Abstract:A large-scale glacial/rock fall occurred in the upstream of Sedongpu basin on the left bank of the Yarlung Zangbo River in Linzhi of Tibet on October 17, 2018. The runout materials were composed of glaciers and rocks, which impacted the accumulation and moraine of the lower part, then formed a debris flow and dammed the Yarlung Zangbo River impounding a barrier lake. This study aims to identify the triggering mechanisms and propose a theoretical basis for the development of landslide hazard prevention and reduction. In this paper, the authors adopted short distance observation by helicopter, statistical analysis of climate change data, interpretation of multi-temporal satellite remote images, calculation of landslide-debris flow velocity using the Scheidegger formula and the b value of seismic activity sequence calculated by Gutenberg-Richter formula as well as multi-factor assignment statistics to evaluate the site and scale of the future glacial falls. It was found that the debris flow was triggered under the condition of high and steep terrain, broken rock mass, climate warming, regional rainfall, glacier ablation, fracture activity and earthquake damage (b value being about 0.7). The volume of the deposition materials was estimated at 31×10⁶ m³ (including previous residual accumulation), which were mainly composed of gravel soil, a small amount of ice and big boulder. The whole event lasted 6.7 minutes with an average movement speed of about 20 m/s. The runout distance of the landslide was more than 8 km. Two-thirds of the Yarlung Zangbo River had been blocked before the glacial/rock fall-landslide-debris flow event that occurred on October 17, 2018. The countermeasures of disaster prevention and reduction which include adaption to the nature, comprehensive avoidance and reasonable dredging are put forward in consideration of the reality of high and steep hillslope, sparse population and traffic inconvenience in this area. The Sedongpu event that occurred on October 17, 2018 was a typical cascading landslide hazard, with a process of landslide-debris flow-dammed lake-outburst flood disaster. Such events will continue to occur frequently for a long time in the future. Based on a comprehensive analysis, the authors have reached the conclusion that a new landslide-debris flow-dammed lake event will be triggered again when the average temperature exceeds 13℃, or precipitation exceeds 5 mm/h or 10mm/d, or the earthquake PGA is greater than 0.18g.

Abstract:Groundwater is an important drinking water source in Southwest China. However, there exists a large area of sulfate exceeding standard in groundwater in the northern part of Zhenning County in Central Guizhou Province, which leads to the problem of water shortage in local area. The following conclusions were obtained by methods of lithofacies palaeogeographic analysis, hydrochemical analysis, D, ¹⁸O, ³⁴S isotope test, rock sample test, core observation and other technical methods:The main source of water supply in the study area is meteoric water; the concentration of sulfate (SO₄^2-) in groundwater is in the range of 30-1100 mg/L, with an average value of 221.78 mg/L, showing the characteristics of highly enriched S0₄^2-; the concentration of S0₄^2- in different types of groundwater exhibits the law of well > rising spring > falling spring > karst pool > underground river > bedrock fissure spring > epikarst spring; the source of sulfate root in epikarst spring is mainly meteoric water, and the source of sulfate root in high sulfate samples such as J469, J585, ZK3-2 and C010 is mainly dissolved in gypsum. On such a basis and in combination with drilling data, the authors detected the distribution of gypsum rock layer and the characteristics of aquifer structure, and adopted the lower sulfate aquifers to obtain qualified drinking water source by establishing the "cross layer water finding" model, which can effectively solve the problem of water shortage in the study area.

Abstract:The three-dimensional (3D) geological structure model has been the basic preconditions for the analysis of urban underground space, because it can directly display the spatial distribution and geological properties of superficial deposits and provide basic data for the scientific planning of the underground space resources. In this paper, the authors constructed for the very first time a 3D geological structure model (up to the depth of 50m from the surface) in Beijing City, based on almost a thousand boreholes, investigation reports, as well as 107 intersecting cross-sections arranged over Beijing City within the 5th Ring Road. The authors investigated the 3D modeling procedures in the study area, where an extremely complicated sedimentary environment is developed with various geological phenomena including intersecting stratigraphic interfaces, missing strata as well as discontinuous layers. The resulting 3D model could provide a basic framework and data support for further geological evaluation of underground space resources.

