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Ma C.-Y.,Central South University | Ma C.-Y.,Non ferrous Resources and Geologic Disasters Prospecting Emphases Laboratory of Hunan | Liu J.-X.,Central South University | Liu J.-X.,Non ferrous Resources and Geologic Disasters Prospecting Emphases Laboratory of Hunan | And 5 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2017

We present a global weak form element free method (EFM) for simulation of direct current resistivity. EFM is a new numerical simulation method developed on the basis of finite element method (FEM). The key point of this method is the absence of elements and the nodes free from the elemental restraint, which makes it very flexible and the pre-processing simple. It utilizes the nodes of local support domain to construct shape functions to achieve the accurate approximations of the local domain. Approximations of EFM are of high order and boundary conditions are enforced simply, because the radial point interpolation method (RPIM) is used to construct shape function. Therefore, EFM is more suitable to simulate complex models than FEM. First, the boundary value problem and the corresponding variational problem of direct current resistivity forward simulation are derived starting from the partial differential equation of current field. Second, the construction of RPIM shape function is introduced in details. Third, equations of the global weak form EFM for direct current resistivity is derived in details based on RPIM shape function. Then, a Fortran program is written according to the equations. By forward simulation with this program, a homogeneous half-space model was used to verify our element free approach. At the same time, we compared the solutions of EFM and FEM in details which shows that the solutions of EFM are more accurate. Furthermore, the solutions indicate the correctness and effectiveness of the EFM for direct current resistivity forward simulation. Finally, we improve the simulation accuracy successfully by refining nodes arbitrarily, and the solutions of EFM forward simulation for complex geoelectric models show that EFM has a high degree of flexibility. © 2017, Science Press. All right reserved.

Bai D.,Hunan Institute of Geology Survey | Xiong X.,Hunan Institute of Geology Survey | Yang J.,Hunan Institute of Geology Survey | Zhong X.,Hunan Institute of Geology Survey | Jiang W.,Hunan Institute of Geology Survey
Geotectonica et Metallogenia | Year: 2015

The basin-mountain transition zone between the Xuefeng Orogen and the Sichuan Basin is divided into the western comb-like fold belt and the eastern trough-like fold belt by the Qiyueshan fault. There exist different ideas about the formation mechanism of the folds in the basin-mountain transition zone. Among these points of view, the "Xuefeng pushing-westward model" is the most influential and widely held. The model put forward that the comb-like folds and trough-like folds were formed by multi-layer westward detachment-thrusting of the sedimentary cover and progressive compression for the driving of the Xuefeng Orogen. Taking the Sangzhi-Shimen synclinorium and the folds in the Yuanhe area for examples, the authors studied the characteristics and dynamic mechanisms of the folds in the area east of the Qiyueshan fault by measured tectonic sections, geophysical profiles and regional geological data, and reached the following conclusions: (1) The folds in the Sangzhi-Shimen synclinorium are "complex fold" and were formed mainly in late Middle Triassic. The folds in the Yuanhe area are typical trough-like folds related mainly to the NWW-directed compression in Late Jurassic to Early Cretaceous. (2) The folds were mainly controlled by the whole horizontal contraction of autochthon including folded basement and cover in regional compressional regime, and by the resultant thrusting and detachment. Deformation of the folded basement in the Sangzhi-Shimen synclinorium shows as thrust faults, while the deformation of the folded basement in the Yuanhe area exhibits as detachment anticline. (3) The deformation mechanism as whole horizontal contraction in regional compression can explain some important geological facts such as that the axial surfaces of folds and the thrust faults don't show a polarity of east or southeast dipping, the Xuefeng Orogen didn't thrust on a large scale to the western fold belt and there occurred a giant whole tectonic uplift in the basin-mountain transition zone. In contrast, the "Xuefeng pushing-westward model" cannot explain the facts and have the problems such that the cross sections cannot be balanced. © 2015, Science Press. All right reserved.

