Paleoproterozoic volcanic rocks in the southern margin of the North China Craton, central China:Implications for the Columbia supercontinent  

作　　者：Changming Wang Xinyu He Emmanuel John M. Carranza Chengmin Cui 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China [2]Centre for Exploration Targeting,University of Western Australia,Perth,Western Australia 6009,Australia [3]China Non-ferrous Metals Resource Geological Survey,Beijing 100012,China [4]Discipline of Geological Sciences,University of KwaZulu-Natal,Westville Campus,Durban 3629,South Africa

出　　处：《Geoscience Frontiers》2019年第4期1543-1560,共18页地学前缘（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41872080);the National Basic Research Program of China(Grant No.2015CB452603);the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Beijing)(Grant No.MSFGPMR201804);and the Fundamental Research Funds for the Central Universities of China(Grant Nos.2652016077,2652017223)

摘　　要：The volcanic rocks of the Xiong’er Group are situated in the southern margin of the North China Craton(NCC).Research on the Xiong er Group is important to understand the tectonic evolution of the NCC and the Columbia supercontinent during the Paleoproterozoic.In this study,to constrain the age of the Xiong’er volcanic rocks and identify its tectonic environment,we report zircon LA-ICP-MS data with Hf isotope,whole-rock major and trace element compositions and Sr-Nd-Pb-Hf isotopes of the volcanic rocks of the Xiong’er Group.The Xiong’er volcanic rocks mainly consist of basaltic andesite,andesite.dacite and rhyolite,with minor basalt.Our new sets of data combined with those from previous studies indicate that Xiong’er volcanism should have lasted from 1827 Ma to 1746 Ma as the major phase of the volcanism.These volcanics have extremely low MgO.Cr and Ni contents,are enriched in LREEs and LILEs but depleted in HFSEs(Nb,Ta,and Ti),similar to arc-related volcanic rocks.They are characterized by negative zirconεHft values of-17.4 to 8.8,whole-rock initial 87Sr/86Sr values of 0.7023 to 0.7177 andεNd(t)values of-10.9 to 6.4.and Pb isotopes(206Pb/204Pb=14.366-16.431,207Pb/204Pb=15.106-15.371,208Pb/204Pb=32.455-37.422).The available elemental and Sr-Nd-Pb-Hf isotope data suggest that the Xiong’er volcanic rocks were sourced from a mantle contaminated by continental crust.The volcanic rocks of the Xiong’er Group might have been generated by high-degree partial melting of a lithospheric mantle that was originally modified by oceanic subduction in the Archean.Thus,we suggest that the subduction-modified lithospheric mantle occurred in an extensional setting during the breakup of the Columbia supercontinent in the Late Paleoproterozoic,rather than in an arc setting.The volcanic rocks of the Xiong’er Group are situated in the southern margin of the North China Craton（NCC）.Research on the Xiong er Group is important to understand the tectonic evolution of the NCC and the Columbia supercontinent during the Paleoproterozoic.In this study,to constrain the age of the Xiong’er volcanic rocks and identify its tectonic environment,we report zircon LA-ICP-MS data with Hf isotope,whole-rock major and trace element compositions and Sr-Nd-Pb-Hf isotopes of the volcanic rocks of the Xiong’er Group.The Xiong’er volcanic rocks mainly consist of basaltic andesite,andesite.dacite and rhyolite,with minor basalt.Our new sets of data combined with those from previous studies indicate that Xiong’er volcanism should have lasted from 1827 Ma to 1746 Ma as the major phase of the volcanism.These volcanics have extremely low MgO.Cr and Ni contents,are enriched in LREEs and LILEs but depleted in HFSEs（Nb,Ta,and Ti）,similar to arc-related volcanic rocks.They are characterized by negative zircon εHft values of-17.4 to 8.8,whole-rock initial 87Sr/86Sr values of 0.7023 to 0.7177 andεNd（t） values of-10.9 to 6.4.and Pb isotopes(206Pb/204Pb =14.366-16.431,207Pb/204Pb =15.106-15.371,208Pb/204Pb= 32.455-37.422).The available elemental and Sr-Nd-Pb-Hf isotope data suggest that the Xiong’er volcanic rocks were sourced from a mantle contaminated by continental crust.The volcanic rocks of the Xiong’er Group might have been generated by high-degree partial melting of a lithospheric mantle that was originally modified by oceanic subduction in the Archean.Thus,we suggest that the subduction-modified lithospheric mantle occurred in an extensional setting during the breakup of the Columbia supercontinent in the Late Paleoproterozoic,rather than in an arc setting.

关 键 词：Volcanic rocks Geochronology Sr-Nd-Pb-Hf isotopes PALEOPROTEROZOIC North China CRATON SUPERCONTINENT COLUMBIA 

分 类 号：P[天文地球]