Based on the latest geological,seismic,drilling and outcrop data,we studied the geological structure,tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the pote...Based on the latest geological,seismic,drilling and outcrop data,we studied the geological structure,tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the potential hydrocarbon exploration areas in deep layers.During key tectonic periods,the southwestern Sichuan fold-thrust belt developed some characteristic strata and structural deformation features,including the Pre-Sinian multi-row N-S strike rifts,step-shaped platform-margin structures of Sinian Dengying Formation,the western paleo-uplift in the early stage of Late Paleozoic,the Late Paleozoic–Middle Triassic carbonate platform,foreland slope and forebulge during Late Triassic to Cretaceous,and Cenozoic multi-strike rejuvenated fold-thrusting structures.The fold-thrust belt vertically shows a double-layer structural deformation controlled by the salt layer in the Middle Triassic Leikoupo Formation and the base detachment layer at present.The upper deformation layer develops the NE-SW strike thrusts propagating toward basin in long distance,while the deeper deformation layer had near north-south strike basement-involved folds,which deformed the detachment and thrusting structures formed earlier in the upper layer,with the deformation strength high in south part and weak in north part.The southern part of the fold-thrust belt is characterized by basement-involved fold-thrusts formed late,while the central-northern part is dominated by thin-skin thrusts in the shallow layer.The Wuzhongshan anticlinal belt near piedmont is characterized by over-thrust structure above the salt detachment,where the upper over-thrusting nappe consists of a complicated fold core and front limb of a fault-bend fold,while the deep layer has stable subtle in-situ structures.Favorable exploration strata and areas have been identified both in the upper and deeper deformation layers separated by regional salt detachment,wherein multiple anticlinal structures are targets for exploration.Other potential exploration strata and areas in southwestern Sichuan fold-thrust belt include the deep Sinian and Permian in the Wuzhongshan structure,pre-Sinian rifting sequences and related structures,platform-margin belt of Sinian Dengying Formation,and Indosinian paleo-uplift in the east of the Longquanshan structure.展开更多
The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling ...The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.展开更多
The investigation of the in situ stress distribution has always been a key condition for engineering design of deep tunnels and analysis of surrounding rock stability.In this paper,a comprehensive judgment method coup...The investigation of the in situ stress distribution has always been a key condition for engineering design of deep tunnels and analysis of surrounding rock stability.In this paper,a comprehensive judgment method coupled with pressure/tension(P/T)axis mechanism and geological structure is proposed to invert the in situ stress in the Duoxiongla tunnel in Tibet.In the process of TBM tunnel excavation,3887 groups of microseismic events were collected by means of microseismic monitoring technology.By studying the temporal and spatial distribution of 3887 groups of microseismic events,42 groups of microseismic data were selected for in situ stress inversion.Then the focal mechanisms of 42 groups of microseisms were inverted.Combined with the analysis of the previous geological survey,the inversion results of the in situ stress were analyzed.According to the focal mechanism of the tunnel area,the linear in situ stress inversion method was used to invert the in situ stress in the source area.Finally,according to the PTGS(pressure/tension axis mechanism and geological structure)comprehensive judgment method proposed in this paper,the in situ stress of the tunnel microseismic region was determined.The results show that there are mainly three groups of fissures and joint surfaces in the tunnel area,and the in situ stress is dominated by the horizontrun tectonic stress;the main driving force of the rupture surface in the excavation process of Duoxiongla tunnel is the horizontal tectonic stress;the distribution of the maximum and minimum principal stress obtained by the inversion is consistent with the distribution of the P/T axis;combined with the linear in situ stress inversion method and the comprehensive judgment of PTGS,the azimuth and dip angles of the three principal stresses are finally determined as N90.71°E,4.06°,N5.35°W,3.06°,and N8.10W,85.32°,respectively.The study verifies the feasibility of microseismic inversion of in situ stress.展开更多
Uncertainty in 3D geological structure models has become a bottleneck that restricts the development and application of 3D geological modeling.In order to solve this problem during periods of accuracy assessment,error...Uncertainty in 3D geological structure models has become a bottleneck that restricts the development and application of 3D geological modeling.In order to solve this problem during periods of accuracy assessment,error detection and dynamic correction in 3D geological structure models,we have reviewed the current situation and development trends in 3D geological modeling.The main context of uncertainty in 3D geological structure models is discussed.Major research issues and a general framework system of uncertainty in 3D geological structure models are proposed.We have described in detail the integration of development practices of 3D geological modeling systems,as well as the implementation process for uncertainty evaluation in 3D geological structure models.This study has laid the basis to build theoretical and methodological systems for accuracy assessment and error correction in 3D geological models and can assist in improving 3D modeling techniques under complex geological conditions.展开更多
Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the d...Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin.(1)The geological structure of the Termit Basin is represented as a narrow rift basin,with development of series of structural styles in extensional,extensional strike-slip and compressional stress setting.On plane,it is narrow in the north and wide in the south,and transitions from graben to half-graben from north to south;it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south.(2)Before the Cretaceous,a series of hidden faults developed in the West African rift system,which laid the foundation for the development location and distribution direction of the Termit Basin;during the Cretaceous to Paleogene periods,the basin experienced two phases of rifting in Early Cretaceous and Paleogene,which controlled the initial structure and current structural shape of the basin respectively;during the Neogene to Quaternary,the basin was subjected to weak transformation.(3)In the Precambrian,the Pan-African movement gave rise to a narrow and long weak zone within the African plate,which provided the pre-existing structural conditions for the formation of the Termit Basin.In the Early Cretaceous,affected by the South Atlantic rifting,the Pan African weak zone was reactivated,resulting in the first stage of rifting and the basic structural framework of the Termit Basin.In the Paleogene,affected by the subduction and convergence of the Neo-Tethys Ocean,the African-Arabian plate extended in near E-W trending,and the Termit Basin experienced the second stage of rifting.The oblique extension in this period caused intense structural differentiation,and the current structural pattern of alternate uplifts and depressions took shape gradually.展开更多
The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geologica...The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geological data. The main results are summarized as follows: ( The geotectonic subdivisions and the characteristics of main deep and large faults in the northeastern margin of the Qinghai-Tibetan plateau are presented; ( The general features of the Moho are obtained mainly based on artificial seismic sounding data; ( There exists well corresponding relation between surface faults and some features of the Moho, which suggests that such complex crustal structure might be the preparation environment of strong earthquakes.展开更多
