Geochemical characteristics of the Middle-Late Permian sedimentary rocks in the southern Great Xing'an Range, NE China, and their constraints on the closure time of the Paleo Asian Ocean (Eastern Segment)

The Late Paleozoic sedimentary environment in the southern Great Xing'an Range in Northeast (NE) China, and the timing of the final closure of the Paleo Asian Ocean between the North China Craton and combined NE China blocks have been controversial for a long time, affecting and restricting the exploration and development of new area and new strata in the North Area in China. In order to reconstruct the structural-sedimentary evolution his-tory of the southern Great Xing'an Range during the Middle to Late Permian, and to explore the closure time of the Paleo Asian Ocean (Eastern Segment), in this paper, the sedimentary characteristics and tectonic background of the Middle-Late Permian sedimentary rocks from well MKD1 are systematically analyzed by using elemental and organic geochemistry methods. The results show that the Middle Permian sedimentary records in well MKD1 show typical marine sediments, while the Late Permian sediments change significantly to clastic rocks de-posited in the marine-continental transitional environment. The provenances of the Middle Permian rocks are mainly intermediate and felsic igneous rocks from continental active margin and oceanic island arc tectonic set-ting, related to the northern accretion complex, and the Songnen Block and partially arc magmatic rock. The source materials of the Late Permian rocks are mainly felsic rocks and some intermediate igneous rocks from the continental arc and active margin, related to the northern accretion complex, the arc magmatic rock and the Songnen Block. Depositional discontinuity after the Late Permian, regional lackness of the Early Triassic strata, sedimentary environment variation, tectonic setting and provenance location discrimination of the Middle-Late Permian rocks comprehensively reveal that the Paleo Asian Ocean (Eastern Segment) possibly closed in the late Late Permian. Finally, we propose a structural-sedimentary evolution pattern of the southern Great Xing'an Range during the Middle to Late Permian.