Petrographic characteristics, LA-ICP-MS zircon U-Pb dating and affinity of Jiehekou Rock Group in Yunzhong Mountain-Guandi Mountain area, Shanxi Province

Lying in Lüliang Mountains area of Shanxi Province, the Jiehekou Rock Group is mainly composed of a suite of meta-argillaceous-arenaceous rocks, with certain amounts of banded marbles and amphibolites. The zircons from garnet-bearing biotite adamellitic gneiss (12LL05-1), schistose biotite quartzite (12LL09-2) and garnet-bearing feldspar quartzite (12LL15-1) from Xiyupi of Guandi Mountain, Dujiaoqu of Loufan and Sanjiaozhen of Yunzhong Mountain were dated by means of LA-ICP-MS. A magmatic crystalline age of 1941±28Ma was obtained for garnet-bearing biotite adamellitic gneiss (12LL05-1). The youngest peak age of the detrital zircons from schistose biotite quartzite (12LL09-2) is 2519.5±6.7Ma. Two significant peak ages of 2143±15Ma and 2599±11Ma were obtained from garnet-bearing feldspar quartzite (12LL15-1). It is inferred from the rock assemblages and geochronological data that the Jiehekou Group in Xiyupi can be correlated with the Jiehekou Group in Jiehekou-Hangao Mountain area, because both of them were formed before 1.94Ga. The Jiehekou Group in Dujiaoqu (Loufan) area might be the counterpart of the Wutai Group that was formed in late Archean. The Jiehekou Group in Sanjiaozhen (Yunzhong Mountain) can be probably correlated with the Yejishan Group and Lanhe Group. It is suggested that a large NNW-NWW dipping ductile shear zone characterized by dextral shearing kinematics occurred along Lanxian-Fangshan-Lüliang, which turned the EW-trending tectonic belt into NNE-trending one.