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Physical Modeling of fold-and-thrust belt Evolution and Triangle Zone Development:Dabashan Foreland belt(Northeast Sichuan basin,China) as an Example

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Acta Geologica Sinica(English Edition) 2013年第1期87卷 59-72页

作者： WANG Ruirui ZHANG Yueqiao XIE Guoai State Key Laboratory of Continental Tectonics and Dynamics Institute of GeologyChinese Academy of Geological Sciences Institute of Geomechanics Chinese Academy of Geological Sciences School of Earth Sciences and Engineering Nanjing University

Triangle zones, generally found in foreland fold-and-thrust belts, serve as favorable objects of petroleum exploration. Taking the Dabashan foreland belt as an example, we studied the formation and development of triangle zones, and investigated the effect of d^collements and the mechanical contrast of lithology by employing the method of physical modeling. Four experimental models were conducted in the work. The results showed that ＇sand wedges＇ grew episodically, recorded by deformational length, height and slope angle. The height versus shortening rate presented an S-shape curve, and uplifting occurred successively in the direction of the foreland belt. During the formation of the triangle zone, layer-parallel shortening took place at the outset; deformation decoupling then occurred between the upper and lower brittle layers, divided by a middle-embedded silicone polymers layer. The upper brittle layers deformed mainly by folding, while the lower sand layers by thrusting. As shortening continued, the geometry of a triangle zone was altered. We consider that the triangle zone in the Dabashan foreland belt was modified from an early one based on available seismic profiles and the experimental results. In addition, dccollements and mechanical contrast impose significant influence on structural development, which can directly give rise to structural discrepancies. More d^collements and obvious mechanical contrast between brittle layers can promote the coupling between the upper and lower brittle layers. Basal d^collement controls the whole deformation and decreases the slope angle of the wedge, while roof d^collement determines whether a triangle zone can be formed.

关键词： physical modeling Dabashan fold-and-thrust belt triangle zone decollement mechanicalcontrast of lithology

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Cohesive Strength and Seismogenic Stress Pattern along the Active Basement Faults of the Precordillera-Sierras Pampeanas Ranges,Western Argentina:An Experimental Analysis by Means of Numerical Model

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Journal of Mountain Science 2009年第4期6卷 331-345页

作者： Md. Rafiqul Islam Department of Physics and Earth Sciences Faculty of ScienceUniversity of the Ryukyus

A two-dimensional finite element method （FEM） model that incorporates faults, elastic rock physical properties, topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize the seismogenic stress state along the fold-and-thrust belt of the Precordillera-Sierras Pampeanas ranges of western Argentina. A plane strain model with nine experiments was presented here to examine the fault strength with two major rock phyical properties： cohesion and angle of internal friction. Mohr-Coulomb failure criterion with bulk rock properties were applied to analyse faults. The stress field at any point of the model was assumed to be comprised of gravitational and tectonic components. The analysis was focused to recognize the seismogenic shear strain concentrated in the internal-cristaline domain of the orogene shown by the modeling. Modeling results are presented in terms of four parameters, i. e., （i） distributions, orientations, and magnitudes of principal stresses （σ1 and σ3）, （ii） displacement vector1 （iii） strain distribution, and （iv） maximum shear stress （τmax） contour line within the model. The simulation results show that the compressive stress is distributed in and around the fault systems. The overall orientation of of σ1 is in horizontal directions, although reorientations do occur within some stress weaker parts, especially subsequent to the faults. A large-scale shear stress is accumulating along the active faults of Tapias-Villicum Fault （TVF）, Salinas-Berros Fault （SBF）, Ampacama-Niquizanga Fault （ANF） and Las Charas Fault （CF）, which could act as local stress and strain modulators to localize the earthquakesoccurrence.

关键词： Finite element method Rock physical property fold-and-thrust belt Fault strength Seismogenic shear stress pattern

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Deformation geometry and timing of the Wupoer thrust belt in the NE Pamir and its tectonic implications

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Frontiers of Earth Science 2016年第4期10卷 751-760页

作者： Xiaogan CHENG Hanlin CHEN Xiubin LIN Shufeng YANG Shenqiang CHEN Fenfen ZHANG Kang LI Zelin LIU School of Earth Sciences Zhejiang University Hangzhou 310027 China Research Center for Structures in Oil- and Gas-Bearing Basins Ministry of Education Hangzhou 310027 China Department of Exploration Geophysics College of Geophysics and Information Engineering China University of Petroleurn-Beijing Beijing 102249 China

The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion geometry and timing of the Wupoer thrust belt at the northeastem margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene （N2） and the underlying Miocene （NI） or Paleogene （Pg） strata associated with two other local unconformities between Lower Pleistocene （Q1） and N2 and between Middle Pleistocene （Q2-4） and Q1 strata. Results of structural restorations suggest that compres- sional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, com- bined with previous studies on the Kongur and Tarshkor- gan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concur- rent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a decollement along which both the extensional and compressional faults merged.

