Abstract:The investigation of natural resources, environmental background and ecological geological conditions is the basis of urban geological survey, which can provide effective basic geological support for urban land spatial planning, construction and delicacy management. With the acceleration of urban development in Xiongan New Area, earth-shaking changes have taken place in its natural resources and ecological environment. Based on the comprehensive geological survey results of Xiongan New Area, the background conditions of natural resources and ecological environment are defined in Xiongan New Area, the variation trend of natural resources is analyzed in the construction cycle, and the natural resources and ecological issues are discussed that should be paid attention to in future urban construction. The results show that the type of land use has been changed dramatically after the establishment of Xiongan New Area. Woods land area increased by about 58.1 km², grass land area increased by about 2.0 km², cultivated land decreased by 68.8km², and construction land increased by 7.2 km². The soil quality is mainly superior and good. The water table of shallow and deep groundwater generally flows from northwest to southeast in Xiongan New Area and gradually decreases, and depression cones of groundwater exit locally. The depth to ground water in shallow aquifers, mainly stabilizing and rising, is generally 5~20 meters. The depth to ground water in deep aquifers is generally 25~35 meters, and the area of water table decline is still relatively high. The wetland of Baiyangdian is rich in animal and plant resources and its water quality is improving gradually. The exploitation and utilization conditions of geothermal resources are good, and the recoverable heat of geothermal fluid is 10.10×10¹⁶J/a, equivalent to 3.4603 million tons/year of standard coal. The ecological environment geological problems should be focused, such as land subsidence and ground cracks, changes of groundwater table, sand liquefaction, potholders and soft soil, etc. existing in the New Area. The effective preventive measures should be taken when necessary to avoid engineering accidents caused by ecological environment geological problems.

Abstract:Coastline transitionally extending from land to sea is the most densely populated area with the most frequent human activities. More than 50% of the global population and 60% of GDP are concentrated in the area less than 100 km away from the coastline. Coastline plays an important indicator role in sea level rise, coastal erosion, estuary siltation, wetland ecological resources, and coastal environment, etc. Remote sensing images were interpreted to acquire data about coastline of Guangdong-Hong Kong-Macao Greater Bay Area(GBA) from 1975 to 2018. Based on GIS platform, the spatio-temporal changes and influencing factors of shoreline were analyzed. The results reveal that the mainland coastline in GBA witnessed significant temporal and spatial changes, which could be divided into two stages. From 1975 to 1995, the length of shoreline increased significantly, the pattern of shoreline type changed significantly; after 1995, the coastline length increased slowly, but the construction land increased strongly. From 1975 to 2018, the coastline of GBA became more and more tortuous, and the fractal dimension increased. In terms of spatial position change, the coastline of the mainland continued to advance toward the sea, with an average rate of 9.91 m/a. The farthest extension to the sea occurred from Hongqimen to Jiaomen and from Hutiaomen to Jitimens with the maximum rate of 197.88 m/a. The development and utilization of the mainland coastline and the intervention of human activities on coastline evolution in GBA increased gradually. The main shorelines affected by human activities were port construction shoreline and reclamation aquaculture shoreline. The natural environment of GBA, such as topography and hydro-logical characteristics was the basis of coastline evolution. Social and economic development and policies were the important driving factors of coastline evolution. At the end of the 20th century, the development speed had the greatest impact on the coastline, and the development intensity was still the main factor at the beginning of the 21st century.

Abstract:Aiming at the problems of ecological environment left behind by abandoned mines, the abandoned gold-mercury mine in Danzhai, Guizhou Province was selected as the research area. Based on the field systematic sampling, the concentrations of mercury (Hg) and arsenic (As) in the soils and crops were analyzed by atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry. The heavy metal pollution level and ecological health risk of soils and crops were evaluated by single factor standard index, single factor index method, potential ecological hazard index and target hazard quotient. The results show that the average concentrations of Hg and As in dryland soil exceed the screening value of heavy metals in agricultural soils, with the exceeding rates of 75.47% and 67.92% respectively. Dryland soil Hg is seriously polluted, showing extremely heavy pollution level, while soil As is mainly medium to extremely heavy pollution. The exceeding rates of Hg and As in aboveground parts of corn (hereinafter referred to as corn) are 36.36% and 4.55% respectively. Corn Hg is slightly polluted, and corn As is not polluted in general. Compared with the dryland-corn system, the Hg over-standard rate and pollution degree of paddy soil are higher, with the exceeding rate of 89.19%, showing an extreme pollution level. However, the over-standard rate of As in paddy soil is only 22.22%, and the As pollution level is lower than that of dryland soil. The average Hg and As concentrations of aboveground rice (hereinafter referred to as rice) are slightly higher than the food safety standards, and the exceeding rates are 54.55% and 18.18% respectively. The Hg and As pollution levels of rice keep higher than those of corn, and the pollution levels is in the light to medium range. The potential ecological hazard index shows that Hg ecological risk in soils is mainly extremely strong, and As ecological risk is mainly slight. It is difficult for Hg to migrate to crop seeds, so there is no obvious non-carcinogenic risks by eating corn and rice. However, the accumulation of As in rice can result in significant non-carcinogenic and carcinogenic health risks. This study is of great significance to ensure the health of mining residents, and the results can provide scientific basis for the ecological environment impact assessment and ecological restoration in mining areas.

Abstract:Large number of geothermal fields are distributed on the margin and inside of the Tibetan Plateau, such as Gonghe-Guide geothermal field, Zhangye geothermal field, Tianshui geothermal field and Tengchong geothermal field. All these geothermal fields are basically characterized by zonal distribution along the Tibetan Plateau and systematically controlled by its tectonic activities. The analysis on multiple geothermal fields shows that they all have a deep heat source with vertical upward heating conduction through favorable channels from deep faults to their secondary faults. It is revealed that several channel flows exist under the deep Tibetan Plateau and are remarkably shown in geophysical data like the seismic tomographic imaging and teleseismic P-wave travel time tomography. It has also been verified by petrologic evidence that the low-velocity and high conductive layer beneath the crust of the Mid-Northern Tibetan Plateau is a partial melting layer. In view of geothermal fields distributed along the channel flow and combined with other research results, it is believed that the channel flows not only act as heating resources, but also form significant abnormal zones of terrestrial heat flow. In the area of channel flows, crust is thinned, structural activities are intensified, which enables heat to be easily transferred upward. According to comprehensive analysis, the relationship model of geothermal distribution and channel flow, and the geothermal field model related to channel flow are preliminarily established. It is believed that geothermal fields distributed in the northeast margin of the Tibetan Plateau are controlled by the channel flow in the deep crust. Through the analysis of the prospect of geothermal resources in this area, it is suggested that the Tianshui area in Gansu Province is located at the intersection of channel flows, and has great potential for prospecting of geothermal resources.

Abstract:P Porphyry tungsten deposit is the third most important type in the world, but its research is weak and scattered. This paper systematically summarizes and analyzes the research results in recent years from our team and other scholars about porphyry tungsten deposits. The results show that porphyry tungsten deposits are widely distributed in the Circum-Pacific metallogenic belt and the Alps-Himalayan metallogenic belt, and occur in magmatic arc, intraplate, and continental collision settings. Most of them were formed in Mesozoic and a few in Paleozoic. Porphyry tungsten mineralization is closely related to weakly oxidized, highly fractionated I-type or A-type hypabyssal granitic rocks, which were mainly derived from re-melting of the ancient crust, contaminated with a small amount of juvenile crust and/or depleted mantle and/or marine sediments. The ore-forming metals and fluids were dominantly originated from related magmatic rocks, and the Ca²⁺, Fe²⁺, and Mn²⁺ needed for W mineralization could be provided by the strata and magmatic rocks through water-rock reaction. The initial ore-forming fluids of porphyry tungsten deposits in magma arc and intraplate settings belong to the NaCl-H₂O system with medium-high temperature, medium-high salinity and low CO₂ content, while those under continental collision setting belong to NaCl-H₂O-CO₂ system with medium-high temperature, medium-low salinity and high CO₂ content. W tends to be enriched in the coexisting fluid phase in the process of melt-fluid differentiation, and then migrates in the form of monomer tungstate, polytungstate, and fluorotungstate. The mechanisms of mineral precipitation mainly include fluid immiscibility/boiling/CO₂ escape ±fluid mixing and water- rock reaction. Scheelite and wolframite are the dominant W-bearing minerals in porphyry tungsten deposits, and their occurrence may be mainly controlled by the fluorine content in relevant magma-fluid system.

Abstract:In order to understand the impact of the early extensive mining activities in the Tongguan gold mine on the heavy metal pollution of the farmland soil and the evaluation of the adverse health effects of the exposed population, enginnering six farmland soils near the mine area were selected as the research object in the geological survey. Spectral analysis method was used to determine the contents of Cd, Hg, As, Pb, Cr, Cu, Ni, Zn and other 8 soil heavy metals of 68 soil samples. The soil accumulation index method, potential ecological hazard index method and health risk assessment model were used to evaluate the soil heavy metal pollution degree, potential ecological risk and human health risk in the area. The results show that the average values of Ni, Hg, Cd, Zn, Pb and Cu in the farmland soil in this area are higher than the soil background value of Tongguan County, indicating different levels of accumulation. The accumulated soil content of Pb, Hg, and Cd not only exceeds the minimum limit of the safety risk of heavy metal pollution, bu also exceeds the maximum limit of the safety risk of heavy metal pollution on the quality of agricultural products by 41.2%, 72.1%, and 14.7% of the exceedance rates respectively. The evaluation of soil heavy metal pollution in the study area shows that the total pollution degree of Hg, Cd and Pb in the soil is the heaviest, Cu and Zn are generally light to heavy pollution, and Ni, Cr and As are generally pollution-free. The ecological risk assessment shows that Hg, Cd, and Pb are the main ecological hazard elements, Hg is a very strong risk, and Cd and Pb are strong risks. Human health risks show that the non-carcinogenic risk of heavy metals to children is obvious, and Pb and Hg are the main non-carcinogenic factors. Carcinogenic risks are within a reasonable range. Cd is the most carcinogenic risk, and hand-mouth intake is the most important exposure route. Children are more vulnerable to heavy metal pollution.

Abstract:Selenium has an important impact on human health. This paper takes Gaocheng as a research object to test and analyze the content of selenium and heavy metal elements in different media in the study area with HG-AFS and ICP-MS method. Based on the discussing of the characteristics, main causes and sources of selenium content in soil, the health of the local ecological environment is evaluated. The results show that the average selenium in the surface soil of Gaocheng is 0.32mg/kg, and the enrichment coefficient reaches 1.68, which is generally higher in the southern part of the study area, about 171.12 km² reaching the standard of selenium-rich soil. The selenium enrichment in soil is mainly caused by human beings, and its main sources are coal burning and irrigation water. The selenium content of agricultural products in the selenium-rich area is much higher than that in the non-selenium-rich area, part of which meets the natural selenium-rich food standard. The selenium intake of residents is about 123.47 mg/d, which is at a reasonable level. The heavy metal pollution degree is Cd> Hg> Pb> Cu> Zn> Ni> As. The ecological risk assessmen of a single heavy metal t shows that Cd and Hg are the main hazard elements, and the other heavy metal potential risks are low. The human health risk assessment of heavy metals indicates that the non-carcinogenic and carcinogenic risk indexes in the study area are within a safe range, and oral intake is a source of health. Children are more vulnerable to oral intake than adults.

Abstract:Inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) were used to quantitatively analyze rare earth elements of the No. 15 Coal in Changzhi Shouyang Mine, Qinshui Coalfield for discussing its enrichment mechanism, distribution pattern, occurrence state and coal-forming environment. The results show that the average content of rare earth elements in the coal seam of the study area is 49.28 μg/g, and the overall content is relatively low. Except for SYS15-2, the rare earth elements of No.15 coal seam and gangue are all enriched in light rare earth (LREY), and the accumulation of light rare earth in gangue is more obvious. Rare earth elements occur mainly in clay minerals. On the whole, the coal-forming environment is dominated by weak reduction environment, and the source of rare earth elements is mainly terrigenous debris.

