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Early Cenozoic Tectonics of the Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2013年第2期87卷 289-303页

作者： WU Zhenhan hu daogong YE Peisheng WU Zhonghai Chinese Academy of Geological Sciences Institute of Geomechanics Chinese Academy of Geological Sciences

Geological mapping at a scale of 1：250000 coupled with related researches in recent years reveal well Early Cenozoic paleo-tectonic evolution of the Tibetan Plateau. Marine deposits and foraminifera assemblages indicate that the Tethys-Himalaya Ocean and the Southwest Tarim Sea existed in the south and north of the Tibetan Plateau, respectively, in Paleocene-Eocene. The paleo- oceanic plate between the Indian continental plate and the Lhasa block had been as wide as 900km at beginning of the Cenozoic Era. Late Paleocene transgressions of the paleo-sea led to the formation of paleo-bays in the southern Lhasa block. Northward subduction of the Tethys-Himalaya Oceanic Plate caused magma emplacement and volcanic eruptions of the Linzizong Group in 64.5-44.3 Ma, which formed the Paleocene-Eocene Gangdise Magmatic Arc in the north of Yalung-Zangbu Suture （YZS）, accompanied by intensive thrust in the Lhasa, Qiangtang, Hoh Xil and Kunlun blocks. The Paleocene- Eocene depression of basins reached to a depth of 3500-4800 m along major thrust faults and 680-850 m along the boundary normal faults in central Tibetan Plateau, and the Paleocene-Eocene depression of the Tarim and Qaidam basins without evident contractions were only as deep as 300-580 m and 600-830 m, respectively, far away from central Tibetan Plateau. Low elevation plains formed in the southern continental margin of the Tethy-Himalaya Ocean, the central Tibet and the Tarim basin in Paleocene-Early Eocene. The Tibetan Plateau and Himalaya Mts. mainly uplifted after the Indian- Eurasian continental collision in Early-Middle Eocene.

关键词： paleo-tectonics paleo-elevation subduction of the oceanic plate Paleocene-Eocene theTibetan Plateau

Zircon SHRIMP U-Pb Dating, Geochemical Characteristics and Tectonic Significance of Granitic Gneisses in Amdo, Tibet

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Journal of Earth Science 2014年第3期25卷 473-485页

作者： Lu Lu Zhenhan Wu Zhen Zhao daogong hu Peisheng Ye Chinese Academy of Geological Sciences Institute of Geomechanics Chinese Academy of Geological Sciences

The Amdo microcontinent is located within the middle of Bangong-Nujiang suture（BNS） zone in the shape of lens. The basic geological research restricts geologists from understanding the histories of tectonic evolution of BNS and regional geology more deeply. This paper systematically studies the geochronology and geochemistry of granitic gneisses from Amdo basement. These data provide constraints on formation age, source characteristics and tectonic setting of their protolith. The SHRIMP zircon U-Pb dating is operated for granitic gneisses. Samples AGS-2 and AGS-3（granitic gneiss） yield average zircon U-Pb ages of 485±14 and 487±6 Ma, respectively. These ages should represent the formation age of protolith and indicate that they are formed in the Early Ordovician. Granitic gneisses are characterized by high SiO2, Na2O, K2O and Al2O3, low Fe and Mg, enrichment in light rare earth elements（LREEs） and large ion lithophile elements（LILEs）, depletion in heavy rare earth elements（HREEs） and high field strength elements（HFSEs）, with negative Eu anomaly. The Rittmann index（σ） is 1.77 to 2.60, less than 3.3. The aluminum saturation index（A/CNK） values range from 0.88 to 1.26. These features suggest that protolith of granitic gneisses from Amdo basement show characteristics of calc-alkaline and S-type granite, and they could be derived from partial melting of metamorphic greywackes in the upper crust of low maturity. The tectonic setting is syn-collision. These all suggest that the formation of protolith of granitic gneisses from Amdo are caused by the Early Paleozoic orogeny, which could be related to proto-Tethyan oceanic subduction along Gondwana continental margins, and does not result from the production of Pan-African orogenesis.

关键词： granitic gneiss zircon U-Pb age geochemical Amdo Tibet.

Late Quaternary normal faulting and its kinematic mechanism of eastern piedmont fault of the Haba-Yulong Snow Mountains in northwestern Yunnan, China

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Science China Earth Sciences 2009年第10期52卷 1470-1484页

作者： WU ZhongHai ZHANG YongShuang hu daogong ZHAO XiTao YE PeiSheng Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

The regional geologic and geomorphic observations show that an active arcuate normal fault constitutes the main boundary fault of the Haba-Yulong Snow Mountains (HYSM). This fault is called eastern piedmont fault of Haba-Yulong Snow Mountains (HYPF). The fault consists of two segments with differential trend; the northern segment is NW-trending and NE-dipping and the southern section is S-N trending and E-dipping. Three sets of fault scarps cutting late Quaternary landforms and their dating results indicate that the fault is a prominent Holocene active fault and its throw rates are 0.3―1.4 mm/a during late Quaternary. The geometry and kinematics of the fault suggest that the arcuate normal faulting or rifting are typical surface deformation pattern at the two tips of the Z-shaped rift zone of northwestern Yunnan, which is related to regional east-west extension accompanying clockwise rota- tion of micro-block.

