Abstract:The key demonstration technology for ecological restoration of five types of ecological environments was explored to protect ecological environment of the Yangtze River, including coastal saline-alkali land, coastal wetland of the Yangtze River, chemical pollution sites along the Yangtze River, heavy metal pollution sites and abandoned mines. Through the construction of "engineering, structure, biology and agronomic improvement" and other key technology systems of coastal saline-alkali land, the real-time dynamic monitoring system of water-salt migration environment in coastal saline-alkali land has been established, and the industrialization of a series of agricultural products such as sea rice, corn and canola has been realized, which effectively serve the high-quality utilization and territorial space planning of coastal saline-alkali land. The comprehensive ecological restoration technology of "habitat optimization, plant selection and diversity control" was proposed for the wetlands along the Yangtze River in Qidong, Jiangsu Province. Three ecological function areas, namely wetland leisure and sightseeing area, wetland biodiversity protection area and wetland tailwater deep purification area, were formed. The restoration results achieved good ecological and social benefits. Some progress and results have been made, including innovation of organic pollution detection technology, identification of underground "hidden" pollution of one typical chemical park, accurate delineation of main pollutants depth, and clarification of aniline nitrobenzene and benzene. The proposed suggestions on deepening pollution remediation have been adopted by the local municipal government and environmental protection departments to effectively support and serve the redevelopment of abandoned organic chemical sites. Develop cadmium-resistant transgenic specific plant materials and highly effective remediation microorganisms were developed to explore the formation of a microbial-plant interaction remediation mode in high-cadmium soil along the Yangtze River, which lay an important foundation for the development of microbial amendments and large-scale remediation in the future. The developed key technologies for ecological restoration of Anning phosphate tailings storage yard in Yunnan and resource utilization and reduction of vanadium titanomagnetite tailings in Panzhihua of Sichuan strongly support ecological protection and restoration of abandoned mines and resource utilization of tailings.

Abstract:Airborne hyperspectral imaging is a fast and non-destructive detection technology, which has the characteristics of high spectral resolution, narrow and multiple bands and combination of spectrum and images. Domestic miniaturized airborne hyperspectral imagers mainly rely on importing, which are expensive. Moreover, it is difficult to import high-performance hyperspectral equipment, which restricts the promotion and popularization of hyperspectral technology in China. With the support of the national major instrument development project and the national key research and development plan, Nanjing Center for China Geological Survey successfully developed the light airborne hyperspectral imaging system SSMap with the push-broom miniaturized imaging spectrometer HMS400/1000 as the core components, and established the airborne hyperspectral remote sensing comprehensive survey technology methods and operation process, as well as formed a set of reliable ground object classification methods and spectrum quantitative inversion models of water and soil pollution. Based on the introduction of the basic principle of airborne hyperspectral imaging technology and the analysis of research status at home and abroad, taking the self-developed airborne hyperspectral imaging system SSMap as an example, combined with the requirements of the ecological environment in the Yangtze River Economic Belt, the operation methods, information extraction and investigation application of aerial hyperspectral remote sensing covering an area of 4500 km² are discussed in detail. Through the demonstration of eco-environmental geological survey in Jiangsu, Anhui, Zhejiang and other regions of the Yangtze River Economic Belt, high quality airborne remote sensing data has been obtained, and a number of important survey results have been obtained. The results show that airborne hyperspectral imaging technology has broad application prospects in ecological environment investigation, water monitoring, land use and land quality evaluation. The home-made airborne hyperspectral imager with independent intellectual property rights reduces the procurement cost, promotes the popularization of airborne hyperspectral technology, serves the national major regional development strategy, and has significant economic and social benefits.

Abstract:The current situation and evolution of water resources in the Guangdong-Hong Kong-Macao Greater Bay Area is crucial to the high-quality development of the region's social economy. The study focuses on the current situation of water resources in the "9 Cities +2 Municipalities" of the Greater Bay Area in recent ten years and its co-evolution trend with social economy. The results show that the present water supply in the Greater Bay Area mainly relies on surface water, and the distribution of water resources is not equilibrated with regional economic development. As the core engine of regional development, Hong Kong, Macao, Shenzhen (extremely short of water) and Guangzhou (severely short of water) have a low per capita water resources. Guangzhou, Foshan, Zhongshan, Dongguan (>80%) and Shenzhen (>40%) have a high degree of water resources development and utilization, and the pressure of water resources supply and demand is large. The synergetic law between the current situation of water resources utilization and social economy in the Greater Bay area, resulted from attribution analysis, indicates that industrial structure influences the water consumption structure and controls the water consumption efficiency. The industrial structure and development trend in the region and the comparative analysis with the bay area in the world verify the "Petty Clark theorem" in the theory of industrial structure. With the continuous economic development of the Greater Bay Area, the industrial structure will be optimized forward, water consumption efficiency will increase, and per capita water consumption will gradually decrease. Meanwhile, the demand for urban public water and domestic water will continue to rise, and the water supply facilities, water quality and water supply security in the Greater Bay Area need to be ensured to meet the future social and economic development demands.

Abstract:It is of great significance to find out the interaction between surface water and groundwater for wetland ecological protection and restoration. A multiply tracers approach including water level monitoring, oxygen and hydrogen isotopes analysis and temperature tracing was used to identify the location, magnitude and depth of surface water leakage to shallow groundwater. As also, a brief study of relationship between reed land and water level and groundwater depth was conducted. The results show that the scope of leakage water is controlled by geological and hydrogeological conditions. The depth is about 20m and the length from lake shore varies spatially. The recharge sources of surrounding shallow groundwater are atmospheric rainfall and surface water, of which the recharge proportion of surface water leakage is 0-90.5%. The leakage rate is from 0.01 to 0.59 mm/d inside the wetland and has a strong relationship with the depth of the shallow aquifer. The less the burial depth, the more conducive to surface water leakage. There was a significant relationship between reed land and the average surface water level from 1976 to 2020. When the surface water level was between 6.3 to 6.8 m, the reed land was the largest. When the water level was less than 6.3 m, the reed land had a positive correlation with it, while the reed land area decreased as the water level was higher than 6.8 m. Groundwater depth had an obvious relationship with surface water level where reeds grew. During the growing season, it showed that groundwater depth was suitable for reeds growth most of the time. In order to prompt reed growth, it is suggested that artificial recharge should be conducted before monsoon season to lower groundwater depth. The conclusions can provide basic supports for water recharge, leakage resisting and eco-environment protecting in the Baiyangdian wetland.

Abstract:Xiongan New Area is rich in geothermal resources and has broad prospects for large-scale development and utilization, which is of great significance to the realization of "green Xiongan". Many scholars have focused their research on geological structure exploration, resource evaluation, crustal stability, etc. However, the study on the possible fault sliding caused by the large-scale development of deep karst thermal storage is weak. On the basis of geomechanical theory and geothermal geological survey, Monte Carlo stochastic simulation method was used to evaluate the characteristics of main faults (strike, dip, slip friction coefficient, etc.) and geostress distribution (pore pressure, maximum/minimum/vertical principal stress magnitude and direction, etc.) in Xiongan New area for quantifying the activation possibility of natural faults under large-scale development and utilization. The results show that the maximum slip trends of proven faults under natural, large-scale recharge and hydraulic fracturing conditions are 0.26, 0.27 and 0.40, respectively. Geothermal development will not cause fault activation. The study establishes confidence in geothermal development and provides support for safe geothermal use in Xiong'an New Area.

Abstract:It is of great significance for analyzing the spatiotemporal variation law of surface evapotranspiration and its driving factors to promote the scientific allocation of regional water resources and to do a good job of ecological water source protection. Based on MOD16 ET remote sensing data, trend analysis and significance test method were adopted to analyze the spatial-temporal variation characteristics of surface evapotranspiration in Sanjiang Plain in recent 20 years. According to Penman-Monteith formula, driving factors related to surface evapotranspiration (ET) were selected to analyze the influence of driving factors on the change of surface evapotranspiration. Ridge regression statistical model was built to analyze the main driving factors of evapotranspiration change and their relative contribution rates. The results show that the interannual fluctuation characteristics of surface evapotranspiration (ET) in the Sanjiang Plain were obvious in recent 20 years, and the overall trend of ET was increasing. ET in 91.53% of the study area shows an increasing trend, and the regional differences of ET distribution decreased year by year. The annual ET shows unimodal periodical variation, and the seasonal difference is obvious. Slope in the study area has a positive effect on ET, while elevation and wind speed have a negative effect. Temperature, sunshine duration, precipitation and NDVI are positively correlated with ET, and precipitation has the most significant correlation with ET. The determination coefficient ^R2 of ridge regression driving analysis model is 0.823, which can effectively explain the relationship between various driving factors and ET. The results of model calculation show that precipitation and vegetation coverage have a great influence on the surface evapotranspiration in Sanjiang Plain and are the main driving forces for the change of surface evapotranspiration.

Abstract:Palaeochannel records the evolution information of regional drainage system structure and sedimentary environment in geological history, which is of great theoretical significance to the restoration of palaeoenvironment and the evolution law of drainage system. Based on a Quaternary borehole (L2) in the paleochannel of the alluvial and diluvial fan of Hutuo River, detailed lithological characteristics, grain size parameters and optical ages, the development periods and sedimentary environment evolution of the paleochannel in the middle of Hutuo River since 150,000 years and its response of climate change was discussed. The results show that the sedimentary environment evolution of the study area is mainly composed of three paleochannel development periods and two river stabilization periods since 150,000 years. It has a good correspondence with the deep-sea oxygen isotope stage and the climate change indicated. The three periods of paleochannel development correspond to the second, fourth and sixth stages of the deep-sea oxygen isotopes, and the cold climate respectively. Two river stabilization periods corresponds to the third and fifth stages of the deep-sea oxygen isotopes, and the warm climate respectively. The third paleochannel (about 151~118 ka) was formed by the combination of tectonic uplift caused by the republican movement 150 thousand years ago and the cold-dry climate during the penultimate glaciation. The second palaeochannel (about 76~36 ka) is the result of intermittent regional tectonic uplift and climate change. And the first palaeochannel (about 26~5 ka) was the result of climate change during the last glacial maximum.

Abstract:Arsenic (As) poses a danger to environmental health, and drinking arsenic-rich groundwater is a key exposure risk for humans. The study on distribution, migration, and enrichment of As in groundwater is an important worldwide environmental and public health problem. Huaihe River Basin is presently defined as a region of high-arsenic groundwater in China. In this study, a typical high arsenic groundwater area in the basin was selected as the natural experimental site to analyze the formation and evolution of high arsenic groundwater through the analysis of groundwater hydrogeochemical data, to trace the source and dissolution of arsenic pollutants, and evaluate the potential pollution risk. The results showed that As and F were the main inorganic chemical substances affecting the water quality in the study area, with concentrations of (5.75±5.42) μg/L and (1.29±0.40) mg/L respectively, the ratio of test samples exceeding the recommended drinking water standards of the World Health Organization by 23% and 31% respectively. According to the hydrochemical diagram and the calculation of mineral saturation indices, the groundwater in the study area underwent evaporation, halite dissolution, and water-rock interaction. The total alkalinity of high-arsenic groundwater ranged mainly between 400 and 700 mg/L, and the hydrogeochemical type was mainly of HCO₃-Na. High-arsenic groundwater was largely affected by evaporation and cation exchange. Arsenic in high-arsenic groundwater derived from the dissolution and release of geogentic arsenic in aquifer. The oxidation dissolution and reduction activation of As-bearing minerals may be the main mechanism of the formation of high arsenic groundwater.

