental problems of the Yellow River Basin. Based on the research method of earth system science, we should carry out interdisciplinary cooperation and integrate regional geological survey.

Abstract:China is one of the countries with the most serious earthquake induced landslide disasters in the world. Considering geological structure, landform, stratigraphic lithology, river and ground motion parameters, and aiming at the seismic fortification level exceeding the probability of 10% in 50 years, the hazard assessment of seismic landslide based on information value and Newmark displacement model were carried out respectively. Based on the most unfavorable principle, a comprehensive zonation of the seismic landslide hazard reveals that in China, the high hazard areas of seismic landslides are concentrated in the boundaries of five active plate boundaries or geomorphic transition zones, such as the north-south tectonic belt, the periphery of Qinghai-Tibet Plateau, the periphery of Ordos, the Tianshan Mountain range and the Taiwan Mountain range. The analysis of the impact of seismic landslide hazard on cities in mountainous areas reveals that Yunnan, Sichuan, Gansu and Taiwan, among the 34 provinces, are seriously affected, and 48 of the 370 major cities are severely affected, and 44 of them have active faults crossing. It is summarized that among the 9 national development priority zones, the national and provincial optimized development zones are generally suitable for urban development and construction; the 25 urban agglomeration and economic zone are relatively suitable for urban development and construction, but the central Yunnan, Chengdu-Chongqing, Lanzhou-Xining urban agglomerations and Guanzhong-Tianshui economic zone are seriously affected by seismic landslide hazard. Among the 14 concentrated contiguous severe poverty areas, the western Yunnan border, Wumeng, Qinba and Liupan areas are seriously affected by seismic landslide hazard; the three deep poverty state areas, such as the Liangshan prefecture of Sichuan Province, Nujiang Prefecture of Yunnan Province and Linxia Prefecture, Gansu Province, are also seriously affected. It reminds us that these regions require special attention in geological disaster prevention and national territory spatial planning. The results can provide reference for urban development, land-use plan and detailed seismic landslide risk management in national scale.

Abstract:Ancient buried hill is a main rich area of hydro-geothermal in China, which has the characteristics of wide distribution, great potential and good development and utilization conditions, and it is also the area with relatively serious land subsidence. Therefore, clarifying the influence mechanism of ground subsidence in the buried hill area is the basis for the reasonable planning, development and utilization of regional groundwater resources and geothermal resources. Based on the mechanism of land subsidence, with Xiong'an district as an example, combined with analysis on the Quaternary thickness, clayey soil content, water level change, soil consolidation, groundwater recharge and its withdrawal, the influence on land subsidence by development of geothermal was studied, which indicates that the occurrence of land subsidence in Xiong'an new area is mainly affected by two factors:over-extraction of groundwater in Quaternary and unbalance of sandstone thermal reservoir. Among them, the overexploitation of groundwater is the main factor of land subsidence and the disordered development of sandstone thermal reservoir is the secondary one. Although the development of carbonate reservoir will cause the decrease of reservoir pressure, the reservoir will not produce obvious compression deformation under the influence of the compression performance of carbonate. As a result, the research can provide support for land subsidence prevention and energy planning in Xiong'an new area.

Abstract:Big data is creating a new approach to geological research, pushing traditional qualitative geological research methods to the level of quantitative research. Antimony ore is the traditional preponderant mineral resources in China, but now it depends on import and becomes our critical metal. Based on the geological big data of antimony deposits, our studies summarize the spatial distribution regularity of antimony deposits, specifically reveal the spatial distribution of antimony in grade-Ⅰ, grade-Ⅱ and grade-Ⅲ minerogenetic belts, and quantitatively analysis the metallogenic density and intensity of antimony deposits in the provinces, cities, counties and III level metallogenic belts in China. The research shows that antimony deposits are distributed in all metallogenic domains in China, and the south China metallogenic province is the most important one with more than 59% resources reserves in the whole world. Hunan is the province with the largest amount of antimony ore and the largest mineralization intensity in China. According to the statistics of prefectural cities, Hechi City of Guangxi has the largest number of antimony deposits and Loudi City of Hunan has the largest mineralization intensity. According to county level statistics, Hechi City in Guangxi has the largest number of antimony deposits, while Loudi City in Hunan has the strongest ore-forming intensity, up to 3330 t/km². The statistics of the metallogenic belts shows that the western part (Ⅲ-78) of southern Yangtze uplift is a metallogenic belt with the largest number of antimony deposits and the largest ore-forming density; while, central Hunan-northcentral Guangxi (Ⅲ-86) is a metallogenic belt with the strongest ore-forming intensity in China. With the development of exploration work, the new addition of antimony resources will be transferred to the depth of crisis mines such as Banxi and Longshan in Hunan province and western areas such as Tibet. The focus of geological prospecting and mining development will also move downward and westward.

