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Anatexis in Himalayan crust:Evidence from geochemical and chronological investigations of Higher Himalayan Crystallines

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Science china Earth Sciences 2005年第9期48卷 1347-1356页

作者： YANG Xiaosong1, JIN Zhenmin2.& MA Jin1 1. State Key laboratory of Earthquake Dynamics, Institute of Geology, china Earthquake Administration, Beijing 10002., china 2. Faculty of Earth Sciences, china University of Geosciences, Wuhan 4.0074. china 1. State Key laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration 100029 Beijing China 2. Faculty of Earth Sciences China University of Geosciences 430074 Wuhan China

Migmatization in Higher Himalayan Crystallines (HHC) results from anatexis. The widely distributed migmatites in HHC are an important clue to investigate the relationship be- tween anatexis and the origins of Higher Himalayan leucogranites (HHL), and to understand the effect of anatexis on crustal evolution during the post-collision period. We studied in detail the chemical features of three basic constituent parts of the migmatites, i.e. leucosome, mesosome and melanosome, and determined the K-Ar ages of leucosomes. Our studies indicate that type-I leucosome is the product of crystallization of melt generated by partial melting of mesosome at source region, but type-II leucosome and HHL probably underwent crystallization differentiation of plagioclase during melt aggregation and migration. The age of 2..67 Ma of Type-I leucosome, which is a little older than the beginning of MCT movement, indicates that anatexis may have played an important role in the formation of MCT. That the ages of type-II leucosome (ranging from 14.82.to 18.37 Ma) are consistent with that of HHL provides new chronological evidence for the relationship between migmatization and HHL. We obtained a very young age of 6.2. Ma of Type-II leucosome that provides new time constraint on magma activity in the central segment of Higher Himalayas.

关键词： Higher Himalayan Crystallines, migmatite, anatexis, leucosome, K-Ar age.

The history of crustal uplift and metamorphic evolution of Panzhihua-Xichang micro-palaeoland, SW china:Constraints on Sm-Nd, ^(4.)Ar/^(39)Ar and FT ages of granulites

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Science china Earth Sciences 2004年第8期47卷 689-703页

作者： XU Shijin1, LIU Wenzhong1, WANG Rucheng1, YU Hangbo1, LI Daming2. WAN Jinglin2.& FANG Zhong1 1. Department of Earth Sciences and State Key laboratory for Mineral Deposits Research, Nanjing University, Nanjing 2.0093,{4. 2. Institute of Geology,{4. Seismological Bureau, Beijing 10002.,{4. 1. Department of Earth Sciences and State Key laboratory for Mineral Deposits Research Nanjing University 210093 Nanjing China 2. Institute of Geology China Seismological Bureau 100029 Beijing China

Panzhihua-Xichang (Panxi) micro-palaeoland is the oldest terrane on the western margin of the Yangtze Block. Some intermediate-basic granulites are considered to be the crys-talline basement of lower crust in the terrane. Granulite-facies metamorphism of the granulites was developed in the period from 1186 Ma to 112. Ma. The origin of granulites was related to the collision orogenic process occurring when the micro-palaeolands merged to form the Rodinia Supercontinent. Amphibolite-facies retrogressive metamorphism of granulites took place in the period from 877 Ma to 82. Ma. This period was consistent with the breakup time of the Rodinia Supercontinent. 4.Ar/39Ar ages and fission track (FT) ages of granulites in the Panxi mi-cro-palaeoland show that the vertical movement history of crustal rocks was a slow uplift process of the rigid terrane in the time from Neoproterozoic to Mesozoic. The subduction of India Plate towards Euroasia Plate resulted in the rapid uplift of the Qinghai-Tibetan Block in Cenozoic. Meanwhile, the Qinghai-Tibetan Block moved towards east. Consequently the Panxi terrane was uplifted rapidly. As a result of the collision orogeny between the Qinghai-Tibetan Block and the Panxi terrane, the granulite-facies crystalline basement in this region was exhumed and exposed to the surface.

关键词： granulite,isotope geochronology,crustal uplift movement,Panzhihua-Xichang region,western margin of Yangtze Block.