Abstract:As well known, the permeability coefficient of cohesive soil is extremely low, and the transport rate of water and solute in the cohesive soil is slow and time-consuming. Stable isotopes δD and δ¹⁸O data of soil moisture and rainfall of two boreholes (ZK1, ZK2) in Dabie Mountain Area-Jianghan Plain rainfall-soil moisture-groundwater transformation scientific field test site were studied to trace the characteristics of historical infiltration and recharge of cohesive soil. The results show that there's no obvious layer boundary but just a little difference among the 15 m deep cohesive soil, and soil water moves in the way of "piston flow" vertically. The closer relation of rainfalls in summer and autumn to soil moisture in δD and δ¹⁸O value indicates that the main recharge of soil moisture comes from rainfall infiltration in summer and autumn. The δD and δ¹⁸O values of soil water in ZK1 (sampling interval 0.5-2.7 m, depth 15 m) fluctuate periodically with the increase of buried depth, while the δD and δ¹⁸O values of soil water in ZK2 (sampling interval 0.1m, depth 6.2 m) fluctuate stratified with the increase of buried depth. On the basis of determining the rainfall infiltration recharge years corresponding to the 0-6.2 m depth in the cohesive soil layer, based on ¹⁸O isotopes peak displacement method,it is calculated that the vertical migration velocity of rainfall infiltration recharge in the cohesive soil layer is 10.8-15.0 cm/a, and the annual infiltration recharge is 43.1-58.1 mm, accounting for 4.01% of the annual average rainfall. It takes about 130 years for rainfall infiltration to penetrate the thick cohesive soil for groundwater recharge, which means the thick cohesive soil has good antifouling properties. The historical evolution characteristics of soil water infiltration and migration at the air-soil interface and the inter-annual correspondence of soil water recharge are of great significance for groundwater environmental protection, ecological environment improvement, drought and flood disaster prevention and control in Jianghan Plain.

Abstract:Groundwater nitrate pollution is a worldwide water environment problem. The increase of nitrate concentration in groundwater causes the deterioration of water quality, while the increase of its relative contents changes the hydrochemical characteristics of groundwater. NO₃^- becomes one of the main anions in groundwater in some areas, and the name of "NO₃ type water" for this new chemical type of groundwater is gradually accepted by scholars. Based on the analysis of the distribution, characteristics and influencing factors of NO₃ type water in shallow groundwater in plain area of Xiamen City, the significance of NO₃ type water was discussed. The results show that the groundwater in Xiamen has been polluted by nitrate nitrogen. NO₃ type water comprising 36.8% of all 87 samples is mainly distributed in weathered residual plain. The eastern Xiang'an and Tong'an districts have formed a relatively large planar distribution, while the western Jimei and Haicang districts have a small distribution, and the distribution is point-like or local small area. NO₃ type water mainly exists in oxidation deposition environment with low pH, low TDS and low hardness. The weathered residual aquifer's characteristics of acid soil、slow runoff and shallow water table provide favorable environmental conditions for NO₃^- enrichment in groundwater. Human sewage, landfill leachate infiltration and agricultural fertilization are the main sources of nitrate pollution in groundwater. It is suggested to carry out research on groundwater nitrate source identification. According to different sources of pollution, measures such as improving the construction of pollution pipe network, improving toilets in rural areas and scientific fertilization should be taken to prevent and control pollution from the source.

Abstract:Geothermal resources are abundant in the Xiong'an New Area, including Niutuozhen geothermal field, Rongcheng geothermal field and Gaoyang geothermal field. The geothermal resources in this area were developed and utilized earlier, but there is still no unified view on its deep heat source mechanism. In order to study the deep heat source mechanism, deep reflection seismic and long-period magnetotelluric survey were carried out in Xiong'an New Area and its periphery. The deep reflection seismic data and magnetotelluric data of the same section were processed and jointly interpreted. The geological structure and electrical structure in the study area from the surface to the Moho surface were explored. The lower crustal structure has a good corresponding relationship between the deep reflection seismic profile and the magnetotelluric profile. The area of low resistivity corresponds to the existence of a series of reflection events on the deep reflection seismic profile, and the event axis can continue to the Moho surface. The areas of high resistivity correspond to the absence of obvious continuous reflection events on the deep reflection seismic profile. Especially above the Moho surface, there is an approximate "blank area" of seismic reflection. Combined with regional geothermal data, a deep geothermal geological model of the study area was constructed, and the deep geothermal mechanism in the new area was explained. This model is a "dual" heat generation model, and its heat source consists of two parts, the deep mantle heat source and the heat generated by the decay of radioactive elements in the crust. The decay heat of radioactive elements accounts for nearly 30% of the surface heat flow, and the mantle-derived heat flow accounts for about 70% of the surface heat flow. Below Niutuo Town and above the Moho, the lower crust was uplifted due to the upwelling of hot mantle material, and the undercut of mantle-derived magma formed a local thermal anomaly in the lower crust. This thermal anomaly has low-speed and high-conductivity geophysical characteristics. It is considered to be the deep heat source of the Niutuozhen geothermal field and the Rongcheng geothermal field. With regional faults as the heat channel, the terrestrial heat flow is conducted upward from depth and diffused to the top of the Niutuozhen and Rongcheng bulges, which is a source of carbonate reservoirs. The water layer is heated to form a geothermal reservoir; the overlying Neogene sedimentary stratum is a good thermal cap layer.