As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoy...As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoyuzhuang,Yangzhuang,Wumishan,Hongshuizhuang,and Tieling formations.The characteristics,formation periods,and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops,cores,thin sections,and image logs.The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40°to 70°and the fracture porosity increases linearly with an increased fracture aperture.Within the same tectonic setting and stress field,the lithology and layer thickness are the dominant factors governing the development of tectonic fractures,which are the most developed in dolomites and thin layers.Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients.The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets:NNW-SSE and NNE-SSW oriented‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement;NE-SW-oriented shear fractures,formed in episode B of the Yanshanian Movement,occurred at the Early Cretaceous;nearly E-W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene,and NEE-SW-oriented shear fractures formed during the Himalayan movement.展开更多
The spatial prediction of geothermal sites along the southeast side of Taihang Mountain in the Tangyin rift is a critical goal in the development of renewable energy resources in cities such as Hebi in Henan province,...The spatial prediction of geothermal sites along the southeast side of Taihang Mountain in the Tangyin rift is a critical goal in the development of renewable energy resources in cities such as Hebi in Henan province,which has significant potential for geothermal energy production due to the existence of deep faults and Cenozoic volcano.The study aimed to delineate areas with high geothermal manifestations for detailed geothermal exploration and well-test drilling.To define favorable zones for geothermal potentiality,multi-source datasets were chosen to generate evidence thematic layers that demonstrate the distribution of geothermal anomalies such as geologic maps,structural maps,Land Surface Temperature maps(LST),and hydrothermal mineral alterations maps.The remote sensing and Geographical Information System(GIS)approaches were integrated to map fossil geothermal manifestations and appraise the promising geothermal zones from Landsat 8 OLI/TIRS and Advanced Spaceborne Thermal Emission and Reflection Radiometer-Digital Elevation Model(ASTER-DEM)dataset using the Analytic Hierarchy Process(AHP),which is one of the Mult-criteria Decision Making methods.Results show LST values ranging from 22.6℃ to 45.4℃,with the highest values found along the faults and volcanic areas.The hydrothermal alteration minerals discriminated from band ratios of 4/2,6/5,and 6/7 for iron oxide,ferrous minerals,and clays reveal the presence of high amount of montmorillonite and illite minerals along the faults and volcanoes which are related to hot fluid circulation from subsurface.Structural analysis shows that the major structural trend follows the NNE Tangdong and Tangxi faults,with high density on the west side of the Tangxi fault where there is good exposure of outcrop but less fault density on the east side due to sedimentation in a low land which may conceal geological structures.Lastly,all the thematic layers of geothermal factors were reclassified,ranked,and integrated by the weight overlay logic model based on the influence of geothermal suitability to map potential areas for geothermal resources whereby 5 zones were obtained ranging from very poor to very good.The promising potential sites are mostly found along the highly deep structures of the major Tangxi fault crosscutting the permeable lithology of carbonate rocks and around the Hebi volcanoes.The distribution of hot springs and geothermal wells of the Hebi field were correlated and verified against the potential geothermal anomalies map.The overall integrated method proposes an advanced technique for designing the Tangyin rift’s exploration plan and development actions for geothermal resources utilization,which can be used for exploration of any unveiling geothermal potential sites.展开更多
Utilization of urban underground space has become a vital approach to alleviate the strain on urban land resources,and to optimize the structure and pattem of the city.It is also very important to improve the city env...Utilization of urban underground space has become a vital approach to alleviate the strain on urban land resources,and to optimize the structure and pattem of the city.It is also very important to improve the city environment,build livable city and increase the capacity of the city.Based on the analysis of existing evaluation methods and their problems,a method for evaluating underground space resources based on a negative list of adverse factors affecting underground space development is proposed,to be primarily used in urban planning stages.A list of the adverse factors is established,including limiting factors,constraining factors and influencing factors.Taking Xi'an as an example,using a geographical information system platform,a negative list of adverse factors for the underground space resources in Xi'an City are evaluated,and preventive measures are proposed.Natural resources,exploitable resources,and the potential growth of exploitable underground space resources are evaluated.Underground space assessment in the different development stages of the city,collaborative utilization and safety evaluation for multiple subsurface resources,environmental impact and assessment,as well as evaluation methods based on big data and intelligent optimization algorithms are all discussed with the aim of serving city planning and construction.展开更多
The Baiyun cave is a 380 m long karst cave in the Naigu Shilin, situated 70 km southeast of Kunming,Yunnan Province, China. The prevailing orientations of the cave passages are N110°-120°E and N0°-10...The Baiyun cave is a 380 m long karst cave in the Naigu Shilin, situated 70 km southeast of Kunming,Yunnan Province, China. The prevailing orientations of the cave passages are N110°-120°E and N0°-10°W and those of the fissures in the cave are N30°-40°W and N20°-30°W. The cave is developed in the thick-bedded Lower Permian Qixia Formation. The cave has an active water flow and is currently at the near water-table stage. There are large amounts of different infills of cave sediments. The cave shows different stages of paragenesis. The palaeomagnetic analysis of cave sediments shows that their ages are younger than 780 ka B.P. (the Brunhes Chron). The upper part of the sampled profile belongs to the reverse Blake event (112.3-117.9 ka B.P.). The formation of the Baiyun cave is directly connected with the development of the Naigu Shilin. The formation of karst underground and surface features depends on the regional tectonic deformation and the Cenozoic extension of the study area.展开更多
The thermal effect caused by deep magma intrusion can not only accelerate the metamorphism of coal body,but also bring additional thermal field that changes the mechanical environment of coal seams,thereby affecting t...The thermal effect caused by deep magma intrusion can not only accelerate the metamorphism of coal body,but also bring additional thermal field that changes the mechanical environment of coal seams,thereby affecting the permeability of coal seams.Different from shallow coal resources,deep coal resources are in a mechanical environment characterized by limited stress and strain.Thus,the thermal effect has a more significant influence on the distribution and permeability characteristics of deep coal seams.In this study,the evolution history of highly metamorphic coal seams in Yangquan mining area was analyzed,and the main effect of magmatic activity on coal seams was obtained.Based on the determined vitrinite reflectance data of typical mines in Yangquan mining area,the maximum paleotemperature was calculated by adopting the Barker’s method.Furthermore,the paleotemperature distribution in Yangquan mining area was summarized,and its relationship with the metamorphic degree was acquired.Then,a new permeability model considering the thermal strain was proposed to analyze the permeability evolution in deep coal seams at different ground temperatures.Finally,through a combination of the results of gas pressure and outburst number in Sijiazhuang Mine,Yangquan No.5 Mine and Xinjing Mine,the influence of ground temperature on the gas outburst risk in Yangquan mining area was explored.The following conclusions were drawn:The maximum paleotemperature in Yangquan area can be 303C.In addition,the paleotemperature in the south is higher than that in the north of Yangquan mining area.The various temperatures at different depths bring about different degrees of thermal stress to different coal seams,leading to different strains.Under the fixed displacement boundary conditions in the deep,the coal seam folds and bends to varying degrees.Moreover,the difference in the ground temperature raises the a value of coal seams and lowers the permeability,which promotes the formation of gas-rich zones and increases the risk of coal seam outburst.The research results can help mines to make proper gas disaster prevention plan for different zones.展开更多
Geothermal resources exist in complex and comprehensive geological settings. In the current study, we proposed a CPU/GPU collaborative parallel prestack time migration methodology for geothermal resource exploration. ...Geothermal resources exist in complex and comprehensive geological settings. In the current study, we proposed a CPU/GPU collaborative parallel prestack time migration methodology for geothermal resource exploration. First, seismic geological conditions in Xian County were obtained based on an analysis of drill cores for further seismic evaluation. Then,combined with the analysis of two-dimensional seismic data in the adjacent area, a test section with three seismic survey lines were designed to explore the geological structure of the study area. In the study area, the seismic data were derived through the multiple coverage reflection wave exploration method with explosive ignition in deep wells and high coverage frequency observations. Finally, we employed CPU/GPU collaborative parallel prestack time migration technology to analyze the obtained seismic data for geothermal resource evaluation. The favorable areas of karst fissure heat storage in Middle–Upper Proterozoic Jixianian and Paleozoic Cambrian–Ordovician rocks were inferred together with two preferred recommended exploration holes.展开更多
The western segment of the Main Tianshan shear zone(MTSZ)branches into three major dextral strike-slip shear zones in the Borohoro Ranges,northwestern China.Mylonitic rocks within these zones exhibit vertical foliatio...The western segment of the Main Tianshan shear zone(MTSZ)branches into three major dextral strike-slip shear zones in the Borohoro Ranges,northwestern China.Mylonitic rocks within these zones exhibit vertical foliations,subhorizontal lineations,and dextral kinematics.The microstructures and CPO patterns of calcite and quartz in the tectonites suggest shearing at temperatures of 200℃ to 500℃ or above.The amount of dextral displacement along the zones is less than 100 km.LA-ICP-MS U-Pb dating of zircons from some pre-kinematic granites gave ages of 364-325 Ma and 316 Ma,and zircons from a syn-kinematic leucogranite gave an age of 291 Ma.We propose that dextral shearing along the MTSZ started in the earliest Permian.Our data indicate that collision between the Yili and Junggar plates might have finished before 325 Ma or 316 Ma,with a tectonic transformation from 325 Ma to 300 Ma,resulting in intracontinental transpression from 300 Ma or 291 Ma.We suggest that the formation of the Kazakhstan orocline(KO)took place in two stages,with the early stage of bending driven by convergence related to oblique subduction,and the late stage possibly associated with lateral disarticulation as a result of the dextral strike-slip shear zones.展开更多
Earth models are important tools for support of decision making processes for optimal exploitation of subsurface resources. For geosteering and other real-time processes where time is a major constraint, effective mod...Earth models are important tools for support of decision making processes for optimal exploitation of subsurface resources. For geosteering and other real-time processes where time is a major constraint, effective model management is decisive for optimal decision support. During drilling, subsurface information is received which should optimally be used to modify the 3D earth model. Today this model is typically not altered during the operation. We discuss the principles of a novel method that enables a populated earth model grid to be locally modified when the topology (connectivity) of the geological structure is locally altered. The method also allows local updates of the grid resolution. The modelled volume is split into closed regions by the structural model. Each region is individually discretized and obtains its own subgrid. Properties are stored in separate functions, e.g. for each layer, and transferred into each subgrid via a mapping. A local update of the geological structure implies that only subgrids in regions that are directly affected by the updated structure must be discarded and rebuilt, and the rest of the populated earth model grid is retained. Our focus is on decision support for optimal well placement while geosteering. The proposed method aims to manage multiple model realizations that are never fixed and always locally updated with the most recent measurements and interpretations in real-time, and where each realization is always kept at an optimal resolution.展开更多
In the Gulf of Mexico and adjacent landmasses,faults are very complex,and their distribution is closely related to plate tectonics,ocean-land boundary,and former structure.The plane position of the faults can be ident...In the Gulf of Mexico and adjacent landmasses,faults are very complex,and their distribution is closely related to plate tectonics,ocean-land boundary,and former structure.The plane position of the faults can be identified by the maximum characteristic of the vertical derivative of the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly.The apparent depth of the faults is inverted by the Bouguer gravity anomaly curvature property.Based on tectonic evolutionary processes and the plane distribution and apparent depth characteristics of the faults,a complete fault system for the Gulf of Mexico and adjacent areas has been established,including 102 faults.The apparent depths of 33 first-class faults are 16-20 km and for 69 second-class faults are 12-16 km.The F_(1-2)and F_(1-3)subduction fault zones are two caused by the subduction of the Cocos Plate into the old Yucatan and Chorti landmasses;F_(1-11)and F_(1-12)fault zones extend westward to the coast of Guatemala and do not extend into the continent;F_(1-17)and F_(1-20)faults,which control the boundary of the oceanic crust,do not extend southward into the continent.The fault system,which radiates in a"fan-shaped"structure as a whole,unfolds to the northeast.Faults of different nature and sizes are distributed in the Cocos Plate subduction zone,Continental,Gulf of Mexico,Yucatan old landmass and Caribbean Plate in NW,NNW,NS,NE and NEE directions.In the Gulf of Mexico region,the fault system is a comprehensive reflection of former tectonic movements,such as plate movement,drift of old landmasses and expansion of oceanic crusts.The first-class faults control the plate and ocean-continental boundaries.The second-class faults are subordinate to the first-class faults or related to the distribution of different sedimentary layers.展开更多
Taking the Xutuan coal mine as an example, based on the temperature measurement data, combined with the geological background of the study area, this paper analyzes the distribution, thermal evolution, formation mecha...Taking the Xutuan coal mine as an example, based on the temperature measurement data, combined with the geological background of the study area, this paper analyzes the distribution, thermal evolution, formation mechanism and influencing factors of the deep geothermal field in the study area. Combined with previous research results and field temperature measurement data, the research results show that the temperature gradient of Xutuan coal mine varies in the range of 2.65<span style="white-space:nowrap;">°</span>C/hm - 3.15<span style="white-space:nowrap;">°</span>C/hm, most of which are 1.6<span style="white-space:nowrap;">°</span>C/hm - 3.0<span style="white-space:nowrap;">°</span>C/hm, which belongs to the normal area with relatively stable geothermal gradient. The northern part of the study area is more developed than the southern part. The minimum geothermal gradient is 2.65<span style="white-space:nowrap;">°</span>C/hm, and the geothermal gradient gradually increases from north to south;the geothermal gradient is negatively correlated with the buried depth within a certain depth range. Roughly taking the depth of 200 - 350 m as the dividing line, the temperature increases with the increase of depth, showing a good linear trend and the characteristics of conductive heating. The main influencing factor of the geothermal field in the study area is the geological structure, which is greatly affected by the fault structure. Followed by lithological changes and groundwater activities, the flow of the four waters has a certain control effect on the shallow geothermal field distribution.展开更多