Abstract:Bauxite is the main source of metal aluminum. In recent years, with the rapid economic and social development and the gradual progress of urbanization, China's aluminum demand is increasing year by year. In order to deepen the understanding of the spatial distribution and geological characteristics of bauxite and grasp the trend of bauxite exploration and development, this paper briefly summarizes the distribution characteristics of bauxite, the main types and the distribution of bauxite in the main resource countries, and emphatically introduces the new progress of bauxite exploration and development in recent years. Based on ore genesis, bauxite is divided into two types, lateritic type and karst type. The former is mainly distributed in western Africa, north South America, India, Southeast Asia, northern and southwestern Australia, while the latter primarily occurs in southern Europe, Caribbean region, western Asia and China. As to the exploration of bauxite, among the main bauxite-rich countries, Guinea, Russia and Australia focus on reserve addition of large mature mines, while Brazil, Ghana and Jamaica on exploration of new prospective areas. As for bauxite development, Australia, Guinea and China are currently the world's leading producers of bauxite, which together accounted for about 70% of the world's total production in 2019. In the first half of 2020, there was a panic drop in prices of major metals due to the COVID-19 epidemic. Despite the recent rebound trend in the prices of major metals, the United States, Brazil, India and other major economies in the world are still in the grip of the epidemic; the United Kingdom, France, Italy and other European Union countries are still facing great pressure to prevent the epidemic, and there is also the possibility of a second wave of the epidemic in the world. In this context, bauxite exploration and development situation is still very variable.

Abstract:The world's phosphate ore reserve nearly totals 69.5 billion tons (2019), but its distribution is uneven, more than 80% of which is concentrated in North Africa. Especially, Morocco and Western Sahara are the world's richest countries in phosphate resources, with reserves of 50 billion tons in 2019, accounting for nearly 72 percent of the world's total. At present, the sedimentary phosphate deposit used in the world is the most important type, and most of these deposits were formed in two periods, Sinian-Cambrian and Mesozoic-Cenozoic. The former is represented by the large amount of Marine phosphate deposits produced in southwest China, while the latter is most typical of the North African phosphorous metallogenic province from Morocco and Western Sahara to Egypt. In 2019, the top 10 phosphorous producing countries were China, Morocco and Western Sahara, the United States, Russia, Jordan, Saudi Arabia, Vietnam, Brazil, Egypt and Peru, with a total phosphate ore output of more than 200 million tons, accounting for 89.29 percent of the world's total. Traditionally, the United States, Russia, Morocco and China are the main exporters of phosphate rock. However, with the development of the phosphorus resources in North Africa and the Middle East, coupled with the continuous reduction of phosphate resources in traditional supply areas, North Africa and the Middle East have gradually become a production and supply center of the world. Five of the world's top 10 phosphate rock exporters in 2018 were in North Africa and the Middle East, and Morocco in North Africa is the largest phosphate rock exporter. In terms of phosphate fertilizers, in recent years, the world's importers mainly include Indonesia, Brazil, the United States, Malaysia, France, Australia, Bangladesh, Romania, Paraguay, and the Netherlands; exporters are China, Egypt, Morocco, Israel, Australia, the Netherlands, Lebanon, Mexico, Peru and Argentina, etc. The United States, which was once a major exporter of phosphate fertilizer, gradually turned into an importer after 2006; India, a big importer of phosphate ore, has basically achieved self-sufficiency in phosphate fertilizer in recent years. With its undominant phosphate ore reserves (3.2 billion tons in 2019, accounting for 4.61% of the world's reserves), China is the world's largest exporter in terms of phosphate fertilizer production in addition to meeting its own needs. In the past 10 years, its phosphate ore resources account for more than 18% of the world's total phosphate fertilizer exports. For China, phosphate ore resources consumption speed is fast, its resource situation is not optimistic.