Abstract:The Jinyang Basin of western Liaoning is the largest Mesozoic basin of the outer Lower Liaohe Basin. The shallow igneous rocks with great thickness and many periods are widely developed in the basin. The original data of seismic exploration has a low signal-to-noise ratio due to influencing of igneous rocks on seismic signal shielding and complex seismic geological conditions in the area. Meanwhile the reflected energy of the underlying strata of the igneous rock is weak, which brings about great challenges for effective imaging of seismic data. Based on the characteristics of the original seismic data, targeted acquisition and processing techniques were used to improve the deep reflection energy and signal-to-noise ratio of the data by low frequency geophone, static correction, pre-stack multi-domain denoising, reflected energy compensation and so on. The pre-stack time migration technique is optimized for final imaging through comparison by multiple high precision velocity modeling and seismic migration imaging techniques. Compared with the previous seismic data, the signal-to-noise ratio and resolution of the seismic section reprocessed by this effective imaging technology are significantly improved, the deep reflection energy is effectively restored, and the underlying strata of the igneous rock have clear reflection signals and clear contact between the strata. In particular, the imaging of the faults and strata with large dipping angle has been significantly improved in resolution, which provides high-quality seismic data for subsequent structural interpretation and exploration potential area evaluation.

Abstract:The organic-rich shale of the Wufeng-Longmaxi Formation in the western Hubei Province has become a hotspot for the shale-gas exploration in South China. In order to deepen the understanding of reservoir characteristics and gas-bearing capacity, the lithological and geochemical characteristics, types and features of reservoir space, and gas-bearing capacity were detailedly studied on the basis of the drilling and testing data of the Well Eyy2, as well as the affecting factors of shale gas and evaluation of shale reservoir. The results show that the organic-rich shale extending to LM7 graptolite zone in the Well Eyy2 is about 16m in thickness and the LM5-LM6 graptolite zone is missing, which is mainly composed of siliceous shale interbedded with silicastone, mixed shale and clay shale. Organic type is type Ⅰ and Ⅱ1, with Ro value ranging from 1.88% to 2.03% indicating that the shale is under massive gas generating stage. The main reservoir space consist of organic nanopores with diameter less than 100 nm, micropores with diameter exceed 5um and tectonic microfracture, of which the volume ratio of nanopore is more than 50%. Pore volume and specific area has closely positive relationship with total organic content (TOC). The on-site measured core gas content ranges from 0.068 to 3.33 m³/t with average of 1.13 m³/t, and the graptolite zone WF2-WF3 in the Katian and LM2-LM4 in the Rhuddanian has highest gas content. Gas content has obviously positive correlation with TOC and brittle mineral content. According to the TOC, gas content, brittle mineral content, shale sedimentary environment and other parameters, the favorable reservoir (typeⅠ) with about 9 m in thickness mainly corresponds to siliceous shale interbedded with silicastone of the graptolite zone WF2-WF3 in the Katian and LM2-LM4 in the Rhuddanian formed in the deep-water sedimentary environment, which is the best "sweet spot" for the horizontal drilling in the shale gas exploration in the Wufeng-Longmaxi Formation.

Abstract:Shale of the Frasnian Shetianqiao Formation in Hunan Province is an important target for shale gas exploration. The Shetianqiao Formation and its multiple coeval strata characterized by regional rapid lithofacies differentiation lead easily to confusion in quotation and difficulty in outcrop identification, which restrict its shale gas exploration process. By clarifying the historical evolution of Shetianqiao Formation and its corresponding strata, their distribution area and application area were defined and delineated. Based on the variation of rock assemblage, organic carbon and existing exploration results of the Shetianqiao Formation, it is proposed that the Xinhua-Lianyuan and Shaodong region with higher inputing of terrestrial detritus are the favorable prospects for shale gas exploration, and exactly locating the range of inter-platform basin in carbonate platform is the key role for further shale gas exploration.

Abstract:With the continuous discoveries of commercial Proterozoic primary reservoirs in recent years, Proterozoic strata have gradually become the focus of oil and gas exploration. Yanshan area of North China Platform is one of the most developed regions of the Meso-Neoproterozoic stratum in China, and the thickness of the Meso-Neoproterozoic can reach 9553 m. Although oil and gas shows such as oil seedlings were discovered long ago, the exploration breakthrough of oil and gas has not been made so far. In order to carry out targeted oil and gas investigation and exploration, it is of great significance to select the favorable source rock for oil and gas exploration from the Meso-Neoproterozoic sedimentary strata. Based on the analysis of sedimentary characteristics of dark mudstone and microbial carbonate rocks of Meso-Proterozoic in North China Platform, the hydrocarbon generating potential was preliminarily evaluated. The average values of TOC for thick dark mudstones or shales developed in Chuanliggou Formation, Honghongzhuang Formation and Xiamaling Formation are 0.89%, 2.54% and 2.82%, respectively, and the average values of Ro are 2.03%,1.05% and 0.63%, respectively. Microbial carbonate rocks are widely developed in Gaoyuzhuang Formation, Wumishan Formation and Tieling Formation, rich in microbial community and other organic matter residues, in which high quality source rock with TOC > 0.2% are developed.

Abstract:Located in the north-central part of the Fogang complex pluton, the Xinping Cu-Mo mineralization granodiorite pluton formed in late Early Cretaceous, and its LA-ICP-MS zircon U-Pb age is (104.6±1.8)Ma(MSWD=1.2). The granodiorite is characterized by medium acidity (SiO₂=63.43%-65.27%), quasi-aluminium(ACNK=0.76-0.92), medium alkali(ALK=6.09%-7.63%) and high-K Calc-alkaline. It shows enrichment in light rare earth elements Rb, U, Th and La, and the ratio of LREE/HREE is 8.26-13.20 while (La/Yb)_N is 8.17-16.64. Otherwise, it shows depletion in Nb, Ta, Ti, P, Ba and Sr, with minor loss of Eu (δEu=0.73-0.87). The ε_Hf(t) range from -3.0 to +0.2, and the two-stage model age of Hf(t_DM2) is 1.16-1.36Ga, and the index of Mg(Mg^#) is 42.64-46.95. All of these indicate that the source rocks are mainly crustal materials formed in Mesoproterozoic, with the participation of deficient mantle components. The ratio of Nb/U and Nb/La is respectively 0.20-0.38 and 1.7-2.2, which indicates that the source area is affected by the fluid metasomatism in subduction of Paleo-Pacific Plate. This study shows that the Xinping granodiorite is dominated by partial melting in process of diageneesis. The Xinping pluton formed in the extensional setting under the subduction of the Paleo-Pacific plate in late Yanshanian period, which is related to the partial melting of the Mesoproterozoic crystalline basement induced by the basaltic magma. In late Early Cretaceous, it was an important Cu-Au-Mo mineralization period in late Mesozoic in southeastern China, while the Xinping granodiorite, located in the middle east of Nanling mountains, coincide with the diagenetic age of the Zijinshan copper polymetallic rocks or ores in the southwestern Fujian Province, with similar petrochemical characteristics. Also, the obvious copper-molybdenum mineralization can be observed in the field, so it will have a good prospecting prospect for copper-molybdenum deposits.

Abstract:The Miaoershan pluton, located at the junction of southwestern Hunan and Northern Guangxi, is a composite batholith composed of Jinningian, Caledonian, Indosinian and Yanshanian granites. Among them, Caledonian granites constitute the main body of the composite batholith, which can be divided into six intruding episodes. Through zircon LA-ICP-MS dating, the ages of the first, second and sixth episodic granites were measured at (428.1±3.6) Ma, (420.3±3.4)-(421.3±3.2) Ma and (408.3±3.5) Ma, respectively. The average (⁸⁷Sr/⁸⁶Sr)_i, ε_Nd(t) and the δ¹⁸O values of the Caledonian granites are 0.71765, -9.7, and 9.8, respectively. Caledonian granites are generally crust derived weak peraluminous-strong peraluminous granites, formed in post-collisional tectonic environment characterized by weakened compression and relaxed stress after the peak period of collision and extrusion. Their material and heat sources are different in the early and late stages. The early stage granites were derived from upper crustal metamorphic mudstone, psammite and/or metamorphic igneous rocks, and their formation temperature is relatively high(> 875℃). The late stage granites were derived from upper crustal metamorphic mudstone with lower formation temperature (< 875℃), showing the characteristics of typical S-type granites.