Abstract:The buried depth of the coal seams of South Yanchuan block is between 700 m and 1500 m. And for the most area, the depth is deeper than 900 m. In order to clarify the in-situ stress state of deep coal-bed methane reservoir and its influence on the development of CBM wells, the maximum and minimum horizontal principal stress and the vertical stress are calculated based on the pressure drop data of hydraulic fracturing. The results show that the whole area is in the state of tension. The maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress are positively correlated with the buried depth. The type of the ground stress is mainly type Ia, followed by III type and II type. The reservoir with type Ia ground stress is dominated by vertical fractures with the lowest fracture index. However, the stress sensitivity is weak, and the stress sensitivity coefficient is only 0.479. The main and secondary fractures of type I stress reservoir are 16μm and 11μm respectively, with the largest width and the strongest reservoir stress sensitivity. Type I fractures are mainly horizontal fractures, with the highest fracture index, the longest compression fracture, the best reconstruction effect and the highest gas production. Reservoirs with type III in-situ stress develop complex fractures, with medium permeability,stress sensitivity and hydraulic fracture length. However, the production for type III is relatively low, and cannot achieve economic development.

Abstract:Carbonate rocks in China tend to have the characteristics of the older development period, deeper burial, and stronger later diagenetic transformation, which leaves a large space for the study of high-quality carbonate reservoirs and their main controlling factors in China. During the sedimentary period of Majiagou Formation in the Ordos Basin, the basin witnessed changing from tension to longitudinal compression, which induced a series of tectonic activities. To explore the influence of different tectonic activities on the subsalt deposition of Mawu Member in Majiagou Age, based on the previous studies and under the guidance of carbonate sedimentology, two-dimensional seismic profiles in the study area were analyzed, and differential tectonic activities were summarized. Combined with the analysis of seismic facies and sedimentary facies in the sub-salt sedimentary period of the Mawu Member, the influence of differential tectonic activities on the grain beach reservoir were depicted. As a result, the following understandings are obtained:a. four types of seismic facies have been identified in the study area, corresponding to different types of sedimentary facies, of which the grain beach facies is a good reservoir in the study area; b. there are three types of tectonic activities in the basin, basement faults (sag troughs), synsedimentary faults and uplifts;and c. based on the matching analysis of different types of tectonic activities and grain beach reservoirs, the control of differential structural activities on the development and distribution of this kind of carbonate reservoir is finally obtained, and its action mode is summarized. Finally, granular beach reservoirs are divided into fault-controlled reservoirs and uplift-controlled reservoirs.

Abstract:The oil-gas reservoir flow units have been widely used in the characterization of high, medium and low permeability reservoirs, but they are still rarely involved in the study of ultra-low permeability reservoirs. As to a case of the ultra-low permeability reservoirs of the Fuyu oil layers in the Fourth Member of the Lower Cretaceous Quantou Formation in Sheng 554 fault block of Sanzhao Sag in northern Songliao Basin, three types of flow units have been classified, including E type, G type and P type. The flow capacity is gradually reduced from E type to P type. The physical and spatial distribution characteristics of the flow units indicate that the flow units reservoirs are highly heterogeneous. The controlling effects of sedimentary facies and open normal faults on the development of flow units are analyzed. It is found that the flow capacity of the flow units themselves has little effect on the reservoir development, and the difference of the reservoir development effect caused by the difference of the flow capacity among different flow units is not obvious in the scale of ultra-low permeability reservoirs. The development effect mainly depends on the development factors such as the thickness of the perforated sandbody and the effect of water injection, and the geological factors such as the fault seepage channel, the mudstone seepage barrier and the thickness of sandbody. This is quite different from the previous view that the more the flow capacity of flow units is, the better the reservoir development effect of water injection is. The result is expected to provide some reference for the study of flow units in ultra-low permeability oil-gas reservoirs and for the development of ultra-low permeability reservoirs.

Abstract:Taking the South Xihu depression as a study case, the authors applies the research idea of distributive fluvial system (DFS) to the study of the sedimentary system of the East China Sea Basin. By summarizing the forming conditions of large DFS, it is concluded that the south Xihu depression is near the source and under stable tectonic condition, and there also exists large basin and mountain systems, which is favorable for forming large DFS. Based on the characteristics of the core and paleontology of Huagang Formation, the author divided branch channels into some types, and indicated that the main types of FS are braided bifurcating and single braided channels. Different types of channels have the potential for developing thick sand bodies. Combined with the features of the paleotopography and sedimentary system distribution, the study of the patterns of DFS distribution shows that the study area has developed two sets of DFS, which are distributed respectively from western slope to the northeast and southeast. The DFS end belongs to "the axial end" type, suggesting that the axial limited rivers of Xihu depression and DFS has formed a convergence zone with reservoir exploration potential.