关键词： Pamir Kongur Wupoer gravitational collapse fold-and-thrust belt

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Crustal Electrical Structure of the Wuwei Basin,Lower Yangtze Region of China,and Its Geological Implications

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Journal of Earth Science 2023年第6期34卷 1744-1757页

作者： Xiaobo Zhang Penghui Zhang Meixing He Dashuang He Fagen Pei Yaoyang Zhang Yan Peng Institute of Geophysical and Geochemical Exploration Chinese Academy of Geological SciencesLangfang 065000China National Research Center for Geo-exploration Technology Langfang 065000China College of Earth Sciences Chengdu University of TechnologyChengdu 610059China

The Wuwei Basin is one of the most important oil-and gas-bearing basins in the Meso-Cenozoic basin groups in the Lower Yangtze River *** has great shale gas resource *** formation mechanism of this basin is poorly studied for lack of constraining data for deep *** this paper,a crustal electrical structure model of the Wuwei Basin and the adjacent areas is constructed based on the two-dimensional inversion of a magnetotelluric(MT)sounding profile achieved with the nonlinear conjugate gradient *** results show that large-scale low-resistance bodies have developed in the underlying middle and lower crust of the Wuwei Basin,and are different from the uplifts on the two sides according to their high-resistance electrical *** electrical structure and regional geological and geophysical data suggest that the peak zone of the Chuzhou-Chaohu foreland fold-and-thrust belt is located on the east bank of the Yangtze River(Wuhu Section),which,together with the main thrust fault belt in the east,forms a typical thrust structure *** early Yanshanian sinistral strike-slip fault developed in the deep part of the Wuwei Basin,which may have controlled the formation and evolution of the basin,whereas the tectonic inversion of the early-developed thrust faults is relatively *** findings provide a geophysical basis for future studies of basin tectonic evolution and regional tectonic frameworks.

关键词： Wuwei Basin Lower Yangtze deep structure electrical structure fold-and-thrust belt shale gas magnetotellurics geophysics

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Early Mesozoic tectonics of the South China block:Insights from the Xuefengshan intracontinental orogen

Early Mesozoic tectonics of the South China block:Insights f...

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中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： Yang Chu Michel Faure Wei Lin Qingchen Wang State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Institut des Sciences de la Terre d'Orleans Campus GeosciencesUniversite d'Orleans

Intracontinental orogens remain less understood than accretionary or collisional orogens that are related to plate margin *** the center of the South China block,the Xuefengshan belt provides a well-exposed example of such an intracontinental orogen of Early Mesozoic *** field tectonic observations indicate that the Xuefengshan belt can be divided into a Western Outer Zone characterized by km-scale box-fold structures,and an Eastern Zone,separated from the Western Outer Zone by the SE-dipping Main Xuefengshan *** the Eastern Zone,NW verging folds coeval with a pervasive slaty cleavage and a NW-SE trending lineation are the dominant *** west to east,the dip of the cleavage surface exhibits a fan-like *** bulk architecture of the Xuefengshan belt results from polyphase deformation:D is characterized by a top-to-the-NW ductile shearing;D corresponds to SE-directed back thrusting and folding;D consists of upright folds with vertical cleavage and lineation. At depth,a high strain zone characterized by greenschist facies metamorphic rocks and a top-to-the-NW ductile shearing corresponds to a ductile decollement zone that accommodated the deformation of the Neoproterozoic to Early Triassic sedimentary *** compatibility suggests that the synmetamorphic ductile shearing was coeval with the D event in the sedimentary *** Xuefengshan belt is interpreted as an Early Mesozoic intracontinental orogen,which possibly originated from the SE-directed continental subduction of a piece of the South China block in response to northwestwards subduction of the Pacific plate.

关键词： Intracontinental orogen fold-and-thrust belt Xuefengshan belt South China block Early Mcsozoic orogeny

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