Subdivision and Correlation of the Mesoproterozoic Stratigraphy in the Western and Northern Margins of Yangtze Block
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Institute of Geology, Chinese Academy of Geological Sciences,Institute of Geology, Chinese Academy of Geological Sciences,Institute of Geology, Chinese Academy of Geological Sciences,Institute of Geology, Chinese Academy of Geological Sciences

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    Abstract:

    The Mesoproterozoic strata, distributed in the western and northern margin of Yangtze block, have experienced strong deformation and lower to upper greenschistfacies metamorphism. Based on previous study and formation ages, Mesoproterozoic can be divided into two stages: the Early Mesoproterozoic (1.8~1.4Ga) and Late Mesoproterozoic (1.4~1.0Ga). The Early Mesoproterozoic strata (1.8~1.4Ga) contains Dahongshan Group, Dongchuan Group, Hekou Group and Tong’an Formation (1~4 Member), while the Late Mesoproterozoic (1.4~1.0Ga) is composed mainly of Kunyang Group, Huili Group in the southwestern part of the block, and Shennongjia Group and Dagushi Group in the northern part of the block in the Late Mesoproterozoic. New zircon U-Pb geochorology data indicate that the tuff of the Tong’an Formation and the quartz-keratophyrite of the Hekou Group formed at 1744±14Ma and 1659±23Ma, respectively, and the mafic dyke intruded into the Huili Group at 1026±7Ma. According to the sedimentary succession, formation environment and geochronological data, the Dahongshan Group, Dongchuan Group, Hekou Group and Tong’an Formation formed at almost same time and have similar compositions. They all are related to IOCG (Iron-Oxide-CopperGold) or SSC (Sediment-hosted Stratiform Copper) formed in an extensional environment during 1.75~1.45Ga. The Huodiya Group in the northern margin of the Yangtze Block may belong to the Early Mesoproterozoic. Late Mesoproterozoic strata are also present in the western and northern margin of the Yangtze Block, including Kunyang and Huili groups in the southwestern margin of Yangtze Block were formed in 1.2~1.0 Ga; Shennongjia and Dagushi groups in the northern margin of the block formed during 1.4~1.0Ga, with the top of them probably extending to the Early Neoproterozoic. A large amount of stromatolite was also found to occur in the Mesoproterozoic strata, indicating that they formed in a warm, humid shallow sea environment. Besides the Mesoproterozoic strata mentioned above, the Julin Group in the Yuanmou area of Yunnan province, and the Dengxiangying Group and fifth Member of the Tong’an Formation in western Sichuan province all belong to the Late Mesoproterozoic.

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GENG Yuansheng, KUANG Hongwei, LIU Yongqing, DU Lilin.2017. Subdivision and Correlation of the Mesoproterozoic Stratigraphy in the Western and Northern Margins of Yangtze Block[J]. Acta Geologica Sinica,91(10):2151-2174

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History
  • Received:January 19,2017
  • Revised:May 30,2017
  • Adopted:October 26,2017
  • Online: October 26,2017
  • Published: