Formation and Evolution History on the Great Hingan Mountains:The evidences from Compositions of Rivers’ Overbank Sediments and their Zircon U-Pb Ages, Hf Isotopic Compositions
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    Abstract:

    Through systematic study of geochemistry, zircon U-Pb dating and Hf isotopic compositions on rivers’ overbank sediments in the Great Hingan Mountains, southeast segment of Palaeozoic Central Asian Orogen, it shows that REE and other trace elemental characteristics of the sediments are consistent with those of upper crust. There exist significant differences in contents of mineralized elements between northern and southern segments, which may indicate different mineralization for corresponding elements in different segments. The overbank sediment in the Xar Moron River indicates significant contribution of material from the northern margin of the North China Plate whatever is based on its content of SiO2 or Nd isotopic composition. The most northerly sediment of the Nanweng river also shows the contribution of material from the Precambrian micro-continental block attached to the Siberian Plate on the basis of Nd isotopic composition. Average Nd depleted mantle model age of bulk sediments is almost consistent with that of Hf depleted model ages of zircons, which are 1.03Ga, 1.01Ga,respectively. The oldest zircon U-Pb age is 2473Ma, corresponding Hf depleted model age of which is 3.75Ga. Therefore, the basements of micro-continental blocks of the Great Hingan Mountains were formed during Paleo-proterozoic by intra-continental magmatism of precursor block (3.75Ga). The micro-continental blocks began to separate from the parent block during Mid-proterozoic, which may be a prelude of the Paleo-Asian ocean’s opening. The most intensive crustal accretion from the depleted mantle to the regional crust took place during the period of Neo-proterozoic-Mid-proterozoic to Late Early Paleozoic, which consists of oceanic crusts of Paleo-Asian Ocean and underplating mafic-ultramafic rocks beneath the micro-continental blocks. The Paleo-Asian Oceanic crusts subducted to the Siberian Plate in north and to the North China Plate in south primarily during Late Paleozoic. The ocean disappeared during Late Permian, when intra-continental mountain-building started. The underplating mafic-ultramafic rocks beneath the micro-blocks were partially molten affected by Paleo-Pacific tectonic regime during Mesozoic. Simultaneously,part of basements involved in the magmatism. Mesozoic volcanic and intrusive rocks consist of 80% present occurring crust. But there is no direct contribution of material from depleted mantle during the magmatism.

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Chen Yuelong.2014. Formation and Evolution History on the Great Hingan Mountains:The evidences from Compositions of Rivers’ Overbank Sediments and their Zircon U-Pb Ages, Hf Isotopic Compositions[J]. Acta Geologica Sinica,88(1):1-14

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History
  • Received:April 26,2013
  • Revised:August 29,2013
  • Adopted:September 09,2013
  • Online: January 24,2014
  • Published: