Constraints on the craton-orogen boundary in the northern Liaoning Province:Evidence from zircon Hf isotopes of the late Paleozoic-early Mesozoic granitoids
The northern margin of the North China Block consists of the Bainaimiao arc belt in the north,and the North China Craton in the south with the Bayan Obo-Duolun-Chifeng-Kaiyuan fault as the craton-orogen boundary.However,the location of this boundary in the northern Liaoning Province has not been well constrained.The Bainaimiao arc is an island arc with different basement compositions and evolution history from the North China Craton,and the magmatic rocks(mainly intermediate-acid magmatic rocks)have different Nd-Hf isotopic compositions in these two tectonic units.This paper presents new LA-ICP-MS zircon U-Pb geochronological and Hf isotopic data of late Paleozoic-early Mesozoic granitoids widely exposed in the northern Liaoning Province.The Hf isotopic composition of zircons from Carboniferous and Permian-Early Triassic granitoid rocks located on the Bainaimiao arc and the northern North China Craton is significantly different.The εHf(t)values of the former are positive and the mean crustal model ages TDM are generally less than 1.0 Ga.The εHf(t)values of the latter are negative and the mean crustal model ages TDM are generally greater than 2.2 Ga.Although the Hf isotopic composition of zircons from the middle Triassic granitic rocks varies widely,and there are a few overlapping regions,they still show different characteristics in general.The zircon Hf isotopic compositions of Carboniferous-middle Triassic granitoids from the northern Liaoning Province,combined with the distribution range of Archean-Paleoproterozoic metamorphic crystalline basement rocks,showing that the craton-orogen boundary in the northern Liaoning Province is located 60 km to the north of Fuxin-southwest Zhangwu-northern Xinmin-southern Faku-western Tieling-eastern Kaiyuan-Qinghe fault.
North China CratonBainaimiao arccraton-orogen boundarygranitoidzircon Hf isotope
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