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《Earth Science》 2018-07
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The Discovery and Geological Significance of the Neoproterozoic A_1-Type Granite in the Pailou Area,Wudang Uplift

Zhang Weifeng;Xu Daliang;Peng Lianhong;Deng Xin;Liu Hao;Jin Xinbiao;Tan Jing;Wuhan Center of China Geological Survey;Research Center of Granitic Diagenesis and Mineralization,China Geological Survey;  
As a typical case of the Neoproterozoic magmatism in South Qinling,the Pailou porphyritic monzogranite exposed in the western margin of Wudang uplift.Zircon U-Pb dating on the granite yields an age of 667.2±3.5 Ma.The granite shows subalkaline and metaluminous affinities,with Na_2O+K_2O and A/CNK values ranging 8.31%-8.47% and 0.89-0.94,respectively.The monzogranite enriched in LILEs(i.e.Rb,K,U and Pb)and HFSEs(i.e.Nb and Ti),and depleted in Sr,P,Ti and HREE.Due to the high content of Zr+Nb+Y+Ce and ratios of 10 000 Ga/Al and FeOT/(FeOT+MgO),as well as characteristic minerals of hastingsite and ferropargasite,the Pailou monzogranite displaying A1-type geochemical features.The zirconεHf(t)values of the study rocks mainly vary from -1.8 to +1.5,indicating that the magma likely to have been sourced from mantle metasomatized by asthenosphere,OIB-like melts,with minor crustal assimilation.Based on modal calculations of trace elements,the fractional crystallization of plagioclase and pyroxene has been proposed during magmatic evolution.Integrating the data obtained from studies on geology,geochronology,geochemistry and isotopic compositions,we propose that the Pailou magmatism was the product of norogenic magmatism and formed in tectonic setting of a back-arc rift setting that proba-bly developed in relation to slab tearing during continued slab rollback.
【Fund】: 中国地质调查局项目(No.DD20160030)
【CateGory Index】: P534.3;P588.121
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