Abstract:The Mohe Formation is widely developed in Mohe Basin which is located in the northern part of the Da Hinggan Mountains. Its formation age, provenance characteristics and tectonic background are of great geological significance for the study of the formation and evolution of the basin. Two interbeds of tuff were discovered in the Mohe Formation in the western margin of Mohe basin, Enhe-Hada area. Zircon U-Pb dating by LA-ICP-MS U-Pb method yields the weighted average ages of (158±1) Ma and (157±2) Ma respectively, indicating that the Mohe Formation rocks were formed in early Late Jurassic. The geochemical analysis of Mohe Formation sandstone shows that the content of SiO₂ is high (70.20%-76.13%), the value of SiO₂/Al₂O₃ is 4.99-5.87, and the value of K₂O/Na₂O is 0.59-1.62. In the chondrite-standardized diagram of rare earth elements, the curve is consistent with that of the active continental margin. In the high field strong elements and large-ion lithophile elements, the samples are enriched in Th, Hf, Rb and K, and deficit in Nb,Ta, Ti, P, Ba and Sr. The cobweb curve of trace elements is similar to that of the active continental margin. The geochemical source analysis and tectonic background discrimination show that the parent rocks of the Mohe Formation sandstone were mainly originated from the mixing of the quartzite sedimentary rocks and the acidic volcanic rocks. The ages of the detrital zircons in the sandstone coincide with the ages of the Precambrian basement and granitic rocks in the southern margin of the basin. The formation age, provenance characteristics and tectonic setting of the Mohe Formation, which is widely developed in the Mohe Basin in the north of the Great Hinggan Mountains, are of great significance to the study of the formation and evolution of the basin.

Abstract:Luodian, located in the southern Guizhou Province, belongs to the outer zone of Emeishan Large Igneous Province. Numerous diabase of the same period as the Emeishan Large Igneous Province are exposed in the area. The acidic dykes are quartz monzonite porphyry, and invade into diabase. The study of acidic dykes is conducive to enriching the understanding of the law of lithology combination and magmatism in Emeishan Large Igneous Province. Petrology, SIMS chronological and geochemical studies of the acidic rock in Luodian were performed. Average content of major oxides are SiO₂ 66.83%, Cao 1.76%, Al₂O₃ 14.74%, MgO 0.76%, TFe₂O₃ 4.49%, K₂O 3.67%, Na₂O 5.24%, and average value of A/CNK is 0.93, displaying the features of high silicon, rich alkali and quasi-aluminous. (La/Yb)_N ratios of 7.71 to 10.60 displays apparent differentiation between LREE and HREE with an average δEu of 0.91. The chondrite-normalized curve of REE is right inclined, showing ocean island basalts (OIB) signature. The dykes are enriched in elements such as Rb, Ba, Th, K and Nd, and depleted in elements such as Nb, Ta, P and Ti. The values of (⁸⁷Sr/⁸⁶Sr)_i (0.704247-0.705292) and ε_Nd(t)(1.08-1.54) are similar to those of diabase. It is suggested that the acidic rock is originated from fractional crystallization of basaltic magma produced by partial melting of mantle plume, and contaminated with a small amount of upper crust material. The acidic rock was dated at (259±2) Ma by SIMS, which is consistent with the magmatism age of the Emeishan Large Igneous Province. The large number of inherited zircons in the samples were found, might be the response to tectonic activity at different stages in the Yangtze block.

Abstract:Wood grown rings, named as wood-like stone, are developed in carbonatites in Hohhot, Inner Mongolia. The wood-like stone, looking like wood grown rings, is very fine grained, smooth surface with red and pale yellow ring surroundings. Based on field investigation, the mineralogy and petro-geochemistry of the wood-like stone were studied for colorful rings, and the distribution of elements was tested by SEM. The results indicate that the wood-like stone consists of mediate to fine grained dolomite with argillaceous cement. The cement is mainly composed of sericite, K-feldspar, clay minerals and a few ilmenite, pyrite, limonite and REE minerals. Chemically, Al₂O₃, K₂O and Fe₂O₃ are richer in red ring than that in pale yellow one. Especially for the Fe element, the cps of Fe about 350 in the line scan can be used as the standard to distinguish the stripes of different colors. According to the graphical analysis of Yb/(Ca+Mg)-Yb/La, the rocks show signs of hot water activity. It is indicated that the marine carbonatite was infiltrated by hot fluids flowing through fractures after deposition. Due to the difference of temperature, Fe oxidation difference and the different content of trivalent Fe resulted in red-yellow stripe, forming the ring belt with cracks as the boundary like the tree ornamentation.