Abstract:In order to explore the magmatic origin and tectonic setting of the Jiuling pluton in northern Jiangxi, a combined study of geochronology, geochemistry and zircon Lu-Hf isotope was carried out for the Dahutang biotite granodiorite. LA-ICP-MS zircon U-Pb dating of biotite granodiorite suggests it was formed at (835.6±1.5) Ma. Geochemistry analysis shows it belongs to the series of potassium-high potassium calcium alkaline peraluminous granite. It has the typical characteristics of S-type granite and it was derived from the melting of the Neoproterozoic Shuangqiaoshan Group. The positive zircon ε_Hf (t) value (2.8-8.2) suggests that the magma forming the granite was originated from the recycling of Proterozoic crustal material. The Dahutang biotite granodiorite was formed in a tectonic background of transition stage from syn-collision to post-collision. Combining with previous studies, it is inferred that that the upper time limit of collision between the Yangtze and Cathaysia plate should be about 835 Ma.

Abstract:Dongkengkou acid pluton in northeast Jiangxi Province was selected as a study case to expound its petrography, chronology, zircon Hf isotopes and petrogeochemistry. The LA-ICP-MS zircon U-Pb dating of granite porphyry and granodiorite porphyry yields ages of (134.25±0.99)Ma and(132.6±1.3)Ma respectively, indicating that the Dongkengkou pluton was emplaced during the late Yanshanian. The main element geochemical characteristics of Donggangkou acidic pluton are basically the same. They are all high-k calc-alkaline granites with high SiO₂ content and aluminum saturation index A/CNK values less than 1.1, which belong to typical I-type granite. The pluton is enriched in large ion lithophile elements such as Rb, Th and U, depleted in high field strength elements such as Ti and P, and slightly depleted in Ba and Sr. The characteristics of rare earth elements in acidic rocks are consistent, but Eu deficit is not obvious. Combined with Hf isotopes, it is indicated that the magma of the pluton was formed by the partial melting of metamorphic sandstone from the lower crust. It has typical characteristics of adakite rocks with low Mg. It is inferred that the pluton was formed during the transformation from crust thickening due to collision and compression to crust thinning due to extension in the process of continent-continent collision. The tectonic environment is intracontinental orogen. The subduction of the Pacific plate to the South China Continent results in the back-arc multi-stage lithospheric extension.

Abstract:The Wenquan Mo ore deposit, the only one porphyry-type Mo deposit in the West Qinling, is located on the northern margin of the West Qinling orogenic belt. The ore bodies are mainly distributed within the granite porphyry and the contact zone between the granite porphyry and its surrounding rocks. The zircon U-Pb dating and Hf isotope studying of the ore deposit have great significance to define the forming age of the granite porphyry, reveal the evolution of the magma, and furthermore to clarify genesis of the ore deposit. The zircon LA-ICP MS U-Pb dating method was used to constrain the forming age of Mo-bearing granite porphyry in the Wenquan mine. Zircons from the granite porphyry have clear zonal texture and large value of Th/U ratio (0.41~0.88). The LA-ICPMS U-Pb dating of zircons from the Mo-bearing granite porphyry and its intruding porphyritic monzogranite yield ages of 212.43~213.4Ma and 219.9Ma respectively, indicating Late Triassic magmatic product. The hafnium isotope of the granite porphyry has a negative value between -1.89 and -1.63, with an average value of -1.59. On the ε_Hf(t)-t diagram, the sampling points are plotted below the chondrite and the deficit mantle line, which indicates a unitary magmatic source. This source is the partially melting product of the modified earth crust. The age of the second stage (T_DM2) model ranges from 1291 to 1408 Ma, which indicates that the magma was probably derived from the partiall melting of Mesoproterozoic earth crust.