The main objective of this study was to investigate copper-Nickle-Iron bearing rocks of the northern Kenya, and understand their mode of formation. The area of study is bounded by latitudes 2º52'00"N...The main objective of this study was to investigate copper-Nickle-Iron bearing rocks of the northern Kenya, and understand their mode of formation. The area of study is bounded by latitudes 2º52'00"N and 1º52'00"N and longitudes 37º19'00"E and 37º36'00"E, South West of Marsabit town. The methods involved geological field mapping between September, 2020 and December 2020. Elemental analyses of the samples were done using an XRF. Pearsonian correlation on the analyzed elements was done using Oasis Montaj 8.4. Fabric8 software was used to analyze structural data. The area comprises metamorphic, igneous and sedimentary rocks. Metamorphic rocks include biotite hornblende gneisses, biotite gneisses, biotite muscovite gneisses and marbles. Basalts of different mineralogy were also found in the area. Colluvium and alluvium sediments were found covering some of the metamorphic rocks in some areas. Malachite occurs in gneisses in the central part of the area. The area has undergone deformation, which includes jointing and folding. The fold axis trend in the North-South direction and plunges to the southern part of the area. Correlation of the elements shows that there is a positive correlation of Copper-Nickel-Iron. This indicates similar mode of delivery within the host rocks. Kriging indicates spatial distribution of these elements within the study area. The average size of distribution can easily be computed from the maps produced by kriging.展开更多
Carbon dioxide(CO_(2))geological utilization and storage(CGUS)is the key link of CO_(2)capture,utilization,and storage(CCUS).The accurate characterization of the geological body structure is a vital prerequisite of CG...Carbon dioxide(CO_(2))geological utilization and storage(CGUS)is the key link of CO_(2)capture,utilization,and storage(CCUS).The accurate characterization of the geological body structure is a vital prerequisite of CGUS.This paper gives a review of the multi-scale three-dimensional geological structure characterization and site selection of CO_(2)storage.It shows that there is a lack of systematic and high-precision methods for transparency characterization of multi-scale three-dimensional engineering geological structure and hydrogeological structure of a CO_(2)storage site.There is no clear understanding of the fracture evolution and gas-liquid migration process of multi-scale geological body structure under the disturbance of CO_(2)injection.There is a lack of sufficient quantitative methods for the dynamic evaluation of CO_(2)geological storage potential.The geological suitability evaluation method for site selection of CO_(2)storage is rough and has poor applicability,which is difficult to satisfy the urgent needs of CGUS site selection in the whole process of CO_(2)sequestration industrialization in the future.Thus,it is required to conduct studies on the transparency characterization of geological body structure and intelligent site selection for CO_(2)storage,which is of great importance for CGUS engineering practice.展开更多
The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digit...The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digital elevation models integrated with field and petrographic observations to characterize the architecture of the≥17,000 km2 Mesoproterozoic Kunene Complex(KC)anorthosite suite in Angola and Namibia.Images of false colour composite bands 6,4 and 1 and band ratios 4/2(ferric minerals),6/5(ferrous minerals)and 6/7(OH-bearing minerals),as well as assessment of the PCA and MNF matrices of eigenvectors and eigenvalues from Landsat 8 data using available spectral libraries,have substantially improved the interpretation of the Kunene Complex rock types and structures.The dataset shows that the reflectance signature of KC anorthositic rocks is primarily a function of the degree of metasomatism,which is most significant in olivine-poor rock types.The weathering intensity of the olivine-bearing anorthosite substrate is another control on the remote sensing signal.Our remote sensing and field-based approach has enabled us to divide the KC anorthosite suite into six distinct spectral and architecture domains and at least four distinct magmatic plutons when considering available high-precision geochronological data.The northernmost pluton(ca.1380 Ma)of massive,olivine-bearing anorthosite shows distinct remote sensing signatures in the band ratio and MNF images marked by the dominance of OH-bearing and subordinate ferric minerals.The central pluton(1412–1400 Ma)is composed of NNE-to N-striking steeply dipping interlayered olivine-bearing and olivinepoor anorthosite,which correspond to ridges of dark-coloured,low albedo rocks with subordinate slightly oxidised ferrous mineral spectral signatures,and valleys of low albedo and OH-bearing mineral spectral signatures.A NNE-striking tectonic zone along a linear belt of KC granite gneiss separates the northern and central plutons.To the south is a NNW-to NNE-striking layered pluton(ca.1390 Ma),marked by olivine-bearing anorthosite that forms ridges and metasomatized olivine-poor and pyroxene-bearing anorthosite that forms valleys.This domain is separated from the similarly layered and E–W-striking Zebra Lobe–Oryeheke anorthosite by a top-to-the north thrust zone.A small domain of ca.1438 Ma olivine-bearing anorthosite sensu lato is situated to the SE of the main Kunene Complex.This work highlights the variability in layered and massive textures,the extent of metasomatism,and the importance of internal tectonic boundaries in the architecture of the Kunene Complex anorthosite suite.Our approach can be applied in other anorthositic terrains and large igneous bodies elsewhere on Earth,especially those where outcrop is poor,or access is inhibited.展开更多
基金Supported by the Petro China Science and Technology Project(2016E-0601,2019B-0503)China National Science and Technology Major Project(2016ZX05003-001)
文摘Based on the latest geological,seismic,drilling and outcrop data,we studied the geological structure,tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the potential hydrocarbon exploration areas in deep layers.During key tectonic periods,the southwestern Sichuan fold-thrust belt developed some characteristic strata and structural deformation features,including the Pre-Sinian multi-row N-S strike rifts,step-shaped platform-margin structures of Sinian Dengying Formation,the western paleo-uplift in the early stage of Late Paleozoic,the Late Paleozoic–Middle Triassic carbonate platform,foreland slope and forebulge during Late Triassic to Cretaceous,and Cenozoic multi-strike rejuvenated fold-thrusting structures.The fold-thrust belt vertically shows a double-layer structural deformation controlled by the salt layer in the Middle Triassic Leikoupo Formation and the base detachment layer at present.The upper deformation layer develops the NE-SW strike thrusts propagating toward basin in long distance,while the deeper deformation layer had near north-south strike basement-involved folds,which deformed the detachment and thrusting structures formed earlier in the upper layer,with the deformation strength high in south part and weak in north part.The southern part of the fold-thrust belt is characterized by basement-involved fold-thrusts formed late,while the central-northern part is dominated by thin-skin thrusts in the shallow layer.The Wuzhongshan anticlinal belt near piedmont is characterized by over-thrust structure above the salt detachment,where the upper over-thrusting nappe consists of a complicated fold core and front limb of a fault-bend fold,while the deep layer has stable subtle in-situ structures.Favorable exploration strata and areas have been identified both in the upper and deeper deformation layers separated by regional salt detachment,wherein multiple anticlinal structures are targets for exploration.Other potential exploration strata and areas in southwestern Sichuan fold-thrust belt include the deep Sinian and Permian in the Wuzhongshan structure,pre-Sinian rifting sequences and related structures,platform-margin belt of Sinian Dengying Formation,and Indosinian paleo-uplift in the east of the Longquanshan structure.