Bai D.,Hunan Institute of Geology Survey | Zhong X.,Hunan Institute of Geology Survey | Jia P.,Hunan Institute of Geology Survey | Xiong X.,Hunan Institute of Geology Survey
Geotectonica et Metallogenia | Year: 2013

The Jingzhou Basin is a small NE-trending Late Triassic to Middle Jurassic continental basin in the south segment of the Xuefeng orogen. In the Upper Paleozoic and Jurassic sequences, around and inside of the basin respectively, the authors observed lots of small-scale faults and joints of different attitude and kinematic property. Several stress events such as N-S compression, NNE compression, NEE compression, E-W compression, NW compression and NW extension were identified. According to the stratigraphy and crosscutting relationship of the faults and joints as well as the tectonic characteristics of the Jingzhou Basin and regional tectonic settings, the authors defined the tectonic evolution of the area ever since Mesozoic: regional NW compression in late Middle Triassic, N-S compression during Late Triassic to Early Jurassic, NW compression during early to middle of the Middle Jurassic, N-S compression in late Middle Jurassic originated from the sinistral strike-slipping of the NE-to NNE-trending Xupu-Jingzhou fault, regional NE compression and NW extension in Cretaceous, NEE compression during Late Cretaceous to Paleocene originated from the dextral strike-slipping of the Xupu-Jingzhou fault, EW compression during Eocene to Oligocene, and NNE compression in Neogene.

Lei Y.-B.,Central South University | Lei Y.-B.,Hunan Institute of Geology Survey | Lai J.-Q.,Central South University | Wang X.-J.,Central South University | And 3 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014

Hutouya deposit is one of the typical Pb-Zn polymetallic deposits in Qimantage region. This deposit was divided into 4 metallogenic epoches and 7 mineralization stages based on geological characteristics of ore and identification of polished sections and thin slices. There were 16 representative minerals selected from sulfides and measured to determine the values of S and Pb isotopes. The results show that the values of δ(34S) range from +0.6×10-3 to +9.8×10-3, in which the average value is +5.2×10-3, and increase gradually from the edges of intrusions to the distal end of them, while the range of Pb isotope is small, with 38.717-38.261 for 208Pb/204Pb, 15.718-15.560 for 207Pb/204Pb, 19.502-18.476 for 206Pb/204Pb. Associated with characteristics of the ore deposit and the results of the former researchers, the characteristics of S and Pb isotopes were analyzed, and the proportions of Pb in the crust and mantle are estimated to be 0.07-0.22 and 0.78-0.93, respectively. The sources of metallogenic material are speculated from the magmatite that is composed of large ratio of crust matter and small proportion of mantle. The evolution of metallogenic material is that S element has higher proportion of igneous rocks' matter when mineralization is adjacent to magmatite, and with larger percentage of strata in distal area; however, the main materials still originate from intrusions. ©, 2014, Science Press. All right reserved.

Rao J.-R.,Hunan Institute of Geology Survey | Xtao H.-Y.,Hunan Institute of Geology Survey | Liu Y.-R.,Hunan Institute of Geology Survey | Bai D.Y.,Hunan Institute of Geology Survey | Deng Y.-Y.,Hunan Institute of Geology Survey
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2012

Location of the Yangtze-Cathaysia plate convergence zone in Hunan is concerned by investigators and has not coincident recognition for absence of direct evidence. Certainty of the location and trend of the Yangtze-Cathaysia plate convergence zone in Hunan has scientific significance to the tectonic division of South China and basic geology theory. Geophysical features of deep structures turn into essential foundation in certaining location of the plate convergence zone for absence of upper direct evidence. Combined with geoogica data, using deep structure informations provided by regional gravity and magnetic, seismic, magnetotelluric sounding and heat flow data ,this paper reinterprets 3D lithospheric structure of Hunan and South China, and brings new knowledge the tectonic characteristics and the location of the Yangtze-Cathaysia plate convergence zone in Hunan, and about the tectonic characteristics of Jiangnan ancient land. The study consider that the YuanMa-Dongting-Hengyang arc gravitational high is caused by crystalline basemental uplift with paleo-volcanic cone, and infer that there exist paleo-volcanic island-chain along Mayang-Taoyuan-Yiyang-Nanqiao, and hidden residue paleo-volcanic islands along Liuyang-Hengyang, east Hunan. The authors drew the shape of the rigid upper mantle block of Yangtze and Cathaysia paleo-plate; conferred that the Yangtze-Cathaysia intermediate zone were paleo-Jiangxi-Hunan-Guangxi south-China ocean. The paper brings forward recognitions as follow: the Neoproterozoic orogenic belt was continent-arc-island-continent collision orogenic belt; intercontinental hidden residue paleo-volcanic islands in south Hunan are nowadays part of plate merge belt; 3D Lithospheric structural characteristics of Yangtze, Cathaysia block and intermediate zone are absolutely different; there existed paleo-lithospheric subduction zone in middle Jiangxi-Hunan-Guangxi; the lithosphere of middle Hunan is thickest in South China; the northwestern boundary of Yangtze-Cathaysia plate convergence zone was along Xixian-Nanchang-Daweishan-Weishan-Chengbu-Hechi, while the southeastern boundary along Jiangshan-Shaoxing-Xinyu-Pingxiang-Hengdong-Shuangpai-Guilin-Liuzou; plate merge belt between Yangtze and Cathaysia plate are the Qinzhou-Hangzhou juncture in Hunan. ChalingChenzhou fault wasn't the Yangtze-Cathaysia plate convergence zone but Caledonian intraplate thrust fault in Cathaysia plate.