关键词： northwestern Yunnan the Haba-Yulong Snow Mountains Quaternary normal faulting blocks rotation

Quantitative Zoning Assessment of Crustal Stability Along the Yunnan-Tibet Railway Line,Western China

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Acta Geologica Sinica(English Edition) 2012年第4期86卷 1004-1012页

作者： ZHANG Yongshuang YAO Xin hu daogong GUO Changbao XIONG Tanyu Key Laboratory of Neotectonic Movement and Geohazard Ministry of Land and Resources Institute of Geomechanics Chinese Academy of Geological Sciences

The planned Yunnan-Tibet railway goes through the northwest of Yunnan Province and the southeast of the Tibet Autonomous Region. Because of its location near the collision belt of the Eurasian and Indian plates, complex engineering geological conditions and difficult engineering geological problems are encountered. The study is aimed at making the zoning assessment of crustal stability along the railway line so as to provide a better base for its construction, especially its line selection. For this purpose, the following seven influencing factors of crustal stability were selected and quantified by grading and scoring： active fault, seismic activity, geo-stress field, geo-strain field, geothermal field, geo-hazard, and lithologic character. Of these factors, the active fault, seismic activity and geo-hazard are the three most prominent factors influencing the railway construction. Along the railway line there are 1731703 calculation units to be divided. The zoning assessment calculation was completed by ArcGIS-based information fusion method. The assessment results aid railway line selection and show that there are 10 stable sectors, 28 relatively stable sectors, 23 relatively unstable sectors, and 20 unstable sectors along the Yunnan-Tibet railway line.

关键词： railway engineering geo-hazard active fault crustal stability influence factor zoning assessment Yunnan province Tibet

The variety of thermal conduction resulting from segmented degree of heat source body and its bearing on temperature change

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Chinese Science Bulletin 1999年第15期44卷 1411-1415页

作者： Guxian Lü Hongcai Wang Tao Guo Yinsheng Ma daogong hu Chinese Acad Geol Sci Inst Geomech Beijing 100081 Peoples R China

The differences of thermal conduction and its temperature-varying track of the heat source body at various structural environments have been studied. Hypothetically, geologic heat source body is cut successively into several segregative bodies with a fixed cubage. With the segmented number increasing, the conductive surface area of heat source body begins to get larger, which separately is similar to the heat geologic body in different tectonic zones that has a various enclosed coefficient η（η=S0/sum from i=（1,n）（Si））. Finite-element simulation result shows that the thermal conduction speed of spreading from the heat source body to its wall rock is slow→higher→highest, when heat source bodies are situated respectively at compressive, shear and tensile deformation zones, corresponding rates of their temperature drop are low→higher→highest. Research indicates that the temperature’s dropping rate of heat source body has an inverse relationship with enclosed coefficient η for different structural

关键词： thermal conduction segmented degree finite-element tectono-physicochemistry.

Early Cenozoic Mega Thrusting in the Qiangtang Block of the Northern Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2012年第4期86卷 799-809页

作者： WU Zhenhan YE Peisheng Patrick J.BAROSH hu daogong LU Lu ZHANG Yaoling Chinese Academy of Geological Sciences Institute of Geomechanics Chinese Academy of Geological Sciences P.J.Barosh and Associates 103 Aaron Ave.BristolRI 02809USA

Recent mapping and seismic survey reveal that intensive compression during the Early Cenozoic in the Qiangtang block of the central Tibetan Plateau formed an extensive complex of thrust sheets that moved relatively southward along several generally north-dipping great thrust systems. Those at the borders of the ~450 km wide block show it overrides the Lhasa block to the south and is overridden by the Hohxil-Bayanhar block to the north. The systems are mostly thin-skinned imbricate thrusts with associated folding. The thrust sheets are chiefly floored by Jurassic limestone that apparently slid over Triassic sandstone and shale, which is locally included, and ramped upward and over Paleocene-Eocene red-beds. Some central thrusts scooped deeper and carried up Paleozoic metamorphic rock, Permian carbonate and granite to form a central uplift that divides the Qiangtang block into two parts. These systems and their associated structures are unconformably overlain by little deformed Late Eocene-Oligocene volcanic rock or capped by Miocene lake beds. A thrust system in the northern part of the block, as well as one in the northern part of the adjacent Lhasa block, dip to the south and appear to be due to secondary adjustments within the thrust sheets. The relative southward displacement across this Early Cenozoic mega thrust system is in excess of 150 km in the Qiangtang block, and the average southward slip-rate of the southern Qiangtang thrusts ranged from 5.6 mm to 7.4 mm/a during the Late Eocene-Oligocene. This Early Cenozoic thrusting ended before the Early Miocene and was followed by Late Cenozoic crustal extension and strike-slip faulting within the Qiangtang block. The revelation and understanding of these thrust systems are very important for the evaluation of the petroleum resources of the region.

关键词： mega thrust outliers and thrust sheets structural windows Early Cenozoic Qiangtang block Northern Tibetan Plateau

Seismogenic Structure of the 1605 Qiongshan M7½ Earthquake and Its Holocene Activity History in Northern Hainan Island, China: Evidence from Cross-Section Drilling and Shallow Seismic Profile

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Journal of Earth Science 2024年第3期35卷 905-917页

作者： Chaoqun Wang Liyun Jia daogong hu Shibiao Bai Zhengwang hu Dongxia Sun Xiaoxiao Yang Lei Zhang Xiumin Ma Institute of Geomechanics Chinese Academy of Geological SciencesBeijing 100081China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesBeijing 100081China Key Laboratory of Geohazard Prevention of Hilly Mountains Ministry of Land and Resources(Fujian Key Laboratory of Geohazard Prevention)Fuzhou 350002China Observation and Research Station of Crustal Stress and Strain in Beijing Ministry of Natural ResourcesBeijing 100081China College of Marine Science and Engineering Nanjing Normal UniversityNanjing 210023China hubei Subsurface Multi-Scale Imaging Key Laboratory School of Geophysics and GeomaticsChina University of GeosciencesWuhan 430074China

The 1605 M7½ Earthquake is the only earthquake in the history of China that has caused large-scale land subsidence into the sea,with the total area of land subsidence exceeding 100 *** disaster has led to the sinking of 72 *** is still no clear understanding of the source seismogenic fault of this *** this work,we conducted a detailed study of the middle segment of the Maniao-Puqian fault(MPF),which is the epicenter area,through geomorphological survey,data collection,shallow seismic exploration,cross-section drilling,and chronological *** results showed that the middle segment of the MPF zone is composed of three nearly parallel normal faults with a dextral strike-slip:“Macun-Luodou fault(F2-1),Haixiu-Dongyuan fault(F2-2),and ChangliuZhuxihe fault(F2-3)”.And F2-2 is composed of two secondary faults,namely F2-2′and F2-2″,with a flower-shaped structure buried under the *** is distributed nearly east-west,dipping to the north and has experienced at least five stages of activities since the *** vertical activity rates of F2-2′and F2-2″are~2.32 and~2.5 mm/a,since the Holocene,*** were eight cycles of transgression and regression since the *** fault activity resulted in the thickening of the Holocene strata with a slight dip to the south,on the hanging wall,showing V-shaped *** MPF is likely the source seismogenic fault of the M7½ earthquake that hit Qiongshan in 1605.

关键词： seismogenic structure earthquakes Maniao-Puqian fault fault activity history geomorphology.

Miocene Tectonic Evolution from Dextral-Slip Thrusting to Extension in the Nyainqentanglha Region of the Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2007年第3期81卷 365-384页

作者： WU Zhenhan Patrick J. BAROSH ZHAO Xun WU Zhonghai hu daogong LIU Qisheng Institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China P. J. Barosh 103 Aaron Avenue Bristol RI 02809 USA Chinese Academy of Geological Sciences Beijing 100037 China

Dextral-slip in the Nyainqentanglha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the northeast-trending, southeast-dipping Nyainqentanglha thrust system that swings eastward farther north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqentanglha granitic batholith formed along the thrust system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at -11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Lhtinzhub thrust faults with dextral-slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at -6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, DamxungYangbajain and Angan graben systems that pass east of the Nyainqentanglha Mountains are locally controlled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.

关键词： Miocene tectonics strike-slip fault thrust fault extensional tectonic system uplift graniteplutonism Nyainqentanglha region Tibetan Plateau

Rapid Identification and Emergency Investigation of Surface Ruptures and Geohazards Induced by the M_s 7.1 Yushu Earthquake

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Acta Geologica Sinica(English Edition) 2010年第6期84卷 1315-1327页

作者： ZHANG Yongshuang YAO Xin XIONG Tanyu MA Yinsheng hu daogong YANG Nong GUO Changbao Key Laboratory of Neotectonic Movement and Geohazard MLR Beo＇ing 100081 China Institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China

The rapid identification based on InSAR technology was proved to be effective in our emergency investigation of surface ruptures and geohazards induced by the Yushu *** earthquake-generating fault of the Yushu earthquake is the Yushu section of the Garze-Yushu faults *** strikes NWW-NW,23 km long near the Yushu County seat,dominated by left-lateral strike slip,and appearing as a surface rupture *** macroscopic epicenter is positioned at Guo-yang-yan -song-duo of Gyegu Town（33°03＇11＂N,96°51＇26＂E）,where the co-seismic horizontal offset measured is 1.75 *** induced by the Yushu earthquake are mainly rockfalls,landslides,debris flows, and unstable *** are controlled by the earthquake-generating fault and are mostly distributed along *** are several geohazard chains having been established,such as earthquake,canal damage,soil liquefying,landslide-debris flow,earthquake,soil liquefying,roadbed deformation,*** order to prevent seismic hazards,generally,where there is a visible surface rupture induced by the Yushu earthquake,reconstruction should be at least beyond 20 m,on each side,from *** attention should also be given to potential geohazards or geohazard chains induced by the earthquake.

关键词： Yushu earthquake InSAR surface rupture macroscopic epicenter earthquake geohazard