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Neoproterozoic Mafic Dykes and Basalts in the Southern Margin of Tarim, Northwest China: Age, Geochemistry and Geodynamic Implications
作者姓名:ZHANG Chuanlin  YANG Dongsheng  WANG Hongyan  DONG Yongguan and YE Haimin
作者单位:ZHANG Chuanlin,WANG Hongyan,DONG Yongguan,YE Haimin(Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China);YANG Dongsheng(Key Laboratory of Metallogenic Dynamics, Guangzhou Institute of Geochemistry, the Chinese Academy of Sciences, Guangzhou 510640, China) 
摘    要:<正>Neoproterozoic rifting-related mafic igneous rocks are widely distributed both in the northern and southern margins of the Tarim Block,NW China.Here we report the geochronology and systematic whole-rock geochemistry of the Neoproterozoic mafic dykes and basalts along the southern margin of Tarim.Our zircon U-Pb age,in combination with stratigraphic constraint on their emplacement ages,indicates that the mafic dykes were crystallized at ca.802 Ma,and the basalt, possibly coeval with the ca.740 Ma volcanic rocks in Quruqtagh in the northern margin of Tarim. Elemental and Nd isotope geochemistry of the mafic dykes and basalts suggest that their primitive magma was derived from asthenospheric mantle(OIB-like) and lithospheric mantle respectively,with variable assimilation of crustal materials.Integrating the data supplied in the present study and that reported previously in the northern margin of Tarim,we recognize two types of mantle sources of the Neoproterozoic mafic igneous rocks in Tarim,namely the matasomatized subcontinental lithospheric mantle(SCLM) in the northern margin and the long-term enriched lithospheric mantle and asthenospheric mantle in the southern margin.A comprehensive synthesis of the Neoproterozoic igneous rocks throughout the Tarim Block led to the recognition of two major episodes of Neoproterozoic igneous activities at ca.820-800 Ma and ca.780-740 Ma,respectively.These two episodes of igneous activities were concurrent with those in many other Rodinian continents and were most likely related to mantle plume activities during the break-up of the Rodinia.

关 键 词:Neoproterozoic  mafic  dyke  swarm  and  basalts    Tarim    breakup  of  the  Rodinia
收稿时间:2009/6/15 0:00:00
修稿时间:2009/12/23 0:00:00

Neoproterozoic Mafic Dykes and Basalts in the Southern Margin of Tarim, Northwest China: Age, Geochemistry and Geodynamic Implications
Authors:ZHANG Chuanlin  YANG Dongsheng  WANG Hongyan  DONG Yongguan  YE Haimin
Institution:1. Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China;2. Key Laboratory of Metallogenic Dynamics, Guangzhou Institute of Geochemistry, the Chinese Academy of Sciences, Guangzhou 510640, China
Abstract:Neoproterozoic rifting-related mafic igneous rocks are widely distributed both in the northern and southern margins of the Tarim Block, NW China. Here we report the geochronology and systematic whole-rock geochemistry of the Neoproterozoic mafic dykes and basalts along the southern margin of Tarim. Our zircon U-Pb age, in combination with stratigraphic constraint on their emplacement ages, indicates that the mafic dykes were crystallized at ca. 802 Ma, and the basalt, possibly coeval with the ca.740 Ma volcanic rocks in Quruqtagh in the northern margin of Tarim. Elemental and Nd isotope geochemistry of the mafic dykes and basalts suggest that their primitive magma was derived from asthenospheric mantle (OIB-like) and lithospheric mantle respectively, with variable assimilation of crustal materials. Integrating the data supplied in the present study and that reported previously in the northern margin of Tarim, we recognize two types of mantle sources of the Neoproterozoic mafic igneous rocks in Tarim, namely the matasomatized subcontinental lithospheric mantle (SCLM) in the northern margin and the long-term enriched lithospheric mantle and asthenospheric mantle in the southern margin. A comprehensive synthesis of the Neoproterozoic igneous rocks throughout the Tarim Block led to the recognition of two major episodes of Neoproterozoic igneous activities at ca. 820-800 Ma and ca. 780-740 Ma, respectively. These two episodes of igneous activities were concurrent with those in many other Rodinian continents and were most likely related to mantle plume activities during the break-up of the Rodinia.
Keywords:Neoproterozoic mafic dyke swarm and basalts  Tarim  breakup of the Rodinia
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