Abstract:The Yuangezhuang Pluton located in the east of Jiaodong area, is formed in the late Yanshanian and is one of the granites associated with Cu-Mo polymetallic deposits hosted inporphyry and skarn. LA-ICP-MS zircon U-Pb dating of Yaxi unite, Houye unite and Xishangzhai unite from the Yuangezhuang monzonitic granite yields (118.10±0.66) Ma, (118.52±0.78) Ma,and (118.80±0.67) Ma respectively, indicating the Late Epoch of Early Cretaceous. The results of petrochemistry indicate the pluton is belong to high-K calc-alkaline serie (K₂O/Na₂O=1.00-1.29, A/CNK=0.98-1.02). The results of trace elements are characterized by dramatic fractionation between light REE and heavy (REE(La/Yb)_N=26.91~35.75 unapparent Eu anomalies (δEu=0.84-0.93), enriched in LILE (i.e. Rb,K,U) and loss in HSFE (i.e. Nb,Ti,P). The geochemical characteristics indicate the Yuangezhuang pluton is an I type granite, crust-mantle syntectic granite. The pluton has strong constrain on spatial distribution and metallogenic epoch of Cu-Mo deposits.

Abstract:The shape and dominant spatial orientation of soil particles are the important cause of macroscopic soil anisotropy. Based on Quanta FEG scanning electron micrograph, the late Pleistocene Malan loess with obvious anisotropy was studied to reveal the difference of the microstructure in the horizontal and vertical directions and the anisotropic cause of the microstructure. The results show that the roundness R₀ of the particles in the horizontal and vertical slices has normal distribution characteristics. Subcircular, circular and very circular particles are the main types of soil particles in both vertical and horizontal directions. The azimuth of the particles in the horizontal slice has a certain dominant direction of WN-ES, while the long axis of the soil particles in the vertical slice has the dominant orientation parallel to the ground, and the deeper the buried depth is, the more obvious the trend is. The isotropic nature of the soil particles in the horizontal section is more significant, while the anisotropic properties of the particles in the vertical section are more prominent, and the anisotropy increases with the buried depth. The total probability distribution of particles in horizontal and vertical slices is basically disordered. The quantitative advantage of the particles is a major reason for this disordered distribution. Compared with the fine particles, fine sand, to some extent, has the preference of a certain orientation in alignment. The analysis shows that the azimuth and anisotropy of the particles have a good indication to microscopic anisotropy of the loess. At the same time, the direction of particles also is of significance for the study of paleoclimate of the Loess Plateau.

Abstract:Many K-bentonites have been recognized from the Wufeng-Longmaxi Formations (Upper Ordovician-Lower Silurian) in the Yangtze Block, but only a few of them on the western margin of the Yangtze Block are reported. The mineralogical and geochemical studies of K-bentonites in the Wufeng-Longmaxi Formations through Xindi 2 well in Daguan area of Yunnan province were carried out to confirm the original magma type and its tectonic setting. The mineralogical characteristics show that the potassium bentonite is mainly composed of clay minerals and non-clay minerals, in which the clay minerals are composed of illite and illite-montmorillonite mixed beds. The non-clay minerals are mainly quartz, feldspar, calcite, dolomite and pyrite. It is geochemically characterized by high K₂O and low TiO₂, relative enrichment of Rb, Ba, Th and U and depletion of Ti and P elements. The Ti/Th values indicates acidic volcanic ash character. Compared with the chondrite, the total rare earth elements is (49.86-209.43)×10^-6 with slight rich LREE and negative Eu amomaly, without Ce abnormity. In Nb/Y-Zr/TiO₂ diagram, the data dots are mainly plotted in the andesite and trachy andesite range, which shows that the volcanic ash is mostly from middle-acid rocks. Various chemical discrimination diagrams and trace elements imply that K-bentonites were possibly derived from an island arc environment,and the volcanic ash was probably related to the subduction and closure of the Qinling Ocean on the northern border of Yangtze Plate in the Early Paleozoic.