Jiang W.,Hunan Institute of Geology Survey | Tang S.,China University of Geosciences | Gong Y.,Bureau of Coal Geology of Hunan Province | Fan E.,China University of Geosciences | Zhang C.,China University of Geosciences
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2014

Through outcrop observation and cross section measured, together with analytic results like microscope observation, geochemical parameters, pore structure, surface area and methane adsorption isotherm experiments, the geological accumulation characteristics and physical properties of the shale gas were investigated in detail in this article. Results show that the shale is characterized with wide distribution area, a great thickness, high organic content (an average of 1.87%), and high organic thermal evolution degree (above 1.0%). At the same time, a large variation in porosity (0.2%~25.9%), with an average size of 12.5±3.0 nm, and good sorting is conducive to shale reservoir reconstruction after migration. Pore structure is mainly dominated by tiny pores, but due to larger specific surface area and strong methane adsorption ability, a large amount of methane adsorbed on the shale surface. According to contrast with the shale constituency parameters of American 5 basins, we suggest that Yongshun-Sangzhi and Cili-Shimen Area are favorable shale gas accumulation zones.

Bai D.,Hunan Institute of Geology Survey | Bai D.,Wuhan University | Li C.,Wuhan University | Zhang W.,Chinese Academy of Geological Sciences | And 2 more authors.
Scientia Geologica Sinica | Year: 2010

Lianghucun ZKC1 borehole is located in southeastern Anxiang sag of Dongting Basin. Quaternary sediments(including bottom Pliocene deposits)with thickness of 294 m in the borehole are composed of alluvial and lacustrine deposits, and were composed of Pliocene-Early Pleistocene Huatian Formation, Early Pleistocene Miluo Formation, Middle Pleistocene Dongtinghu Formation, Late Pleistocene Potou Formation and Holocene deposits. Detailed sporopollen analysis on the Quaternary deposits from ZKC1 borehole was conducted and 16 sporopollen-zones were identified. ESR age, sporopollen assemblages and corresponding climatic feature indicate that the lower part of Huatian Formation was formed at the end of Pliocene. According to the features of sporopollen assemblages and combined with tectonic-sedimentary evolution and regional climatic settings, the climatic evolution of Dongting Basin since the end of Pliocene was revealed as follows:Sporopollen-zone I and II indicate that the climate at the end of Pliocene was tropical and dry. From early to late, The climatic variations during Early Pleistocene are cool and dry(sporopollen-zone III and IV), tropical and humid interposed with cool and dry(sporopollen-zone V~VII), cold and dry interposed with warm and humid(sporopollen-zone VIII~X), tropic and weakly humid(sporopollen-zone XI and XIII). During Early Middle Pleistocene with no sporopollen sample the climate was cold and dry, which is suggested by sedimentary environment of gravels from lower part of Dongtinghu Formation; during middle Middle Pleistocene the climate was tropical and weakly humid which is indicated by sporopollen-zone XIII; during late Middle Pleistocene with no deposits formed for rise, the climate was tropical and humid which is indicated by tropical-humid event. According to regional climatic feature, the climate was dry in early Late Pleistocene with no deposits formed; during middle Late Pleistocene the climate was warm and weak humid which is indicated by sporopollen-zone XIV; there were no deposits formed for cold climate and sea-level dropped. From early to late, The climatic variations during Holocene are tropical and weak humid(sporopollen-zone XV), and tropical and weak dry(sporopollen-zone XVI). This climatic evolution process coincide basically with climatic change indicated by CIA(chemical index of alteration), and with Quaternary climatic variations of eastern China. There exist a sporopollen boundary at depth of 140 m over which there were more pollen and spore then under. This variation was in all probability related with an important geological event, and the cause of formation await embedded research in future.