基金The Construction S&T Project of the Department of Transportation of Sichuan Province(Grant No.2023A02)the National Natural Science Foundation of China(No.52109135).
文摘The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.
基金National Postdoctoral Program for Innovative Talent of China,Grant/Award Number:BX20200191National Natural Science Foundation of China,Grant/Award Number:52079068The State Key Laboratory of Hydroscience and Hydraulic Engineering,Grant/Award Number:2021-KY-04。
文摘The investigation of the in situ stress distribution has always been a key condition for engineering design of deep tunnels and analysis of surrounding rock stability.In this paper,a comprehensive judgment method coupled with pressure/tension(P/T)axis mechanism and geological structure is proposed to invert the in situ stress in the Duoxiongla tunnel in Tibet.In the process of TBM tunnel excavation,3887 groups of microseismic events were collected by means of microseismic monitoring technology.By studying the temporal and spatial distribution of 3887 groups of microseismic events,42 groups of microseismic data were selected for in situ stress inversion.Then the focal mechanisms of 42 groups of microseisms were inverted.Combined with the analysis of the previous geological survey,the inversion results of the in situ stress were analyzed.According to the focal mechanism of the tunnel area,the linear in situ stress inversion method was used to invert the in situ stress in the source area.Finally,according to the PTGS(pressure/tension axis mechanism and geological structure)comprehensive judgment method proposed in this paper,the in situ stress of the tunnel microseismic region was determined.The results show that there are mainly three groups of fissures and joint surfaces in the tunnel area,and the in situ stress is dominated by the horizontrun tectonic stress;the main driving force of the rupture surface in the excavation process of Duoxiongla tunnel is the horizontal tectonic stress;the distribution of the maximum and minimum principal stress obtained by the inversion is consistent with the distribution of the P/T axis;combined with the linear in situ stress inversion method and the comprehensive judgment of PTGS,the azimuth and dip angles of the three principal stresses are finally determined as N90.71°E,4.06°,N5.35°W,3.06°,and N8.10W,85.32°,respectively.The study verifies the feasibility of microseismic inversion of in situ stress.
基金provided by the Talent Training Project of the National Natural Science Foundation of China (No.J0730534)the National Natural Science Foundation of China (No.40902093)+1 种基金the Morning Light Plan of the Shanghai Educational Development Foundation (No.2007CG34)the Open Foundation of the Shanghai Key Laboratory of Urbanization and Ecological Restoration (No.200803)
文摘Uncertainty in 3D geological structure models has become a bottleneck that restricts the development and application of 3D geological modeling.In order to solve this problem during periods of accuracy assessment,error detection and dynamic correction in 3D geological structure models,we have reviewed the current situation and development trends in 3D geological modeling.The main context of uncertainty in 3D geological structure models is discussed.Major research issues and a general framework system of uncertainty in 3D geological structure models are proposed.We have described in detail the integration of development practices of 3D geological modeling systems,as well as the implementation process for uncertainty evaluation in 3D geological structure models.This study has laid the basis to build theoretical and methodological systems for accuracy assessment and error correction in 3D geological models and can assist in improving 3D modeling techniques under complex geological conditions.
基金Supported by the National Natural Science Foundation of China Enterprise Innovation and Development Joint Fund Project(U19B6003-01)Scientific research and technology development project of China National Petroleum Corporation(2021DJ3103).
文摘Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin.(1)The geological structure of the Termit Basin is represented as a narrow rift basin,with development of series of structural styles in extensional,extensional strike-slip and compressional stress setting.On plane,it is narrow in the north and wide in the south,and transitions from graben to half-graben from north to south;it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south.(2)Before the Cretaceous,a series of hidden faults developed in the West African rift system,which laid the foundation for the development location and distribution direction of the Termit Basin;during the Cretaceous to Paleogene periods,the basin experienced two phases of rifting in Early Cretaceous and Paleogene,which controlled the initial structure and current structural shape of the basin respectively;during the Neogene to Quaternary,the basin was subjected to weak transformation.(3)In the Precambrian,the Pan-African movement gave rise to a narrow and long weak zone within the African plate,which provided the pre-existing structural conditions for the formation of the Termit Basin.In the Early Cretaceous,affected by the South Atlantic rifting,the Pan African weak zone was reactivated,resulting in the first stage of rifting and the basic structural framework of the Termit Basin.In the Paleogene,affected by the subduction and convergence of the Neo-Tethys Ocean,the African-Arabian plate extended in near E-W trending,and the Termit Basin experienced the second stage of rifting.The oblique extension in this period caused intense structural differentiation,and the current structural pattern of alternate uplifts and depressions took shape gradually.
基金National Key Research Development Project(95-13-02-02).Contribution No.LC2000052,Lanzhou Institute of Seismology,China SeismologicalBureau.