Abstract:As a renewable clean energy, geothermal resources play an important role in sustainable development. As the sedimentary basin type geothermal resources are mostly distributed in the population gathering areas such as the plain basin, it is important to study the geothermal resources of the sedimentary basin. Based on the analysis of geothermal reservoir distribution and hydrochemical characteristics of sedimentary basins in China, the authors evaluated the geothermal resources of sedimentary basins. The geothermal resources of sedimentary basins are mainly medium and low temperature geothermal resources, and they constitute the main type of geothermal resources in China, accounting for 89% of the total geothermal resources. Moreover, they have the characteristics of wide reservoir space, large thickness, abundant types of geothermal resources, large reserves of geothermal resources, medium and low temperature geothermal water and high availability of resources. The chemical types of geothermal water in sedimentary basin type generally change from low-mineralized water such as HCO₃-Na and HCO₃-Cl-Na through ClHCO₃-Na type and to high-mineralized water such as Cl-Na type in drainage area or closure state. The salinity increases from shallow to deep part as well. The thermal resources in thermal basins account for 54% of the total reserves in major sedimentary basins, 59% of the total recoverable reserves in major sedimentary basins, 42% in warm basins, 40% in recoverable reserves, 4% in cold basins and 1% in recoverable reserves. Therefore, geothermal resources exploration should be further strengthened, geothermal resources recharge should be actively carried out to ensure sustainable development and utilization, geothermal resources comprehensive utilization should be promoted, and geothermal resources monitoring network should be established.

Abstract:In order to study the characteristics of subsidence and the difference between each tectonic unit and time as well as its affecting factors in Pearl River Mouth Basin, the authors chose 32 simulation wells to calculate the subsidence and to make comprehensive analysis, and selected 12 typical wells from 32 simulation wells to make contrastive analysis. In the meantime, 3 typically evolution sections were also analyzed comprehensively. According to the results obtained, the overall subsidence can be divided into three episodes:the first episode was Eocene, whose average overall subsidence rate was 85m/myr; the second episode was from Oligocene to Middle Miocene, whose average overall subsidence rate was 146m/myr; the third episode was from Late Miocene to Quaternary, whose average overall subsidence rate was 104m/myr. The subsidence and evolution characteristics of various tectonic units were different during the same period, and the characteristics of subsidence and evolution in the same unit were also varied during different periods. The subsidence rate on the same plane can be arranged into different zones. The diversity in the changes during the subsidence evolution was affected by tectonic evolution stages of the basin as well as the structural characteristics. The characteristics of overall subsidence were controlled by basin dynamics, whereas the differences of subsidence were controlled by dynamics and structural framework. The overall subsidence can be divided into several episodes in Pearl River Mouth Basin. The characteristics of subsidence and evolution were varied between different time and space spans. Both of the basin dynamics and structural framework controlled the features of subsidence.

Abstract:In the groundwater contamination research, molecular biotechnologies are one of the cutting-edge technologies. This kind of technologies have been commonly used at site scale, but rarely applied at regional scale. The shallow groundwater in Hutuo River Basin was selected as the study subject, because of it is one of the typical regions in front of the Taihang Mountains. 67 samples were collected along the river. The 16s rDNA gene sequences were tested by high-throughput sequencing technology. According to the environmental factors of NO₃^-, COD and TDS, the microbial communities and the functional indicator microorganisms related to groundwater contamination were studied. The results showed that, using the cumulative probability distribution method, the samples were divided into three groups:background (B group), nitrate pollution (N group), and organic pollution (Y group). This grouping rule was close to the Ⅲ water grade threshold in the quality standard of groundwater. The order of microbial community richness is B group > N group > Y group. The organic pollution could decrease the richness diversity of microbial communities, and the difference was more significant in comparison with background microorganisms. The functional indicator microorganisms related to organic pollution was Acinetobacter, and the functional indicator microorganisms related to nitrate pollution was Nitrospira. The molecular biotechnologies and analysis methods used in this research could provide the theoretical evidence for regional environmental investigation and bioremediation.