Abstract:The Devonian System in Daguan County of Yunnan Province is rich in quartz sand resources. The study of stratigraphic sequence in this area can not only contribute to the in-depth analysis of the paleogeographic environment and its variation characteristics of quartz sand formation, but also can reveal the formation and distribution rules of quartz sand with the help of tectonic background, and finally provide theoretical basis for the development of silicon industry. Therefore, based on the field stratigraphic profiling and core logging of shale gas wells, and combined with the paleotectonic background, this paper studied the Devonian profile characteristics in Daguan and Yanjin counties in northeast Yunnan Province with a straight-line distance of less than 50 kilometers. This area is located in the northern margin of Dianqiangui rift in Late Paleozonic, where controlled by the edge facies zone, two sets of high maturity quartz sandstone were deposited in Posongchong Formation and Suotoushan Formation. In general, seven Devonian formations were deposited, including Posongchong, Pojiao, Qingmen, Suotoushan, Hongyapo, Qujing, Zaijieshan from bottom to top in order, but these seven formations are often incomplete and vary very frequently at different locations. Controlled by the pattern of uplift and depression in the rift basin and syngenetic fractures, the sedimentary sequence is often inconsistent in different locations. The Devonian strata witnessed two regressive and transgressive depositional processes, reflecting the formation process from continental shelf construction to carbonate platform, and the strata of each formation are similar to those of stratotype section with certain variety characteristics. On the whole, the resource potential of Suotoushan Formation is better than that of Posongchong Formation. Zhonghe Town of Yanjin County is the most promising development prospect of industrial quartz sand for the Posongchong Formation, and Mugan Town and Huangjingba Town of Daguan County are the most promising prospects for the Suotoushan Formation, which are of guiding significance to the exploration of Devonian quartz sand.

Abstract:Shallow geothermal energy has attracted extensive attention at home and abroad as a new type renewable energy. Resistance temperature sensors, as susceptible to electromagnetic interference, are not suitable for long-term use. The distribution-based fiber optic temperature measurement technology with strong anti-interference ability was used in 19 boreholes to a depth of 100 meters in Nanjing City. In the winter of 2018 and spring of 2019, the distribution of shallow uground temperature in Nanjing was obtained from the 19 boreholes. Based on the hydrological and geological conditions in Nanjing, it is concluded that the change of shallow ground temperature is lagged relative to the change of air temperature. For the shallow ground temperature in the same location, the flow of groundwater will lead to different ground temperature in different seasons. Structural conditions significantly affect the distribution of shallow ground temperature. The results can provide a reference for the utilization and further development of shallow geothermal energy in Nanjing.

Abstract:As an important part of shale reservoir space, organic pores possess strong heterogeneity, which hinders the correct understanding and evaluation of shale reservoir quality. The heterogeneity is essentially affected by organic macerals and their pore evolution during hydrocarbon generation process. Through located observation based on the field emission scanning electron microscopy and optical microscopy for pore development of the specific macerals, combined with Image J digital process technique, the pore evolution law of different organic macerals was summarized by quantitative statistics of macerals at different evolutionary stages. The results show that the porosity with solid bitumen is first increased and then decreased with the increase of maturity. The solid bitumen porosity is the highest when SBR_O rangs from 1.6% to 2.0%, while the porosity begins to decrease when SBR_O exceeds 2.0%. The pore development models of vitrinite and inertinite are similar. The both porosity decreases first and then increases slightly as maturity rise. In the oil window stage, the porosity of vitrinite and and inertinite is the lowest, because the filling of inorganic minerals and solid bitumen in the primary cell lumen make the loss of pores more than 90%. In the high mature stage, pore development of solid bitumen makes the original cellular pore getting a certain degree of recovery, becoming the main contribution and accounting for 56.73% and 100% of residual pores of vitrinite and inertinite respectively. It can be seen that solid bitumen pores are of importantance to the shale reservoir. Combined with sedimentary diagenesis and hydrocarbon generation, the pores of shale reservoir are the most developed in the immature stage and the late stage of high maturity. The former is dominated by primitive cell pores, while the latter is dominated by solid bitumen pores. Clarification of the pore evolution pattern of organic macerals can provide a significant reference for favorable shale reservoir prediction and reconstruction of shale gas development.

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