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Underplating in the middle-lower Yangtze Valley and model of geodynamic evolution:Constraints from geophysical data

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Science china Earth Sciences 2005年第7期48卷 985-999页

作者： Lü Qingtian, HOU Zengqian, YANG Zhusen & SHI Danian institute of mineral resources,Chinese Academy of Geological Sciences,beijing 100037,china institute of mineral resources Chinese Academy of Geoloqical Sciences Beijina 100037 China

The lower crust and Moho are the most active boundary layers in the process of continental evolution, in which marks left by tectonic and magmatic activities during the process are preserved. The evolutionary process of the continental lithosphere may be reconstructed by exploring the structures of the lower crust and Moho. According to a study of the deep seismic reflection data obtained from the middle-lower Yangtze Valley, the authors find bright layered reflections ubiquitous in the lower crust and think that the bright reflections are caused by un-derplating of basic or ultrabasic magmas, which might be related to delamination of the lithosphere. On the basis of an integrated analysis of the geophysical and geological data of the region, the authors propose a model for geodynamic evolution of the middle-lower Yangtze Valley. This model suggests that the middle-lower Yangtze Valley had undergone such geodynamic processes as collision-compression, delamination-extension and underplating-melting since the end of the Permian, finally forming the gigantic middle-lower Yangtze Valley metallogenic belt.

关键词： lower crust deep seismic reflection underplating tectonic evolution.

REE Geochemistry in the Weathered Crust of Granites, Longnan Area,Jiangxi Province

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Acta Geologica Sinica(English Edition) 1990年第2期64卷 193-209,237页

作者： Wu Chengyu Huang Dianhao Guo Zhongxun institute of mineral Deposits, Chinese Academy of Geological Sciences, beijing Geological Survey Party of South Jiangxi, Jiangxi Bureau of geology and mineral resources, Ganzhou, Jiangxi Chinese Academy of Geological Sciences Beijing China

Warm and humid climate and gentle hilly topography have provided favourable conditions for the devel-opment of the weathering crust of the granite intrusions in the Longnan area, Jiangxi Province. REE is mostlyconcentrated in an adsorption state in clay in the wholly weathered zone. The rare-earth minerals enriched inthe parent rocks provided the source material for the REE enrichment. Exchangeable REE accounts for48-86%. Extraction experiments and stable isotopic study of clay minerals suggest that the downward infiltra-tion of meteoric water and increasing gradient of pH values have played an important role in the enrichment ofREE during the progressive weathering. Slight fractionation of individual REE can not change their distribu-tion patterns in the profiles. which are inherited from the parent rocks.

关键词： REE Geochemistry in the Weathered Crust of Granites Longnan Area,Jiangxi Province

Carbon isotopic variations of Proterozoic carbonates in Jixian, Tianjin, china

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Science china Earth Sciences 2004年第2期47卷 160-170页

作者： CHU Xuelei, ZHANG Tonggang, ZHANG Qirui, FENG Lianjun & ZHANG Fusong1. institute of geology and Geophysics, Chinese Academy of Sciences, beijing 100029, china 2. Key Laboratory for mineral resources Research, Chinese Academy of Sciences, beijing 100029, china Correspondence should be addressed to Chu Xuelei (email: xlchu@***) institute of geology and Geophysics Chinese Academy of Sciences Beijing China Key Laboratory for mineral resources Research Chinese Academy of Sciences Beijing China

Along the Proterozoic stratigraphic sections of Jixian, Tianjin, the ??13C values of carbonates are mostly negative in the Changchengian (Changcheng System), varying approximately within a range of (0±1)‰ in the Jixianian (Jixian System), and have commonly positive values of (2±2)‰ in the Qingbaikouan (Qingbaikou System). From Chuanlinggou Formation to Dahongyu Formation, i.e. from ca. 1700 Ma to 1600 Ma, the δ13C values of carbonates increase from about -3‰ to 0‰, but oscillate with large excursion in Dahongyu Formation. Two large excursions occur in the Jixianian, one in Yangzhuang Formation and the other in the third submember of Wumishan Formation overlaying. These integrated and continuous records of carbon isotope reflect secular variations of δ13C value in ancient seawater from ca. 1700 Ma to ca. 800 Ma. The increase and subsequent oscillation of seawater δ13C value occurring from the ages of ca. 1700 to ca. 1600 Ma and ＜1300 Ma may signify two correlative global tectonic events.