Abstract:To explore the characteristics, sources and main controlling factors of water chemical ions in surface or groundwater of Poxin underground river system and the implications of carbon stable isotope, the authors collected hydrochemical and carbon stable isotopic data from 38 water sites in the Poxin underground river basin and did analysis with stoichiometry and isotopic method. The results show that spatially, the chemical ions in the mainstream of underground river vary significantly due to the effect of the regional rock types and the dilution of the tributaries. Ion proportional analysis shows that the precipitation has great influence on Cl^- and Na⁺ in some springs, and the main type of carbonate dissolution seems to be limestone in the study area. The Mg²⁺/Ca²⁺ molar ratios of surface water and water in ground river skylight are negatively correlated with HCO₃^-, indicating that,at the macroscopic scale, the dissolution will become more intense with the higher HCO₃^- value, and H₂SO₄ and HNO₃ will participate during the weathering of carbonate rocks actively. Silicate rocks weathering has contributed to Ca²⁺, Mg²⁺, Na⁺ and K⁺ of surface water and groundwater. Mining activities and agricultural activities have a great impact on the generation of SO₄^2- and NO₃^-. The forward model of mass balance shows that, owing to regional rock types and hydrological conditions, water in surface and underground river skylights is mainly dominated by carbonate dissolution, whereas silicate dissolution and atmospheric input also contribute some components, and hence the ratios of three sources vary greatly spatially. The dissolved inorganic carbon (DIC) in the water is mainly derived from the dissolution of carbonate rocks and the soil CO₂. DIC and the δ¹³C_DIC values are obviously different between surface water and groundwater, and are negatively correlated with δ¹³C_DIC, implying that the more DIC from the soil CO₂, the more intense the dissolution capacity of the carbonate minerals. Based on the data from this study area and previous study in upper, middle and lower reaches of Xijiang River, the authors detected that both of data support the argument that the aquatic algae can apply DIC transport to organic carbon, and forms a stable carbon sink.

Abstract:Using data of 5 drill holes of the Dawenkou and the Zhujiagou Formation, combined with data from 55 drill holes obtained in hydrogeology survey, the authors studied the characteristics of distribution, physical properties, water-bearing condition, hydrochemistry and groundwater recharge cycle of the Paleogene water-bearing formation in the middle and upper reaches of the Dawenhe River basin. The results show that the watery upper section of Dawenkou Formation is distributed in the north of the basin. The lithology of the aquifer is semi-consolidated conglomerate with HCO₃-Ca·Mg type. The Zhujiagou Formation is distributed in the depression plate of boundary faults, with good dissolution calcareous conglomerate aquifer media and complex hydrochemical types. Modern precipitation is the main source of groundwater recharge. Evaporation and concentration, dissolution of calcite, dolomite and gypsum and polluting activities have participated in the formation of hydrochemical components. This paper sums up 3 groundwater enrichment patterns of different Paleogene water-bearing formations:water controlled by structural fractures, fracture and pore water enrichment in semi-consolidated water-bearing formation, and fractured karst water enrichment in calcareous conglomerate.

Abstract:The age structure of aquifer is an important basis for understanding the sustainability of groundwater exploitation. Increasing groundwater pumping with deteriorate groundwater environment in the Muling-Xingkai Plain (MXP) has restricted to some extent the sustainable development of the region. 31 groups of CFCs and 60 groups of ³H samples were collected to delineate groundwater flow systems. Estimated groundwater age ranges from 21 years to more than 70 years in the northern part of the MXP. Younger water occurs in northwest piedmont and hilly areas as well as Muling River, while older water occurs in the central part of the plain and the Wusuli River. This reflects long flow paths associated with regional flow. Although groundwater is mainly recharged by rain and surface water, ground water younger than 10 years was not found for the unsaturated zone consisting of silty clay. The variations of ³H and CFCs combined NO₃^- with wells depth indicate that the aquifer sensitivity of groundwater system above 60m is low and it is high below 100m. Wells for drinking water should exceed 100m.

Abstract:For the purpose of understanding the age, hydrochemical characteristics and evolution of groundwater in Taiyuan Formation limestone aquifer in the Huaibei coalfield, twenty nine groundwater samples were collected from the Huaibei coalfield, and concentrations of major ions, hydrogen and oxygen isotopes and ¹⁴C radio isotopes were analyzed. The traditional graphic and statistical methods were used to discuss the evolution of groundwater and hydrochemical characteristics as well as the age and runoff characteristics of groundwater. Some conclusions have been reached:the ages of groundwater samples in Taiyuan Formation limestone aquifer vary from 2900a to 21920a, the hydrochemical characteristics of groundwater are different in different mining areas. The groundwater samples in the Zhahe mining area have lower TDS concentrations, the minimum age and the highest values of δD and δ¹⁸O, and hence this area could be regarded as the recharge area in the Huaibei coalfield. The groundwater samples in the Suntuan mine and Taoyuan mine have largest age, higher concentrations of TDS and lower δD and δ¹⁸O values, and such areas could be considered to be the drainage areas. The contour diagrams about TDS concentrations and groundwater age show consistent patterns, suggesting that the main recharge area of groundwater in Taiyuan Formation limestone aquifers lies in the northeast area of the Huaibei coalfield. The groundwater runoff characteristics in Taiyuan Formation are mainly controlled by the tectonic setting, and the recharge conditions and water-rock interaction degrees of groundwater are main factors for the concentrations of TDS and hydrogen and oxygen isotopes.

Abstract:In order to investigate the features of strata configuration and fault structure and study the karst water flow path in Yuquanshan area of western Beijing, the authors carried out integrated geophysical survey in the surrounding area of Yuquanshan and completed regional gravity survey 107 km² in area with 3670 measurement points. On the basis of the explanation of gravity anomaly, 5.1km controlled source audio-frequency magnetotellurics (CSAMT) profiles and 4 microtremor measurement points were carried out. According to these geophysical data, the basement relief and structure distribution were comprehensively studied, and 10 possible faults were interpreted and deduced. Combined with regional hydrogeological data, the hydrogeological significance of the main faults was studied. Then a new understanding of the strong karst water flow path in Yuquanshan area was obtained, which is consistent with the result of the latest isotope and hydrochemistry studies. This study provides the geophysical support for determining a reasonable recharge program for the restoration of Yuquanshan spring.

Abstract:Through studying the changes for meteorological factors, runoff and land cover in Golmud and Delingha in Qaidam Basin, it is found that the water resources and environment has been influenced significantly by climatic warm-wet situation in the-Tibetan Plateau. In the study area, the temperature increases significantly, the drought index decreases significantly, and the climatic warm-wet situation is significant. From 2000 to 2016, the annual average temperature increased respectively 1.7℃ and 1.3℃, annual average precipitation increased respectively 2 mm and 63 mm, annual average runoff increased respectively 240×10⁶ and 90×10⁶ m³, compared with 1960-1999, in Golmud and Delingha basin. From 2000 to 2012, the bare land in the whole basin decreased, the area of grassland, permanent ice, snow, water area and open shrub increased, and ecological vegetation was developed very well. The climatic warm-wet situation promotes the increase in precipitation, and it is the main reason for the increase of runoff, water resources, as well as the improvement of ecological environment. At the present stage, the warm-wet environment is beneficial to water resources development and ecological environmental protection in Qaidam Basin; nevertheless, the sustainable development of the water resources and environment needs further monitoring and deep research.

Abstract:The integrated surface-groundwater model based on physical processes can comprehensively and systematically describe the water cycle process of the basin and provide detailed information for water resources management. At the same time, the future trends of water resources are significantly affected by climate change, and the problem as to how water resources change in future climate scenarios will affect water management measures. The authors evaluated the regional water resources response to climate change, based on the surface water-groundwater coupling model GSFLOW. By predicting the regional water resources change trend under the future climate scenario (CMIP5), the results can provide reference of water resources management for the arid regions. Some conclusions have been reached:(1) The GSFLOW model can simulate the complex water cycle of the middle reaches of the Heihe River. (2) Under the medium stabilization scenario (RCP4.5), precipitation in the region increases by an average of 0.6 mm per year, with an average temperature increase of 0.03 degrees Celsius per year, surface water flow of an average of 1.5 billion cubic meters per year, and groundwater reserves decreasing by an average of 38 million cubic meters per year. Under the high radioactive forcing scenario (RCP8.5), the average precipitation increases by 0.8 mm per year, the average temperature increases by 0.06 degrees Celsius per year, the surface water flow is 1.37 billion cubic meters per year, and the groundwater reserves decrease by an average of 34 million cubic meters per year.

Abstract:As a typical steep stratified oblique rock slope, Shanyang rockslide in Shaanxi Province is different from buckling failure of inclination-paralleled rockslide, apparent dip slide of inclined bedding rockslide and, what is more, toppling and sliding of steeply inclined rockslide,and belongs to the apparent dip creep-buckling. On the basis of field investigation and analysis of characteristics of structure planes, structure of sliding rockmass and shear outlet, the authors analyzed the failure mode in combination with the buckling mechanism. The authors established and analyzed the buckling mechanical model of steep stratified oblique rock slope under gravity, hydrostatic pressure of groundwater, lateral friction and rockmass depth of the rockslide according to the beam plate theory and mechanical model of bending-buckling failure of slab rent structure rockmass, as well as the condition equation of buckling length. The validity of the condition equation was verified.

Abstract:The urban area of Xuzhou has had serious karst collapse geological hazards which are widely distributed in the old Yellow River fault zone. There exists obvious regularity that the karst collapses are caused by excessive groundwater exploitation, and the fault zone is enriched with groundwater. The research shows that the karst is developed well in the old Yellow River fault zone and there are upward opening karst caves and fissure. The fault zone has linked up aquifers of different ages and thus has formed fierce runoff belt or enrichment belt of groundwater. The graben fault zone constituted negative landforms which formed the late Pleistocene and Holocene paleochannels. The paleochannels become "permeable-only covering layer" and "permeable-aquiclude covering layer" which made the sandy soil of the Yellow River flood sediments directly cover the karst aquifers. Then they provided important hydrodynamic conditions for the karst collapse which was caused by excessive groundwater exploitation. Therefore the extensional-shear fault zone and the accompanying fractures have controlled the formation conditions of karst collapses, especially karst development, karst hydrogeological structure and enrichment regularity of groundwater.