文摘The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geological data. The main results are summarized as follows: ( The geotectonic subdivisions and the characteristics of main deep and large faults in the northeastern margin of the Qinghai-Tibetan plateau are presented; ( The general features of the Moho are obtained mainly based on artificial seismic sounding data; ( There exists well corresponding relation between surface faults and some features of the Moho, which suggests that such complex crustal structure might be the preparation environment of strong earthquakes.
基金funded by the National Key Research and Development Program of China(Grant No.2019YFB1504101)the Natural Science Foundation of Hebei Province,China(Grant No.D2021504041)。
文摘As typical carbonate geothermal reservoirs with low porosity in northern China,the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration.The Jixianian System comprises the Gaoyuzhuang,Yangzhuang,Wumishan,Hongshuizhuang,and Tieling formations.The characteristics,formation periods,and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops,cores,thin sections,and image logs.The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40°to 70°and the fracture porosity increases linearly with an increased fracture aperture.Within the same tectonic setting and stress field,the lithology and layer thickness are the dominant factors governing the development of tectonic fractures,which are the most developed in dolomites and thin layers.Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients.The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets:NNW-SSE and NNE-SSW oriented‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement;NE-SW-oriented shear fractures,formed in episode B of the Yanshanian Movement,occurred at the Early Cretaceous;nearly E-W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene,and NEE-SW-oriented shear fractures formed during the Himalayan movement.
基金the National Natural Science Foundation of China-Henan Talent Training Joint Foundation,which funded this study(Grant No.U1504404)。
文摘The spatial prediction of geothermal sites along the southeast side of Taihang Mountain in the Tangyin rift is a critical goal in the development of renewable energy resources in cities such as Hebi in Henan province,which has significant potential for geothermal energy production due to the existence of deep faults and Cenozoic volcano.The study aimed to delineate areas with high geothermal manifestations for detailed geothermal exploration and well-test drilling.To define favorable zones for geothermal potentiality,multi-source datasets were chosen to generate evidence thematic layers that demonstrate the distribution of geothermal anomalies such as geologic maps,structural maps,Land Surface Temperature maps(LST),and hydrothermal mineral alterations maps.The remote sensing and Geographical Information System(GIS)approaches were integrated to map fossil geothermal manifestations and appraise the promising geothermal zones from Landsat 8 OLI/TIRS and Advanced Spaceborne Thermal Emission and Reflection Radiometer-Digital Elevation Model(ASTER-DEM)dataset using the Analytic Hierarchy Process(AHP),which is one of the Mult-criteria Decision Making methods.Results show LST values ranging from 22.6℃ to 45.4℃,with the highest values found along the faults and volcanic areas.The hydrothermal alteration minerals discriminated from band ratios of 4/2,6/5,and 6/7 for iron oxide,ferrous minerals,and clays reveal the presence of high amount of montmorillonite and illite minerals along the faults and volcanoes which are related to hot fluid circulation from subsurface.Structural analysis shows that the major structural trend follows the NNE Tangdong and Tangxi faults,with high density on the west side of the Tangxi fault where there is good exposure of outcrop but less fault density on the east side due to sedimentation in a low land which may conceal geological structures.Lastly,all the thematic layers of geothermal factors were reclassified,ranked,and integrated by the weight overlay logic model based on the influence of geothermal suitability to map potential areas for geothermal resources whereby 5 zones were obtained ranging from very poor to very good.The promising potential sites are mostly found along the highly deep structures of the major Tangxi fault crosscutting the permeable lithology of carbonate rocks and around the Hebi volcanoes.The distribution of hot springs and geothermal wells of the Hebi field were correlated and verified against the potential geothermal anomalies map.The overall integrated method proposes an advanced technique for designing the Tangyin rift’s exploration plan and development actions for geothermal resources utilization,which can be used for exploration of any unveiling geothermal potential sites.
基金This research is supported by National Key Research and Development Project,Ministry of Science and Technology of the People’s Republic of China(2018YFC1504700).
文摘Utilization of urban underground space has become a vital approach to alleviate the strain on urban land resources,and to optimize the structure and pattem of the city.It is also very important to improve the city environment,build livable city and increase the capacity of the city.Based on the analysis of existing evaluation methods and their problems,a method for evaluating underground space resources based on a negative list of adverse factors affecting underground space development is proposed,to be primarily used in urban planning stages.A list of the adverse factors is established,including limiting factors,constraining factors and influencing factors.Taking Xi'an as an example,using a geographical information system platform,a negative list of adverse factors for the underground space resources in Xi'an City are evaluated,and preventive measures are proposed.Natural resources,exploitable resources,and the potential growth of exploitable underground space resources are evaluated.Underground space assessment in the different development stages of the city,collaborative utilization and safety evaluation for multiple subsurface resources,environmental impact and assessment,as well as evaluation methods based on big data and intelligent optimization algorithms are all discussed with the aim of serving city planning and construction.
文摘The Baiyun cave is a 380 m long karst cave in the Naigu Shilin, situated 70 km southeast of Kunming,Yunnan Province, China. The prevailing orientations of the cave passages are N110°-120°E and N0°-10°W and those of the fissures in the cave are N30°-40°W and N20°-30°W. The cave is developed in the thick-bedded Lower Permian Qixia Formation. The cave has an active water flow and is currently at the near water-table stage. There are large amounts of different infills of cave sediments. The cave shows different stages of paragenesis. The palaeomagnetic analysis of cave sediments shows that their ages are younger than 780 ka B.P. (the Brunhes Chron). The upper part of the sampled profile belongs to the reverse Blake event (112.3-117.9 ka B.P.). The formation of the Baiyun cave is directly connected with the development of the Naigu Shilin. The formation of karst underground and surface features depends on the regional tectonic deformation and the Cenozoic extension of the study area.
基金The authors are grateful to the financial support from National Science and Technology Major Project of China:Demonstration project of coordinated exploitation of coalbed methane and coal in key coal mines of Shanxi province(2016ZX05067)National Natural Science Foundation of China(5187431451904311).