关键词： Proterozoic, Jixian, carbon isotope, chemostratigraphy, secular variation, global tectonic event.

SHRIMP U-Pb dating and Hf isotopic analyses of Middle Ordovician meta-cumulate gabbro in central Qiangtang, northern Tibetan Plateau

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Science china Earth Sciences 2010年第5期53卷 657-664页

作者： ZHAI QingGuo1 WANG Jun1, LI Cai2 & SU Li3 1 institute of geology, Chinese Academy of Geological Sciences, beijing 100037, china 2 College of Earth Sciences, Jilin University, Changchun 130061, china 3 The Geological Laboratory Center and State Key Laboratory of Geological Processes and mineral resources, china University of Geo- sciences, beijing 100083, china institute of geology Chinese Academy of Geological Sciences Beijing China College of Earth Sciences Jilin University Changchun China The Geological Laboratory Center and State Key Laboratory of Geological Processes and mineral resources China University of Geosciences Beijing China

Metabasites consisting of metamorphic ultra-mafic rocks, cumulate gabbro, gabbro (diabase), basalt, and plagiogranite are exposed at the Taoxinghu area in central Qiangtang, northern Tibetan Plateau. Zircon SHRIMP U-Pb dating for the cumulate gabbro yields a weighted mean age of 467±4 Ma, which is the oldest and most reliable magmatic age in this area. Zircon 176Hf/177Hf ratios range from 0.282615 to 0.282657, with εHf(t) values of 5.02±0.28, indicating that the cumulate gabbro was mainly derived from the depleted mantle. In addition, geochemical data of metabasites suggest that they have similar characteristics to those in the mid-ocean ridge basalts (MORB). The Taoxinghu metabasites may represent the fragment of Early Paleozoic ophiolite in the "Central Uplift" of the Qiangtang, northern Tibetan Plateau.

关键词： Qiangtang cumulate gabbro SHRIMP dating Hf isotope

Discovery of seismites in Upper Sinian stratiform lead-zinc deposits in Dadu River valley, Sichuan, china: Implication for ore genesis

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Science china Earth Sciences 2006年第11期49卷 1135-1146页

作者： LIN Fangcheng1,2 & PAN Guitang2 1. Geoscience College, Chengdu University of Technology, Chengdu 610059, china 2. Chengdu institute of geology and mineral resources, Chengdu 610082, china Geoscience College Chengdu University of Technology Chengdu China Chengdu institute of geology and mineral resources Chengdu China

A number of lead-zinc sulphide deposits have been discovered in recent years in dolo- mitic rocks of the Upper Sinian Dengying Formation in the Dadu River valley region, Sichuan Province, china. The lead-zinc mineralization is closely associated with a black siliceous exhalite that has been traced over 50 km of strike. This makes Dadu River valley the most extensive stratiform non-ferrous sulphide horizon having been discovered to date in china. In a previous study by the first author (LIN), these deposits were recognised as belonging to the broad spectrum of lead-zinc sedimentary exhala- tive (SEDEX) deposits. In this paper, seismites and seismogenetic structures occurring in close association with the Dadu River valley mineralized zone are described. The close spatial and temporal relationship between the seismites and mineralization provides strong evidence for the hypothesis that the lead-zinc SEDEX deposits formed in direct response to earthquake activities around the Sinian-Cambrian boundary. The earthquakes are postulated to be an effective dynamic mechanism for triggering the upward migration of deep circulating ore fluids along synsedimentary growth faults and their exhalation onto the sea-floor to form the extensive deposits of stratiform lead-zinc sulphide ore.

关键词： seismites, earthquake, lead-zinc deposit, hydrothermal exhalation, Upper Sinian Dengying Age.