Dynamic mechanisms of the post-seismic deformation following large events:Case study of the 1999 Chi-Chi earthquake in Taiwan of china

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Science china Earth Sciences 2009年第11期52卷 1813-1824页

作者： ZHU ShouBiao1,2.& CAI YongEn2.1 Institute of crustal Dynamics, china Earthquake Administration, Beijing 100085, china 2.Department of Geophysics, Peking University, Beijing 100871, china 1. Institute of crustal Dynamics China Earthquake Administration Beijing 100085 China 2. Department of Geophysics Peking University Beijing 100871 China

The mechanism of postseismic deformation related to strong earthquakes is important in geodynamics, and presumably afterslip or viscoelastic relaxation is responsible for the postsesimic deformation. The 1999 Chi-Chi, Taiwan of china, earthquake occurred in the region where GPS observation station is most densely deployed in the world. The unprecedented GPS data provides a unique opportunity to study the physical processes of postseismic deformation. Here we assume that the interactions of viscoelastic relaxation, afterslip, fault zone collapse, poroelastic rebound, flow of underground fluids, and all these combined contribute to the surface displacements following the main shock. In order to know the essence of the postseismic deformation after the strong event, fault zone collapse, poroelastic rebound, flow of underground fluids, and so on, are represented equivalently by the variations of the focal medium properties. Therefore, the viscoelastic relaxation, afterslip, and the variations of the equivalent focal medium properties are inverted by applying the GPS temporal series measurement data with viscoelastic finite element method. Both the afterslip rate distribution along the fault and the afterslip evolution with time are obtained by means of inversion. Also, the preliminary result suggests that viscosities of the lower crust and the upper mantle in Taiwan region is 2.7×1018 and 4.2.102. Pa·s, respectively. Moreover, the inversion results indicate that the afterslip contributing to postseismic deformation of 4..6% in 4.0 days after the Chi-Chi earthquake, with 34.7% caused by the viscous relaxation and 2..7% by other factors such as fault zone collapse, poroelastic rebound, and the flow of liquids.

关键词： mechanism of postseismic deformation viscoelastic finite element method GPS temporal series data Chi-Chi earthquake

Dislocation structure of the crust-mantle boundary and low-velocity body within the crust beneath the Dabie Shan collision orogen

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Science china Earth Sciences 2005年第7期48卷 875-885页

作者： LIU Qiyuan1, Rainer Kind2. CHEN Jiuhui1, YUAN Xiaohui2. LI Shuncheng1, GUO Biao1, Kurt Wylegalla2.& LAI Yuangen1 1. State Key laboratory of Earthquake Dynamics, Institute of Geology,{4. Earthquake Administration, Beijing 10002.,{4. 2. GeoForschungZentrum Potsdam, Telegrafenburg A17, Potsdam, D-14.73, Germany State Key laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing 100029 China GeoForschungZentrum Potsdam Telegrafenburg A17 Potsdam D-14473 Germany

From April of 2.01 to March of 2.02. a passive seismic array experiment was car- ried out in the Dabie Shan and its adjacent region. In this experiment, totally 34.broadband seismic stations were deployed along a profile across the Dabie Shan orogen and North-china platform. This profile is about 500 km long from Cuilin (34.4.′N, 114.4.′E), Henan Province, to Dajipu (30°2.′N, 115°03′E), Hubei Province. The space between stations is about 3?8 km in the Dabie Shan orogenic belt and about 15?2. km in other area. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km depth along the profile are investigated in terms of the receiver function techniques (Liu et al., 1996, 2.00). Our results show that the crust beneath the Dabie Shan orogen has an obviously asymmetric blocked structure in the direction perpendicular to the mountain strike. The maximal crustal thickness reaches to 4.0}km. The crust-mantle boundary has a dislocation structure correlated to the crustal blocks and the largest offset reaches to 8 km. In the kernel of the orogen exists a low-velocity body inside the crust, which is separated into two parts corresponding to the South Dabie and North Dabie on the surface, respectively. Probably a vertical divergent movement between both took place in history. The crust below this low-velocity area has a positive gradient velocity structure with the depth, and the upper mantle down to the depth of 70 km has the lower S-wave velocity than its both sides. Beneath the Dabie Shan, however, a high-velocity anomaly exists in the upper mantle below 70 km.

关键词： receiver function low-velocity body Moho discontinuity Dabei Shan collision orogen.

