The Provenance characteristics of Tongshan Formation in north Zalantun area of the Da Hinggan Mountains：The constraint of geochemistry and LA-MC-ICPMS U-Pb dating of detrital zircons

Abstract：The Tongshan Formation is a very important part of Zalantun-Duobaoshan island arc tectonic belt in northern Zalantun area of the Da Hinggan Mountains. The properties, deposition epoch and tectonic environment type of the source area of Tongshan Formation are important links in the study of the island arc tectonic belt, and also constitute an important window in the study of early tectonic evolution of the old Asian Ocean tectonic domain. Studies of fine elastic rocks and petrography of the Tongshan Formation in combination with geochemistry of the main elements and trace elements in fine elastic rocks show that Tongshan Formation was formed in the continental island arc area or active continental margin as well as the nearby places, and the source materials of Tongshan Formation were mainly felsic rocks and migmatitic felsic rocks formed by the transition from the upper crust to the edge of the andesite island arc, with part of the source material probably derived from the mixture of a small amount of passive continental margin material. The LA-MC-ICPMS zircon U-Pb age spectrum characteristics of fine elastic rocks in Tongshan Formation were determined for the first time, and the results show the diversity of the source area of Tongshan Formation. The U-Pb age spectrum contains 566~632Ma and 789~889Ma detrital zircons and, in combination with regional chronologic information, these data suggest that there must have existed the Neoproterozoic crystalline basement and the Neoproterozoic magmatism and metamorphism in this area, which constituted the main provenances of sedimentary rocks in Tongshan Formation. 2543~2705 Ma and 1773~2120 Ma ancient detrital zircons information revealed in the Xing-Meng orogenic belt suggests the probable existence of Precambrian micro-landmass basement, which became the important provenances of sedimentary rocks in Tongshan Formation. According to 572±5Ma concordant age, in combination with regional contrast, the deposition time of Tongshan Formation was dated at early Ordovician. The research results provide an important basic material for determining the evolution of the early Paleozoic Zalantun-Duobaoshan island arc tectonic belt and also offer a new constraint for the investigation of the continental crustal evolution on the southern margin of the Siberia plate and the researches on tectonodynamics.