ESR and U-series ages of coral reef samples from shallow drill holes in the South china Sea

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Acta Oceanologica Sinica 1991年第3期10卷 423-431页

作者： Ye Yuguang, Gao Juncheng, He jie, Diao Shaobo, Liu Xinbo and Du Yajing institute of Marine geology, Ministry of geology and mineral resources, Qingdao, 266071, chinaNational institute of Metrology, beijing, 100013, china institute of Marine geology Ministry of Geology & Mineral Resources Qingdao 266071 China.

The ages of coral reef samples from several shallow drill holes in the South china Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ages and that the coral reefs were formed in the early Holocene. In the determination of natural total dose of coral reef by use of the additive dose method good results can be obtained by exponential fitting, no matter how the effect of dose saturation is. It was found that the ratio of the natural ESR signal intensity ( I0) to the ESR signal intensity at dose saturation ( Imax) of sample can reflect the significance of a irradiation efficiency-k value. Using the k value of sample determined by the formula given in this paper, the precision of ESR dating of marine carbonates can be improved.

关键词： Th ESR and U-series ages of coral reef samples from shallow drill holes in the South china Sea

A Scheme of the Hierarchy for Sequence Stratigraphy

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Journal of Earth Science 1996年第1期15卷 1-12页

作者： Wang Hongzhen Shi Xiaoying (Department of geology and mineral resources, china University of Geosciences, beijing 100083)

Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.

关键词： hierarchy sequence stratigraphy,eustatic cycle cosmological cycle.

Mantle-derived rare-gas releasing features at the Tianchi volcanic area, Changbaishan Mountains

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Chinese Science Bulletin 1997年第9期42卷 768-771页

作者： SHANGGUAN Zhiguan and SUN Mingliang1. institute of geology, State Seismological Bureau, beijing 100029, china 2. Lanzhou institute of geology, Chinese Academy of Sciences, Lanzhou 730000, china institute of geology State Seismological Bureau Beijing China Lanzhou institute of geology Chinese Academy of Sciences Lanzhou China

TIANCHI volcano,Changbaishan Mountains isthe largest modern active volcano in East *** times strong volcanic erupting activ-ities occurred in the Cenozoic *** vol-canic activities have revived again in the *** investi... 详细信息

关键词： Tianchi volcanic area Changbaishan Mountains mantle-derived rare gas 3He/ 4He 40 Ar/36 Ar 4He/20 Ne 4He/40Ar isotope ratios.

Implications of micro-compositions of garnet and biotite from high-grade meta-pelites

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Progress in Natural Science:Materials International 2006年第2期16卷 209-214页

作者： ZHOU Xiwen, WEI Chunjing, and ZHANG Shangkun ( institute of geology, CAGS, beijing 100037, china School of Earth and Space Sciences, Peking University, beijing 100871, china china University of Geo-Sciences, beijing 100083, china) institute of geology CAGS Beijing 100037 China School of Earth and Space Sciences Peking University Beijing 100871 China china University of Geo-Sciences Beijing 100083 China

Based on detailed studies on the compositional zoning of garnet and biotite in pelitic rocks from the Jingshan group of granulite facies in north Jiaodong, P-T pseudosections with isopleths of Fe/(Fe + Mg) in garnet and biotite were calculated in the KF-MASH system for two representative rocks of sillimanite-garnet-cordierite-biotite gneiss ( Vbi/ Vg>1 ) and sillimanite-garnet gneiss (Vbi/ Vg2) using the software THERMOCALC and the internally consistent thermodynamic dataset. With a comparison of the calculated Fe/(Fe+ Mg) values in garnet and biotite in the peak P-T fields constrained by peak mineral assemblages with the measured ones, it is concluded that the coarse garnet crystals with diffusion zoning from high grade meta-pelites can preserve their peak compositions even when they have experienced a cooling event, and that biotite crystals surrounded by fetsic minerals in biotite-rich rocks with Vbi/Vg> 1 can nearly preserve their peak compositions, and biotites in garnet-rich rocks with Vbi/Vg2 cannot preserve their peak compositions due to the influence of grain-boundary fluid.

关键词： high-grade meta-pelites THERMOCALC P-T pseudosection peak compositions of garnet and biotite.