文摘The thermal effect caused by deep magma intrusion can not only accelerate the metamorphism of coal body,but also bring additional thermal field that changes the mechanical environment of coal seams,thereby affecting the permeability of coal seams.Different from shallow coal resources,deep coal resources are in a mechanical environment characterized by limited stress and strain.Thus,the thermal effect has a more significant influence on the distribution and permeability characteristics of deep coal seams.In this study,the evolution history of highly metamorphic coal seams in Yangquan mining area was analyzed,and the main effect of magmatic activity on coal seams was obtained.Based on the determined vitrinite reflectance data of typical mines in Yangquan mining area,the maximum paleotemperature was calculated by adopting the Barker’s method.Furthermore,the paleotemperature distribution in Yangquan mining area was summarized,and its relationship with the metamorphic degree was acquired.Then,a new permeability model considering the thermal strain was proposed to analyze the permeability evolution in deep coal seams at different ground temperatures.Finally,through a combination of the results of gas pressure and outburst number in Sijiazhuang Mine,Yangquan No.5 Mine and Xinjing Mine,the influence of ground temperature on the gas outburst risk in Yangquan mining area was explored.The following conclusions were drawn:The maximum paleotemperature in Yangquan area can be 303C.In addition,the paleotemperature in the south is higher than that in the north of Yangquan mining area.The various temperatures at different depths bring about different degrees of thermal stress to different coal seams,leading to different strains.Under the fixed displacement boundary conditions in the deep,the coal seam folds and bends to varying degrees.Moreover,the difference in the ground temperature raises the a value of coal seams and lowers the permeability,which promotes the formation of gas-rich zones and increases the risk of coal seam outburst.The research results can help mines to make proper gas disaster prevention plan for different zones.
基金supported by Department of Science and Technology of Guangdong Provinces (No. 2019ZT08G315)Natural Science Foundation of China (No. 52174083)+2 种基金Sichuan University, State Key Lab Hydraul & Mt River Engn Foun (No. SKHL2021)the S&T (Science and Technology) Program of Hebei (No. 20374201D)DOE Laboratory of Deep Earth Science and Engineering (Nos. DESE202102, DESE202108)。
文摘Geothermal resources exist in complex and comprehensive geological settings. In the current study, we proposed a CPU/GPU collaborative parallel prestack time migration methodology for geothermal resource exploration. First, seismic geological conditions in Xian County were obtained based on an analysis of drill cores for further seismic evaluation. Then,combined with the analysis of two-dimensional seismic data in the adjacent area, a test section with three seismic survey lines were designed to explore the geological structure of the study area. In the study area, the seismic data were derived through the multiple coverage reflection wave exploration method with explosive ignition in deep wells and high coverage frequency observations. Finally, we employed CPU/GPU collaborative parallel prestack time migration technology to analyze the obtained seismic data for geothermal resource evaluation. The favorable areas of karst fissure heat storage in Middle–Upper Proterozoic Jixianian and Paleozoic Cambrian–Ordovician rocks were inferred together with two preferred recommended exploration holes.
基金financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China(Grant No.2014CB448000)the National Natural Science Foundation of China(Grant Nos.41772207,41422206)。
文摘The western segment of the Main Tianshan shear zone(MTSZ)branches into three major dextral strike-slip shear zones in the Borohoro Ranges,northwestern China.Mylonitic rocks within these zones exhibit vertical foliations,subhorizontal lineations,and dextral kinematics.The microstructures and CPO patterns of calcite and quartz in the tectonites suggest shearing at temperatures of 200℃ to 500℃ or above.The amount of dextral displacement along the zones is less than 100 km.LA-ICP-MS U-Pb dating of zircons from some pre-kinematic granites gave ages of 364-325 Ma and 316 Ma,and zircons from a syn-kinematic leucogranite gave an age of 291 Ma.We propose that dextral shearing along the MTSZ started in the earliest Permian.Our data indicate that collision between the Yili and Junggar plates might have finished before 325 Ma or 316 Ma,with a tectonic transformation from 325 Ma to 300 Ma,resulting in intracontinental transpression from 300 Ma or 291 Ma.We suggest that the formation of the Kazakhstan orocline(KO)took place in two stages,with the early stage of bending driven by convergence related to oblique subduction,and the late stage possibly associated with lateral disarticulation as a result of the dextral strike-slip shear zones.
文摘Earth models are important tools for support of decision making processes for optimal exploitation of subsurface resources. For geosteering and other real-time processes where time is a major constraint, effective model management is decisive for optimal decision support. During drilling, subsurface information is received which should optimally be used to modify the 3D earth model. Today this model is typically not altered during the operation. We discuss the principles of a novel method that enables a populated earth model grid to be locally modified when the topology (connectivity) of the geological structure is locally altered. The method also allows local updates of the grid resolution. The modelled volume is split into closed regions by the structural model. Each region is individually discretized and obtains its own subgrid. Properties are stored in separate functions, e.g. for each layer, and transferred into each subgrid via a mapping. A local update of the geological structure implies that only subgrids in regions that are directly affected by the updated structure must be discarded and rebuilt, and the rest of the populated earth model grid is retained. Our focus is on decision support for optimal well placement while geosteering. The proposed method aims to manage multiple model realizations that are never fixed and always locally updated with the most recent measurements and interpretations in real-time, and where each realization is always kept at an optimal resolution.
基金granted by the National Science and Technology Major Project of China(Grant No.2017ZX05032-003)the National Key R&D Program of China(Grant No.2017YFC0602202)。
文摘In the Gulf of Mexico and adjacent landmasses,faults are very complex,and their distribution is closely related to plate tectonics,ocean-land boundary,and former structure.The plane position of the faults can be identified by the maximum characteristic of the vertical derivative of the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly.The apparent depth of the faults is inverted by the Bouguer gravity anomaly curvature property.Based on tectonic evolutionary processes and the plane distribution and apparent depth characteristics of the faults,a complete fault system for the Gulf of Mexico and adjacent areas has been established,including 102 faults.The apparent depths of 33 first-class faults are 16-20 km and for 69 second-class faults are 12-16 km.The F_(1-2)and F_(1-3)subduction fault zones are two caused by the subduction of the Cocos Plate into the old Yucatan and Chorti landmasses;F_(1-11)and F_(1-12)fault zones extend westward to the coast of Guatemala and do not extend into the continent;F_(1-17)and F_(1-20)faults,which control the boundary of the oceanic crust,do not extend southward into the continent.The fault system,which radiates in a"fan-shaped"structure as a whole,unfolds to the northeast.Faults of different nature and sizes are distributed in the Cocos Plate subduction zone,Continental,Gulf of Mexico,Yucatan old landmass and Caribbean Plate in NW,NNW,NS,NE and NEE directions.In the Gulf of Mexico region,the fault system is a comprehensive reflection of former tectonic movements,such as plate movement,drift of old landmasses and expansion of oceanic crusts.The first-class faults control the plate and ocean-continental boundaries.The second-class faults are subordinate to the first-class faults or related to the distribution of different sedimentary layers.