Lithosphere types in North china:Evidence from geology and geophysics

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Science china Earth Sciences 2005年第11期48卷 1809-1827页

作者： QIU Ruizhao1,2. DENG Jinfu3, ZHOU Su3, LI Jinfa4. XIAO Qinghui1,5, WU Zongxu6 & LIU Cui3 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, china 2. Development and Research Center, china Geological Survey, Beijing 100037, china 3. china University of Geosciences, Beijing 100083, china 4. china University of Geosciences, Wuhan 4.0074. china 5. Information Center of Ministry of Land and Resources, Beijing 100812. china 6. Institute of Geology, State Seismological Bureau, Beijing 10002., china 1. Institute of Geology Chinese Academy of Geological Sciences 100037 Beijing China 2. Development and Research Center China Geological Survey 100037 Beijing China 3. china University of Geosciences 100083 Beijing China 4. china University of Geosciences 430074 Wuhan China 5. Information Center of Ministry of Land and Resources 100812 Beijing China 6. Institute of Geology State Seismological Bureau 100029 Beijing China

On the basis of the characteristics of geology and geophysics in North china, three types of lithosphere, namely, the cratonic, the orogenic and the rift lithospheres can be classified. In terms of petrological method (based on the information from Precambrian rock assemblages, igneous activities, deep-seated enclaves, etc.) and the relationship between seismic velocity and rock compositions, the crust-mantle petrological and chemical structure models can be set up. Researching results indicate that the geology and geophysics of North china platform bears the similar characteristics in comparison with those of the global typical cratons. The Eerduosi(Ordos) block located in the west of the North china Platform is a remnant of cratonic lithosphere after the North china platform had undergone “activation” in Mesozoic and “reconstruction” in Cenozoic times. The continental crust consists mainly of TTG rock assemblage while the subcontinental lithosphere mantle mainly consists of strongly depleted harzburgite. The craton was finally formed in late Archaean and early Proterozoic, and has been kept in stability up to present; its {4.-mantle petrological structures of lithosphere can be set up as a reference for the study of North china craton and even Sino-Korean craton. In the Mesozoic period, the middle and east areas of North china platform were activated in the Yanshanian orogenic process, the continental crust was reformed by material and heat-transfer of convective mantle and the original {4. TTG component was reconstructed to be granitic crust, and the subcontinental lithosphere man- tle was replaced by the Yanshanian harzburgite-lherzolite. The Yanshan-Taihang Mountains were the remnants of orogenic lithosphere after the rifting in eastern North china in Cenozoic. The present thickness of continental crust and lithosphere in the Yanshan-Taihang Mountains is not equal to their thickness during the Yanshanian orogenic movement because they had undergone the

关键词： lithospheric types,evidence of geology and geophysics,crust-mantle petrological structure,deep process

Geomorphological effects of plate movement during Quaternary in china' s tropics

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Journal of Geographical Sciences 2004年第2期 124-129页

作者： ZHANG Weiqiang 1 ,HUANG Zhenguo 2.(1. Guangdong Business College, Guangzhou 51032., china 2. Guangzhou Institute of Geography, Guangzhou 510070, china)

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in china's tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and {4. deformation imply that the juncture zone of eastern and western tectonic forces is located at about 110 o E.

关键词： plate tectonic geomorphological effect china’s tropics

Discovery and analysis of ultra-micro grinding grain texture in slipping lamellae of ductile-brittle zone

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Science china Earth Sciences 2004年第3期47卷 265-271页

作者： GE Heping1, SUN Yan1, LU Xiancai1, ZHU Wenbin1, GUO Jichun1, LIU Deliang2.& Chi-yuen Wang3 1. Department of Earth Sciences, Nanjing University, State Key laboratory of Mineral Deposit, Nanjing 2.0093, china 2. Department of Earth and Space Sciences, University of Science and Technology of china, Hefei 2.002., china 3. Department of Geology and Geophysics, University of California, Berkeley, CA 94.2., USA Nanjing Univ Dept Earth Sci State Key Lab Mineral Deposit Nanjing 210093 Peoples R China Univ Sci & Technol china Dept Earth & Space Sci Hefei 230026 Peoples R China Univ Calif Berkeley Dept Geol & Geophys Berkeley CA 94720 USA

Based on the observation of the deep bore cores sampled from the State of Cali-fornia, USA, preferred arranged particulate concentration belts were found in the ultra-slipping lamellae. And the same phenomenon was found again later in the bore cores from the petroleum basin in the Northern Shaanxi Province. It may be the product of the dynamic processes involv-ing tumbling, grinding and compresso-shearing functions, so the spherical particulates with ul-tra-size of nm and mm are called grinding grain. The formation of the grinding grains is related with the ductile-brittle deformation, the lateral pressure of the slipping, and the very low grade of dynamic metamorphism of the rocks. Based on the systematic analysis, it is indicated that some elements like Nb and Ta are enriched in the grinding grains in the granitic rocks because of the chemical differentiation, and that the slipping lamellae bearing grinding grains in mudstone with smear efficiency prove a perfect seal for oil and gas reservoirs. Meanwhile, the paper provides bases for the studies on the fast stick-slip movement and shear paradigm.