Abstract:Large area of monzogranite is outcropped in the Hansumu area of southern Great Khingan. In order to recognize the formation age of the rock and its tectonic significance, samples were collected from the monzogranite pluton to study its petrography, zircon LA-MC-ICP-MS age and Hf isotope. The results show that the pluton is composed of fine-grained porphyritic amphibolit-biotite monzogranite and fine-grained porphyritic biotite monzogranite with porphyritic and porphyritic structures and massive structures. The zircons from the monzogranite is of magmatic origin, and yields ²⁰⁶Pb/²³⁸U age of 136±1 Ma (MSWD=1.4), which suggests that the pluton was formed in the late Early Cretaceous. This result is strongly consistent with the study area and its surrounding areas, and even with the 114-145 Ma magmatic activities in the northeastern of China, indicating the products of the same magmatic activity stage. The monzogranite in the Hansumu area has positive ε_Hf (t) values of 7.1 to 14.4 and young Hf two-stage model ages, and T_DM2 is 324 to 959 Ma. Young Hf isotope model ages imply that this area could have experienced an important crustal accretion event during the Neoproterozoic-Late Proterozoic. Combined with regional geology, it is suggested that the monzogranite was likely derived from the partial melting of young mantle, and possibly was formed in a lithosphere extensional tectonics environment related to the subduction of the Paleo-Asian plate to Eurasia Plate.

Abstract:The petrological, zircon U-Pb dating, whole-rock geochemical, and zircon Hf isotopic data of the Early Cretaceous andesites and dacites in the Maqianxiang area of Baingoin County, Tibet, are reported. The zircon U-Pb ages of andesite are (108.0±1.5)Ma and (113.6±0.9) Ma, and those of dacite are (106.7±1.9) Ma and (113.6±0.8) Ma. The andesites are enriched in Th and U and depleted in Nb, Ta, and Ti, have variable Mg^# values (25-63), and show mainly negative zircon ε_Hf(t) values (-8.6 to +1.5). They are probably generated by mixing of mantle- and crust-derived melts. Dacite shares similar trace element features with the coeval andesite, and has negative zircon ε_Hf(t) values (-12.3 to -8.1). It is interpreted as a product of partially melting crust. The andesite and dacite are interpreted as a product of the ca.110 Ma magmatism along the Bangong-Nujiang suture zone, and may be related to the continent-continent collision process after the closure of the Bangong-Nujiang Ocean.

Abstract:The gently dipping ductile shear zone widely distributed in the Zhan baling uplift is obviously different from the steeply dipping ductile shear zone formed by the translation of the Tanlu fault. Based on the geometry and kinematics analysis of gently dipping ductile shear zone, combined with the characteristics of the Early Cretaceous basins and the isotopic dating of extensional detachment faults and syntectonic magmatic rocks of the metamorphic core complexes in eastern China, the Early Cretaceous metamorphic core complex of Zhangbaling uplift is defined. Its upper plate is composed of the Nanhua-Ordovician sedimentary strata and the Early Cretaceous sediments, the lower plate is composed of Neoproterozoic metamorphic clastic sedimentary rocks, metamarine volcanic rocks (basement) and early Cretaceous intrusive rocks. The upper and lower plates are separated by a main extensional detachment fault. The long axis of the metamorphic core complex is NE-SW, with indicative structure reflecting shear slipping to SE of the upper plate, which is completely consistent with the extension direction of the metamorphic core complex in eastern China. Through the determination of the metamorphic core complex, combined with field geological facts, it is believed that the Guandian-Machang fault is a secondary fault of Tanlu fault, which is a response to the third left-lateral translation of Tanlu fault zone at the end of Early Cretaceous. On the basis of comprehensive research, a regional tectonic-magmatic-metallogenic relationship model is established, which revealing that the Zhangbaling uplift has undergone three tectonic stages during early Cretaceous:Early extension(metamorphic core complex stage)-compression strike-slip (Guandian-Machang fault formation stage)-late extension (dioritic dike emplacement stage). The superimposition of multi-stage structuring and magmatism results in the formation of gold polymetallic minerals deposits in this area.

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