Abstract:Manganese is widely used, 90%~95% of the world's manganese is used in the metallurgical industry, the rest in the battery industry, ceramic industry, chemical industry and so on. According to the characteristics of ore-bearing rocks in the process of mineralization, the world manganese deposits are divided into five types, including marine sedimentary type, volcanic (hydrothermal)-sedimentary type, metamorphic type, hydrothermal type and supergene type, with marine sedimentary type, metamorphic type and supergene type as the main ones. By the end of 2019, the worldwide manganese reserves had reached up to 812 million tons, but their distribution is extremely uneven, mainly concentrated in South Africa, Brazil, Ukraine, Australia, Gabon, China, India, Ghana and so on, while the high quality manganese ores are mainly distributed in South Africa, Australia, Gabon and Ghana. The mineralization epoch of manganese can be divided into 7 periods, of which Proterozoic and Cenozoic are of great importance. Manganese deposits are spatially concentrated in the Transvaal Supergroup of South Africa, the Nikopol ore Basin in Ukraine, the Groote Eylandt and Pilbara Craton of Australia, the Pan-Yangtze area of China, the West African Craton. At present, manganese ore production is mainly concentrated in Kalahari and Postmasburg ore fields in South Africa, Groote Island in Australia, Moanda mine in Gabon and Nsuta mine in Ghana.

Abstract:Basins along West African coast have certain similarities in structure and evolution since they have all experienced prerift, rift and drift period, but there also exist differences in present tectonic and sedimentary patterns due to the influence of local events, which leads to different exploration results. In order to summarize characteristics of these basins, the authors compared the comprehensive lithologic column diagrams and restored balanced cross-sections of Niger delta basin and lower Congo basin. The results are as follows. 1) Basins in the equatorial segment have transferred from continental facies such as lacustrine facies and fluvial facies to neritic facies, and there exist no salt deposits in this kind of basins. 2) Niger delta basin is characterized by thick Cenozoic Akata Formation, which is a detachment layer and has been deformed under differential load. 3) The salt-bearing basins in central segment experienced a transition period in Aptian stage, within which sedimentary environment transferred from continent to marine environment. The Aptian salt rocks migrated under the differential load and gravity slippage and divided whole basin into three domains, i.e., extensional domain, salt diapir and contractional domain. 4) The volcanic type in the southern segment is characterized by intense volcanism and extensive development of SDRs.

Abstract:As the Paleogene Ochirbat salt diapir in the western Kuqa foreland thrust belt is the most typical salt diapir structure in China, it can serves as a natural laboratory for the study of salt structure. Based on previous researches, the methods of field mapping, seismic interpretation, remote sensing images interpretation and InSAR (interferometric synthetic aperture radar) technique were used to analyse the salt karst landform characteristics, formation mechanism and rheological model of the Ochirbat salt diapir. The salt karst landforms are mainly developed on the surface of the salt diapir. Karst caves and gullies can be seen on the weathering surface of the diapir, while rillen karrens and miniature karst peak cluster can be seen on the fresh surface. Further more, collapse structures belonging to salt karst landforms can also be regularly seen in the diapir. The formation of the salt diapir was controlled by many factors, including the thrust fault, the erosion of the overburden, the differential loading and buoyancy, and the evolution process of the diapir can be divided into 4 main stages, including thrust piercement, erosion piercement, active piercement and passive piercement stages. It is summarized that after coming out from the underground, the salt flowed from the core to the periphery of the diapir under the gravity, forming salt glacier, and the seasonal river restricted the salt spreading to east, northeast and north directions, resulting in the asymmetric rheological model of the diapir.

Abstract:As one of the most important Quaternary strata in the middle reach of Yangtze River, the gravel layers within the Yangluo Formation are distributed in the north bank of the Yangtze River at the southern foot of Dabie Mountains. There are two views on the origin of the gravel layers. One view holds that the gravel layers of Yangluo Formation are alluvial sediments of the Ancient Yangtze River, which formed terraces on the north bank of the Yangtze River after later tectonic uplifting. Another view is that they are the alluvial fans at the southern foot of Dabie Mountains. As gravel's morphology records its evolution, the study of its morphology can be used to reconstruct palaeoenvironment. In our project, 25 gravel layer profiles were chosen to select total 2693 gravels for measurement of morphological parameter, including 1377 gravels from 14 profiles in Hengdian Town and 1316 gravels from 11 profiles in Yangluo Town. Zingg classification shows that most gravel is mainly oblong shape, and it is mainly distributed in the transitional and fluvial facies in the Sneed Folk triangle. There is a large amount of schist in the gravel layer. The morphological characteristics of the gravel layer of Yangluo Formation indicate that it is of alluvial-diluvial fan deposits formed by rivers at the southern foot of Dabie Mountains.

Abstract:The Zongwulong tectonic belt (ZTB) is located between the northern Qaidam tectonic belt and the south Qilian orogenic belt and contains Late Paleozoic and Early-Middle Triassic strata. Structural features and geochronology of the Zongwulong ductile shear zone have key implications for the tectonic property of the ZTB. This study integrated field structure, microscopic structure and ⁴⁰Ar/³⁹Ar laser probe analysis. The shear zone strikes ~NEE-SWW and dips at a high angle, with a NWW-SEE trending and W-E stretching lineation, indicating the shear zone as a thrust-slip shear ductile shear. The asymmetric folds, rotating porphyroclast, structural lens and crenulation cleavage can be seen in the field. Mica fish, S-C fabrics, σ type quartz porphy roblasts and quartz wire drawing structure can also be observed under the microscope, indicating that the strike-slip related ductile deformation and mylonitization occurred under low-grade greenschist facies conditions at temperatures of 300℃ -400℃. The highly deformed mylonite schist yielded ⁴⁰Ar/³⁹Ar ages (245.8±1.7)Ma and (238.5±2.6)Ma for muscovite and biotite, respectively, indicating that the shear deformation occurred during the Early-Mid Triassic. Combined with a comprehensive analysis of regional geology and petrology, the authors hold that the age of ductile shear deformation represents the time of Indosinian orogeny in the ZTB. The orogenic activity was probably related to the oblique collision between the South Qilian block and the Oulongbuluke block after the closure of the ocean basin.

Abstract:A large number of Yanshanian andesite and rhyolite rocks are developed in the Zengcheng Geopark in Guangzhou. Due to the lack of detailed petrogeochemical studies, their genesis and the tectonic significance have not been clarified. Therefore, a more systematic analysis was conducted for the whole-rock geochemistry and isotopic geochemistry of these volcanic rocks. The results show that the andesitic rocks are somewhat analogous to the Andes-type volcanic ones, with obviously depleted Nb, Ta, Sr and Ti and low I_sr values (0.70332-0.7144, averaging 0.7092), lower rare earth ΣREE(ΣREE=158.9×10^-6-215.010^-6, averaging 186.8×10^-6), with obvious LREE and HREE differentiation((La/Yb)_N5.06-9.87,averaging7.01)and negative Eu anomalies (δEu=0.80-1.38, averaging 0.94) in the chondrite-normalized REE distribution patterns. The rhyolitic rocks have high potassium contents with significant negative Ba, Sr, P, Eu, Ti anomalies and positive Pb and Yb anomalies. They are characterized by the I_sr values ranging from 0.71393 to 0.73650(averaging 0.72615), lower rare earth ΣREE(ΣREE=93.410^-6-481.510^-6,averaging 285.710^-6)with obvious LREE and HREE fractionation((La/Yb)_N 0.65~9.51,averaging 4.35) and negative Eu anomalies (δEu=0.01-0.03, averaging 0.02) in the chondrite-normalized REE distribution patterns. The whole rock Rb-Sr Isotopic age is 112 ±12 ma. The integrated geochemical studies demonstrate that both the andesitic and rhyolitic magmas are of crust-mantle mixing origin, of which the andesitic magma was mainly originated from the mantle and the rhyolitic one mostly from the crust. The andesite rocks and rhyolitic volcanics were formed under the tectonic background of Pacific plate subduction and collision in early Jurassic and early Cretaceous respectively.