关键词： slipping lamellae, grinding grain texture, ductile-brittle deformation, smear efficiency.

Gravity Changes Before Large Earthquakes in china: 1998-2.05

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地球空间信息科学学报（英文） 2011年第1期14卷 1-9页

作者： ZHAN F. Benjamin ZHU Yiqing NING Jinsheng ZHOU Jiangcun LIANG Weifeng XU Yunma School of Resource and Envirorunental Science Wuhan University 129 Luoyu Road Wuhan 430079 China Texas Center for Geographic Information Science Texas State University San Marcos TX 78666 USA Institute of Geodesy and Geophysics Chinese Academy of Sciences 340 Xudong Street Wuhan 430077 China Second Crust Monitoring and Application Center China Earthquake Administration Xi'An 710054 China School of Geodesy and Geomatics Wuhan University 129 Luoyu Road Wuhan 430079 China

Although it is well known that coseismic gravity changes take place during an earthquake, previous research has not yielded convincing evidence demonstrating that significant gravity changes occur before large earthquakes. Furthermore, even if we suspect that gravity changes occur before large earthquakes, we have yet to demonstrate how to consistently observe these changes for useful earthquake forecast that would bring benefits to society. We analyzed ground gravity survey data obtained in 1998, 2.00, 2.02. and 2.05 at stations of the {4. movement {2. Network of china (CMONOC) and examined gravity changes be-fore the occurrence of nine large (Ms≥6.8) earthquakes that ruptured within or near china's Mainland and Taiwan from November 2.01 to August 2.08. Results from this analysis show that significant gravity changes occurred across a large region before each of these nine large earthquakes, and these changes were detected by repeated ground gravity surveys through CMONOC. Although these gravity changes were significant, more research is needed to investigate whether these gravity changes could be viewed as precursors of large earthquakes. Limitations and uncertainties in the data include sparseness of the gravity monitoring network, long time intervals between consecutive gravity surveys, inevitable measurement errors, hydrological effects on gravity, and effects of vertical {4. movements on gravity. Based on these {2.s, we make several recommendations about possible future direc-tions in earthquake-related research using gravity monitoring data.

关键词： earthquake gravity seismology china Wenchuan geodesy GIS

The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations

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Science china Earth Sciences 2008年第8期51卷 1064-1080页

作者： YANG ShaoMin1,2. LI Jie1,3 & WANG Qi2.1 1 Research Center of Space Science and Technology, china University of Geosciences, Wuhan 4.0074. china 2.Institute of Seismology, china Earthquake Administration, Wuhan 4.0071, china 3 Earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi 830011, china 1. Research Center of Space Science and Technology China University of Geosciences Wuhan 430074 China 2. Institute of Seismology China Earthquake Administration Wuhan 430071 China 3. Earthquake Administration of Xinjiang Uygur Autonomous Region Urumqi 830011 China

Based on GPS measurements conducted from 1992.to 2.06, we present the current crustal movement velocity field for approximately 4.0 sites in the Tianshan Mountains and their adjacent areas, and estimate slip rates on the major faults using a 2.D elastic dislocation model. Our studies show slip rates within the range of 1―4.mm/a on the NW-SE trending strike-slip faults (such as Talas-Fergana fault) in the Tianshan Mountains. We also found the slip rates on the approximately WE-SN trending gently-dipping detachment fault vary from 10―13 mm/a for the southwest Tianshan Mountains to 2.5 mm/a for the eastern Tianshan Mountains, and to 6―12.mm/a for the Kyrgrz Tianshan. The GPS velocity field reveals that the total convergence is not uniformly distributed across the Tianshan Mountains, with 80%―90% of the N-S shortening absorbed along the southern and northern edges, and relatively little deformation accommodated within the interior. This first-order feature of strain pattern is explained best by underthrusting of adjacent blocks beneath the Tianshan Mountains along a basal detachment fault. We found the occurrence of historical M7―8 earthquakes somewhere in the locked ramp that connects the creeping and locking segments of the detachment, thereby resulting in elastic strain concentration and accumulation around it. The elastic strain confined in the upper crustal layer above the detachment ultimately releases through infrequent great earthquakes in the Tianshan Mountains, resulting in considerable folding and faulting at their margins. The Tianshan Mountains propagated outward and rose progressively as a wedge-shaped block.

关键词： Tianshan Mountains GPS slip rates tectonic deformation