文摘Taking the Xutuan coal mine as an example, based on the temperature measurement data, combined with the geological background of the study area, this paper analyzes the distribution, thermal evolution, formation mechanism and influencing factors of the deep geothermal field in the study area. Combined with previous research results and field temperature measurement data, the research results show that the temperature gradient of Xutuan coal mine varies in the range of 2.65<span style="white-space:nowrap;">°</span>C/hm - 3.15<span style="white-space:nowrap;">°</span>C/hm, most of which are 1.6<span style="white-space:nowrap;">°</span>C/hm - 3.0<span style="white-space:nowrap;">°</span>C/hm, which belongs to the normal area with relatively stable geothermal gradient. The northern part of the study area is more developed than the southern part. The minimum geothermal gradient is 2.65<span style="white-space:nowrap;">°</span>C/hm, and the geothermal gradient gradually increases from north to south;the geothermal gradient is negatively correlated with the buried depth within a certain depth range. Roughly taking the depth of 200 - 350 m as the dividing line, the temperature increases with the increase of depth, showing a good linear trend and the characteristics of conductive heating. The main influencing factor of the geothermal field in the study area is the geological structure, which is greatly affected by the fault structure. Followed by lithological changes and groundwater activities, the flow of the four waters has a certain control effect on the shallow geothermal field distribution.
文摘The main objective of this study was to investigate copper-Nickle-Iron bearing rocks of the northern Kenya, and understand their mode of formation. The area of study is bounded by latitudes 2º52'00"N and 1º52'00"N and longitudes 37º19'00"E and 37º36'00"E, South West of Marsabit town. The methods involved geological field mapping between September, 2020 and December 2020. Elemental analyses of the samples were done using an XRF. Pearsonian correlation on the analyzed elements was done using Oasis Montaj 8.4. Fabric8 software was used to analyze structural data. The area comprises metamorphic, igneous and sedimentary rocks. Metamorphic rocks include biotite hornblende gneisses, biotite gneisses, biotite muscovite gneisses and marbles. Basalts of different mineralogy were also found in the area. Colluvium and alluvium sediments were found covering some of the metamorphic rocks in some areas. Malachite occurs in gneisses in the central part of the area. The area has undergone deformation, which includes jointing and folding. The fold axis trend in the North-South direction and plunges to the southern part of the area. Correlation of the elements shows that there is a positive correlation of Copper-Nickel-Iron. This indicates similar mode of delivery within the host rocks. Kriging indicates spatial distribution of these elements within the study area. The average size of distribution can easily be computed from the maps produced by kriging.
基金supported by the National Natural Science Foundation of China(Grant No.42141009)the Key Research Program of the Institute of Geology and Geophysics,CAS(Grant No.IGGCAS-202201).
文摘Carbon dioxide(CO_(2))geological utilization and storage(CGUS)is the key link of CO_(2)capture,utilization,and storage(CCUS).The accurate characterization of the geological body structure is a vital prerequisite of CGUS.This paper gives a review of the multi-scale three-dimensional geological structure characterization and site selection of CO_(2)storage.It shows that there is a lack of systematic and high-precision methods for transparency characterization of multi-scale three-dimensional engineering geological structure and hydrogeological structure of a CO_(2)storage site.There is no clear understanding of the fracture evolution and gas-liquid migration process of multi-scale geological body structure under the disturbance of CO_(2)injection.There is a lack of sufficient quantitative methods for the dynamic evaluation of CO_(2)geological storage potential.The geological suitability evaluation method for site selection of CO_(2)storage is rough and has poor applicability,which is difficult to satisfy the urgent needs of CGUS site selection in the whole process of CO_(2)sequestration industrialization in the future.Thus,it is required to conduct studies on the transparency characterization of geological body structure and intelligent site selection for CO_(2)storage,which is of great importance for CGUS engineering practice.
基金supported by a National Research Foundation(NRF)Thuthuka Grant(TTK14052367805)the DSI-NRF Centre of Excellence for Integrated Mineral and Energy Resource Analysis(DSI-NRF CIMERA)。
文摘The quasi-monomineralic composition and huge spatial extent of massif-type anorthosites make detecting lithological regions and boundaries challenging.We use processed Landsat 8 OLI multispectral images and ALOS digital elevation models integrated with field and petrographic observations to characterize the architecture of the≥17,000 km2 Mesoproterozoic Kunene Complex(KC)anorthosite suite in Angola and Namibia.Images of false colour composite bands 6,4 and 1 and band ratios 4/2(ferric minerals),6/5(ferrous minerals)and 6/7(OH-bearing minerals),as well as assessment of the PCA and MNF matrices of eigenvectors and eigenvalues from Landsat 8 data using available spectral libraries,have substantially improved the interpretation of the Kunene Complex rock types and structures.The dataset shows that the reflectance signature of KC anorthositic rocks is primarily a function of the degree of metasomatism,which is most significant in olivine-poor rock types.The weathering intensity of the olivine-bearing anorthosite substrate is another control on the remote sensing signal.Our remote sensing and field-based approach has enabled us to divide the KC anorthosite suite into six distinct spectral and architecture domains and at least four distinct magmatic plutons when considering available high-precision geochronological data.The northernmost pluton(ca.1380 Ma)of massive,olivine-bearing anorthosite shows distinct remote sensing signatures in the band ratio and MNF images marked by the dominance of OH-bearing and subordinate ferric minerals.The central pluton(1412–1400 Ma)is composed of NNE-to N-striking steeply dipping interlayered olivine-bearing and olivinepoor anorthosite,which correspond to ridges of dark-coloured,low albedo rocks with subordinate slightly oxidised ferrous mineral spectral signatures,and valleys of low albedo and OH-bearing mineral spectral signatures.A NNE-striking tectonic zone along a linear belt of KC granite gneiss separates the northern and central plutons.To the south is a NNW-to NNE-striking layered pluton(ca.1390 Ma),marked by olivine-bearing anorthosite that forms ridges and metasomatized olivine-poor and pyroxene-bearing anorthosite that forms valleys.This domain is separated from the similarly layered and E–W-striking Zebra Lobe–Oryeheke anorthosite by a top-to-the north thrust zone.A small domain of ca.1438 Ma olivine-bearing anorthosite sensu lato is situated to the SE of the main Kunene Complex.This work highlights the variability in layered and massive textures,the extent of metasomatism,and the importance of internal tectonic boundaries in the architecture of the Kunene Complex anorthosite suite.Our approach can be applied in other anorthositic terrains and large igneous bodies elsewhere on Earth,especially those where outcrop is poor,or access is inhibited.