Abstract:The mafic-ultramafic rocks in Paleo-Tethys domain of East Kunlun Mountains are not well documented. In this paper, the authors present petrographical, geochronological, lithogeochemical and Hf isotopic data for the Xiwanggou olivine gabbro located in the eastern section of East Kunlun Mountains, Qinghai Province, with the purpose of constraining its formation age, petrogenesis and tectonic setting and providing new constraints for the Late Paleozoic-Early Mesozoic tectono-magmatic evolution in East Kunlun Mountains. Lithogeochemical studies show that the olivine gabbro, which is of sub-alkaline series, is characterized by low SiO₂ (40.91%-42.14%), low TiO₂ (0.29%-0.39%) and alkali content (K₂O+Na₂O=1.09%-1.36%) but high MgO content (28.18%-30.66%). The m/f ratios range from 5.03 to 5.39, falling into the field of ferrous-ultrabasic rocks. This suite of rocks are enriched in LILE (such as Rb, Th, U and K) and Pb, and relatively depleted in HFSE (such as Nb, P and Ti). The rocks have low REE content, with LREE-rich pattern and slightly negative Eu anomaly (ΣREE=28.1710^-6-30.9510^-6, (La/Yb)_N=3.77-4.98, δEu=0.80-0.95). LA-ICP-MS zircon U-Pb dating indicates that the weighted mean age of olivine gabbro is (264.9±1.2)Ma(n=26, MSWD=0.71), suggesting Middle Permian. Zircon ¹⁷⁶Hf/¹⁷⁷Hf values are in the range of 0.282709-0.283152 with corresponding ε_Hf(t) values of 3.7-19.3. and Lu-Hf single-stage modal ages (T_DM) vary from 135 to 753 Ma with mean age being 414Ma, older than U-Pb age. The authors hold that the parental magma of olivine gabbro was likely derived from the depleted mantle, with the probable addition of fluid-modified lithospheric mantle components, and was contaminated by crustal material. Combined with evolutionary characteristics of regional structures in East Kunlun Mountains, the authors consider that Xiwanggou olivine gabbro was formed during the subduction of Anyemaqen-Paleo-Tethys Ocean, and the northward subduction of Anyemaqen-Paleo-Tethys Ocean started at least in Middle Permian.

Abstract:Zircon U-Pb dating indicates that the granite samples collected from the Kuchuwula-Yingba area of western Inner Mongolia includes the Late Devonian monzonitic granite ((371±2)Ma), Middle Permian K-feldspar granite ((271±1)-(270±1)Ma) and Early Cretaceous monzonitic granite ((133±1)Ma). In combination with the data available, the acidic magmatic activity can be divided into 4 stages:Late Devonian (-371 Ma), Late Carboniferous (313-311 Ma), Early-Middle Permian (282-270 Ma) and Early Cretaceous (133-130 Ma). Geochemically, the Late Devonian monzonitic granites belong to the typical S-type granites, which reflects a post-collisional tectonic setting. On the one hand, these data indicate that magmatic activities occurred before the Carboniferous period in the Zhusileng-Hangwula tectonic zone; on the other hand, they probably exactly reflect the lower limit of the time when Kazakhstan + Tarim + North China plate collided with the Siberian plate. The Middle Permian K-feldspar granites belong to the A-type granites, which reflects a tectonic setting of the crustal extension, having a good correspondence with the strong extension environment of this region in the same period. The geochemical characteristics of the Early Cretaceous monzonitic granites are similar to the features of Late Devonian monzonitic granite, also suggesting a post-collisional tectonic setting in accord with the post-collisional and extensional environment of this region in the same period.

Abstract:The NE-trending Xuanhe granitic mass is the largest Yanshanian-Caledonian complex rock mass in southwestern Fujian, which is exposed in southwestern Fujian Province in the arc form. However, there are still different opinions in the formation age of rock mass and its petrogenetic environment, which restricts the discussion of the tectonic environment of southwestern Fujian. Based on detailed field geological survey, the authors investigated the Xuanhe syenogranites, mainly on the basis of the LA-ICP-MS zircon U-Pb geochronology, petrochemistry and Sr-Nd isotope analysis, and discussed the rock types, magma source and tectonic environment. The Xuanhe granites are mainly composed of syenogranites in the forms of speckle fine grain, oligophyric medium-fine grain, porphyritic fine grain, porphyritic fine coarse grain and porphyritic fine grain. The LA-ICP-MS zircon U-Pb age of four samples from the granites are (424.6±2.8)Ma, (426.7±2.6)Ma, (435.5±2.4)Ma and (447±3.6)Ma respectively, indicating that the formation age of Xuanhe granite is Caledonian instead of Indosinian as previously held. The rocks belong to high-K calc alkaline peraluminous rock series, characterized geochemically by high Si, high K (K₂O>Na₂O), low TiO₂, low FeO and low MgO, with average A/CNK value being 1.23. The rocks are S-type grantie, with the characteristics of high content of rare earth elements, obvious right steeply inclined REE fractionation curve, middle negative Eu anomaly, enrichment of large ion lithophile elements such as K, Rb, Pb and Nd and high field strength elements of Th, U and Ba, and relative depletion of Sr, Nb and Ce. The initial Sr isotope ratios are from 0.71291 to 0.71399, the values of εNd(t) vary from -9.1 to -13.4, and two stage Nd model ages correspond to 1.91-2.27 Ga. It is inferred that the granites were formed by partial melting of crustal material of Mayuan Group metamorphic rocks, being probably a product of intraplate Caledonian orogeny in South China.

Abstract:The Changlingzi plagiogranite porphyry is located in the Xilinhot Late Paleozoic Accretion Complex within the Da Hinggan Mountains. This study is focused on the zircon U -Pb isotopic geochronology, Hf isotopic composition analysis and geochemistry of the Changlingzi plagiogranite porphyry. Zircon crystals from the plagiogranite porphyry yielded weighted average ²⁰⁶Pb/²³⁸U age of (248.1±4.7)Ma. The zircons from this porphyry have positive ε_Hf(t) values from 5.78 to 12.41, with T_DM2(Hf) ages from 914 to 488Ma. The plagiogranite porphyry has high content of SiO₂, Na₂O and Al₂O₃, and low content of TiO₂, MgO and CaO, showing a metaluminous-peraluminouslow-K to calc-alkaline affinity, with LREE enrichment and HREE depletion, suggesting I-type granite. In addition, the plagiogranite porphyry has high Sr and low Y values as well as high Sr/Y ratios (74.5~103.4), indicating that the plagiogranite porphyry belongs to adakite. It is suggested that the plagiogranite porphyry was formed by partial melting of the thickened newborn lower crust. And in Early Triassic, Xing' an-Mongolian orogenic belt was in a collisionorogeny tectonic setting, indicating that the Paleo-Asian Ocean had been closed in this period.

Abstract:The Mogutu granite pluton is emplaced in the southwest Huanggangliang to Ganzhuermiao tin-polymetal metallogenic belt in Southern Da Hinggan Mountains, which is mainly composed of biotite moyite. The genetic type, magmatic source region and diagenetic tectonic setting of the Mogutugranite were studied by U-Pb dating of zircon in LA-ICP-MS and petrogeochemical analysis. Zircon LA-ICP-MS dating of the biotite moyite yields a concordant age of 148.8-152.7Ma, which means that the Mogutu granite pluton was formed in Late Jurassic. The Mogutu granites is characterized by weak peraluminous and alkaline, high content of SiO₂ (73.64%-80.86%), K₂O(2.6%-6.0%), but low content of Al2O₃ (10.57%-13.88%), depletion in P、Ti、Ba、Sr, and enrichment Rb、U、Th. The chondrite-normalized patterns of REE are in seagull forms, with strong negative Eu anomalies, with 0.10 to 0.27 of δEu, and higher zircon saturation temperatures(795-911℃), which indicates that the Mogutu pluton is similar to A-type granite. Therefore, the Moguto granites shows highly fractionated A -type granite affinity. Based on the previous research results, it is inferred that the depth of magma source of Mogutu granite pluton is shallow, the magmatic substance was derived from the crust, and the granite pluton was emplaced in the tectonic setting of crustal extension and thinning more likely related to the closure of the Mongol-Okhotsk tectonic belt.

Abstract:As the origin, evolution and tectonic setting of late Mesozoic volcanic rocks in the Great Hinggan Range volcanic belt have always been controversial, our project carried out geochronology and geochemistry studies of the volcanics in the Zamuting area. LA-ICP-MS zircon U-Pb dating of the he Baiyingaolao Formation volcanic rocks in the Zhamuting area reveals that rhyolite and trachoma were formed at 131.6±1.2 Ma and 126.9±1.5 Ma respectively, which are consistent with the identification results of the animal and plant fossil in the Second Member volcanics of the Baiyingaolao Formation, indicating that the volcanic rocks were formed in the early Cretaceous. The rhyolites and trachyandesites of this region belong to alkali series volcanic rocks, with characteristics of high silicon, rich in alkali, low aluminum, low magnesium and calcium, as well as high FeO^T/(FeO^T+MgO) ratio; the rocks are relatively enriched in the large ion lithophile elements Rb, Th, U and Pb, and have a strong deficit in the high-field strong elements such as Nb, Ta, Ti, P, Ba and Sr; the rhyolitic rocks have the characteristics of A-type granite. The studies on trace elements and rare earth elements indicate that both rhyolite and trachyandesites are derived from the melting of the crust and have the same magmatic source. The Baiyingaolao volcanic rocks were formed in the post-orogenic extensional tectonic environment, which reflects that after the southward subduction of the Mongolia Okhotsk Ocean and the collision and integration of the Eerguna-Xingan landmass, the Da Hinggan Mountains volcanic region began to transform from compression to extensional tectonic system. The upwelling and underplating of asthenosphere mantle caused the partial melting of the lower crust, which led to the eruption of rhyolite. The further melting of residual phases led to large-scale eruption of trachyte.

Abstract:In order to solve the problems of the unclear sedimentary patterns and uncertain control factors of sedimentary evolution of the Middle-Upper Jurassic in the southern margin of the Junggar Basin, the vertical sequence, sand body superposition mode, hydrodynamic conditions, sedimentary system evolution and control factors were analyzed by means of fine dissection of several sections and detailed sedimentary description of outcrops in the field. The research shows that braided river sediments, river sediments and fan delta sediments of Middle-Upper Jurassic were deposited from bottom to top, and the changes in hydrodynamic conditions caused by paleoclimate and tectonic events are the main controlling factors of the sedimentary evolution. Specifically, at the bottom of the Toutunhe Formation, braided river sediments were deposited in a warm and humid paleoclimate, forming a stacking pattern of stacked sand bodies; in the middle, braided-meandering river sediments were deposited when the paleoclimate began to be initially arid, forming tightly superimposed sand bodies; and in its upper part, meandering river deposits were developed and isolated channel sand bodies were formed under the condition of less rainfall and paleoclimate drought. As to the Qigu Formation, seasonal meandering river sediments were deposited under arid paleoclimate conditions; the lateral migration sand bodies were developed when the rainfall was sufficient during the wetting period; and laterally continuous sand bodies were developed during the dry period. The Kalaza Formation fan-delta sediments were deposited under hot and dry paleoclimate and intense tectonic activities. The detrital channel formed a vertical cutting sand body in the delta plain, while its frontier underwater distributary channel formed a lateral cutting sand body.