Abstract:The genetic mechanism of dolomite of the Middle Jurassic Buqu Formation in the Qiangtang depression was studied by using microscopy, fluid Inclusion data, and carbon and oxygen isotope analysis. The results show that the dolomites in the study area can be divided into fine-powdery dolomite, medium dolomite and coarse dolomite according to grain size. Dolomite generally has a fogged center and clear margin structure, in the cracks near the extensive development of grained saddle dolomite. Fluid inclusions in the dolomite have homogenization temperature ranging between 150.2 and 216.0℃ and average salinity of 24.5%NaCl, much higher than the homogenization temperature and salinity of fluid inclusions in calcite, indicating a high temperature and high salinity diagenetic environment. The isotopic analysis shows that δ¹³C_PDB values vary from-0.01‰ to 3.43‰, and δ¹⁸O_PDB values vary from-11.17‰ to -7.68‰; according to the dolomite-fluid oxygen isotope fractionation equation, the δ¹⁸O_SMOW values of dolomitization fluid are in the range of 4.82‰-12.85‰, It is believed that the matrix dolomite and the saddle dolomite that are filled in the pores in the study area are the products of host limestone altered by the high salinity fluid heated by the magma activity in a close environment, while the high salinity fluid due to the consumption of magnesium ions led to over-saturation of fluid calcite and then to the precipitation if high-temperature calcite. Therefore, hydrothermal activity was very significant for the development of dolomite of the Middle Jurassic Buqu Formation in the study area.

Abstract:In order to investigate source material and sedimentary environment of Lower Paleozoic Wufeng-Longmaxi Formations shale in northwestern Hunan, the authors studied the organic matters, biomarkers and mineral composition. The results show that they have the following characteristics:No odd-even carbon dominance appears; N-alkanes mostly have bimodal performance (C₁₈/C₂₅), and the ratios of ∑C₂₁-/∑C₂₂₊ are 0.45-1.11, indicating the dominant role of heavy hydrocarbon components; the average ratios of Pr/Ph vary from 0.27 to 0.44, showing reduction conditions. The tricyclic terpane values of C₂₁, C₂₃ and C₂₄ show inverted Vshaped distribution, and the ratios of Ts/Tm are between 0.39 and 0.66. The related content of C₂₇ sterane is slightly higher than that of C₂₉ sterane. Based on these features of biomarker, it is believed that the shales of Wufeng-Longmaxi Formation were formed in a reduction environment in shallow water in the Early Paleozoic, with high degree of thermal evolution of organic matter, and the main sources were bacteria, algae and other aquatic organisms. The vitrinite reflectance equivalent values vary from 2.57% to 3.01%, suggesting that all of the shale samples have reached the mature stage. The mineral compositions of the shale samples indicate that quartz and clay minerals dominate the mineral composition, indicating a good brittleness index and adsorption capability. It is concluded that exist favorable geological conditions for shale gas enrichment in the marine shale in the present study area:organic-rich intervals, moderate thermal evolution, good brittleness index and adsorption capability. The results obtained by the authors have laid an important basis for preference of shale gas exploration target area and further gas exploration in this area.

Abstract:Rare metal minerals are important for the development of modern industry and science and technology. The origin and mineralization of pegmatite deposits, which serve as the main sources of rare metal minerals, need to be studied thoroughly. The common disputes include the crystallization differentiation of granites, partial melting of the crust, and magma liquid immiscibility. Studies have shown that lithium isotopes underwent negligible fractionation during crustal anatexis and therefore provide strong evidence for the magmatic source of granites and pegmatites. Mainly from the three aspects of the origin of granite pegmatite, lithium isotope fractionation mechanism, and lithium isotope application in pegmatite deposit, this paper systematically summarizes some research progress made in recent years both in China and abroad. Domestic and foreign geologists have elaborated the Li isotopic composition of the granite pegmatite according to the lithium isotope fractionation mechanism. It is believed that the genesis of the pegmatite deposit may be mainly the crystallization of granite or the partial melting of the crust. However, the study of the origin of in pegmatite deposits is not mature enough and hence more work needs to be done.

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