Bai D.,Hunan Institute of Geology Survey | Bai D.,Wuhan University | Li C.,Wuhan University | Wang X.,Hunan Institute of Geology Survey | And 5 more authors.
Scientia Geologica Sinica | Year: 2010

Quaternary Huarong uplift is lacated at the center of Jianghan-Dongting Basin. Detail geologic mapping and bore data was taken to study on the landforms, Quaternary faults and deposits of Huarong uplift and its adjacent areas, and then to reveal the tectonic risesubsidenece characteristics and process. On the base of above progresses, the authors discussed the genesis and tectonic movement dynamic mechanisms of Huarong uplift. During Early Pleistocene-middle Middle Pleistocene Huarong uplift and its peripheral sags subsided together while the uplift controlled by several peripheral normal faults rose related to the sags. The uplift and the sags rose side by side in late Middle Pleistocene,and stabilize or subsided weakly during Late Pleistocene-Holocene. Huarong uplift took on obvious subsidence as a whole in 1uaternary. All above indicated that Huarong uplift was caused mainly by pre-Quaternary basin-mountain landforms, and secondly by the rise of the uplift related with peripheral sags. Geological characteristics of Huarong uplift and its periphery and regional geology references suggest that Jianghan-Dongting Basin was a faulted basin during Early Pleistocene-late Middle Pleistocene, and a depressional basin during late Middle Pleistoncene-Holocene. The authors discussed and bring forward modes about the dynamic mechanisms of Quaternary tectonic activities of Huarong uplift; 1 ) The faulted-subsidence of Jianghan-Dongting Basin during Early Pleistocene-middle Middle Pleistocene were related with the movemnet of deep matter to outside under the uplifting of mantle. 2 ) The tectonic activities since late Middle Pleistocene were possibly related with return of the earlier transported matter, plate-scale matter movement and compression. 3 ) Unitary subsidence of Jianghan-Dongting Basin made Huarong uplift at center of the basin subsided in the mass; on the other hand, special crust structure of Huarong uplift increased the difficulty of deep matter's movement, which caused Huarong uplift rise related to peripheral sags.

Bai D.,Hunan Institute of Geology Survey | Zhong X.,Hunan Institute of Geology Survey | Jia P.,Hunan Institute of Geology Survey | Xiong X.,Hunan Institute of Geology Survey
Geotectonica et Metallogenia | Year: 2014

There exist different views about the deformation of the Xuefeng Orogenic Belt. The authors studied the uncomformity, deformation timing and strength, geometrical and kinematic properties, dynamic mechanisms and tectonic regimes in the southern Xuefeng Orogenic Belt through profile measurements and regional geological survey, and reached the conclusions as follows: (1) There occurred main deformation types such as slaty cleavages, folds, thrusts, normal faults, sinistral and dextral strike-slip faults. (2) There existed notable compressional deformations with NW to NWW compression and NE to NNE-trending folds and thrusts in both the Caledonian event and Early Mesozoic tectonic events (Indosinian event and Early Yanshanian event). Slaty cleavages were formed in the Caledonian event. (3) Southern segment of the Xuefeng Orogenic Belt can be divided into the east and west zones by the Xupu-Jingzhou Fault, and they were the root and middle zone of the Xuefeng thrust system respectively. The deformation in the east was stronger than that of the west zone in the Caledonian event, as shown by slaty cleavages and tight folds in the east zone, whereas the west zone lacks slaty cleavage and with more open folds. Differences of layer dip angles, uncomformity, uplift, and rotation of former lineaments indicated that there existed stronger deformation in the east than west zones in Early Mesozoic tectonic events. (4) Dip directions of slaty cleavages, fold axial surfaces and thrusts indicated that there existed back thrusts in both Caledonian event and Early Mesozoic tectonic events in the east zone of the Xuefeng Orogenic Belt, however, the axis of the back thrust in the Early Mesozoic shifted about 20 km westwards. (5) The eastern segment of the Xupu-Jingzhou Fault turned into the root of the Xuefeng thrust system, which was related to its lower strength and it was a deep fault during early Nanhuan.

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