LA-ICP-MS zircon U-Pb dating and Hf isotopic compositions of rocks from the Sushui complex in Shanxi-Shaanxi border area and their geological significance

The Sushui complex is one of the main component parts of basement rocks in southern North China Craton (NCC). It is typically exposed in Zhongtiaoshan area and has been studied in detail. The Early Precambrian metamorphic basement complex rocks sporadically exposed in Shanxi-Shaanxi border area are traditionally regarded as the western extension and equivalents of Sushui complex in Zhongtiao region. LA-ICP-MS zircon U-Pb dating reveals that the protolithic ages of amphibolite-plagioclase gneiss, diopside-plagioclase gneiss and two-feldspar granite gneiss are 2260 ± 28Ma, 2053 ± 34Ma and 2098 ± 27Ma, respectively, significantly younger than the ages of rocks in Zhongtiaoshan area, suggesting that the Sushui complex was likely formed in Early Paleoproterozoic rather than in Archean. The majority of zircons of the samples have negative ε_Hf(t) values (the lowerest being-6) with two-stage crustal model ages of 2630~2933Ma, which suggests that these samples were derived from recycled Mesoarchean to Neoarchean crust, and continental crustal materials as old as 2630~2933Ma probably preexisted in the Shanxi-Shaanxi border area. These results provide further evidence for the inference that the southern NCC was likely a coherent ancient terrane at the end of the Neoarchean.