Abstract:Although the Upper Ordovician Linxiang Formation marl in DD1 well is covered with thick silty mudstone, there is a lack of graptolite fossil, and no Hirnantia limestone marker stratum of the Guanyinqiao Member. Therefore, it is difficult to determine the boundary between Ordovician System and Silurian System by biostratigraphic and petrostratigraphic methods. The analysis of trace elements and REE of silty mudstone in the well DD1 shows that Th, Sr, Y, Th/U, Ce_n, Eu_n, δCe and δEu curves at the middle part of silty mudstone (1288.3m) present sharp abnormal peaks with significantly higher ΣREE content of silty mudstone (1288.3m) than its upper and lower silty mudstone and great right slope of the REE distribution curve. By comparing the elemental geochemistry characteristics of the well DD1 with other O-S boundary in the Yangtze Region, it can be concluded that there exists Guanyinqiao Member of Wufeng Formation in the well DD1, and the thickness of this marker layer is also less than 1 m. The geochemical redox discriminant graph shows that the sedimentary water medium mainly was in weak oxidation environment from the Wufeng period to the early Longmaxi period, and its oxidation was the strongest in the Guanyinqiao period. According to the analysis of sedimentary markers, the evolution process of the sedimentary facies at the O-S transition is as follows:subtidal → intertidal → supertidal → intertidal; in the Guanyinqiao period, the water was the shallowest, and there existed supertidal deposits.

Abstract:In order to further explore the provenance and sedimentatary environment of mud shale in the Mesoproterozoic Hongshuizhuang Formation of northern China, samples were collected from outcrops of the Qinghe section of Honghongzhuang Formation for elementary geochemical testing and analysis. The results show that the sediments were not only from terrigenous clastics but also from marine sediments. The results of Y/Ho and ΣREE relationship diagram analysis show that the source proportion of seawater sediments is 10%-20%. In addition, the distribution pattern of rare earth elements and the Ce and Eu anomalies indicate the involvement of volcanic hydrothermal activity in the sediment source. Mo-EF/U-EF analysis results show that Hongshuizhuang is a sedimentary environment of Marine non-stationary basin, and the evolution of redox conditions in the sedimentary period is as follows:in the period of the Lower Member deposition of Hongshuizhuang Formation, the water body was in a strong reductive anaerobic-sulfurization environment; while, during the period of its Upper Member deposition, the reduction degree of water decreased and the environment was anaerobic. It is concluded that the provenance composition and sedimentary environment evolution of the Honghongzhuang Formation are closely related to the sedimentary tectonic setting.

Abstract:There exist abundant iron ooids at the bottom of the Middle Devonian Yangmaba Formation in the Longmenshan area. In order to analyze the genesis of the iron ooids, their characteristics were studied by means of thin section and scanning electron microscope based on the detailed measurement of the Shiligou Profile in Ganxi village. The analysis results show that there are various types of ooids in Middle Devonian Yangmaba Formation of Longmenshan area. The ooidal cores include four types:quartz clastic particles, crinoid fragments, black hematite and calcite. The outer laminas of ooids can be divided into three types:alternate dark and bright one, uniform-colored one and chlorite-fragmented one. The iron ooids of Middle Devonian Yangmaba Formation in the Longmenshan area have an important significance to the ancient environment. The silty ooids were formed in the open environment nearshore shallow water under oxidation condition, and iron ones and chlorite ones with thin layers were deposited in the relatively closed lagoon and residual ooids beach of shallow seashore.

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract: