THE DISTRIBUTION AND DYNAMIC MECHANISM OF NEOPROTEROZOIC BASINS IN NORTH TARIM, WESTERN CHINA

More and more attention has been paid to the Precambrian research on Tarim basin because of the affinity between the Tarim craton and the Australian craton in the Neoproterozoic, two important cratons in Rodinia supercontinent, but the distribution of the north Neoproterozoic basins is still not clear and the dynamic mechanism is controversial.

Based on the outcrops around basin and the latest drilling, seismic and aeromagnetic data, we found the Neoproterozoic wedge-shaped strata, Nanhuan and Sinian, characterized by complete and continuous sedimentary sequences which represent the beginning of deposition and the lowest horizon in the north of Tarim basin. The Neoproterozoic wedge-shaped strata is distributed in EW direction with length of about 600-800km, width of about 200-300km, and its thickness reduced from the middle to the north and south with a maximum thickness of about 3500 to 4000 m in the northeast Manjiaer - Kuruketage area (Manjiaer aulacogen proposed by some scholars) and northwest Awati area (Awati aulacogen proposed by the other scholars).This paper provides the distribution of the north Neoproterozoic basin for the first time.

The distribution of the wedge-shaped strata in basin indicated that the north of Tarim basin has undergone long and narrow rifting in Neoproterozoic, rather than the trigeminal rifting that related to aulacogen, and the basement in the north of the Neoproterozoic basin is composed of I-type granite (ca. 830Ma) in island arc environment according to the data from the deep well XH1. Therefore, the Neoproterozoic basin was formed by back-arc extension in plate subduction that is related to the aggregate event of Rodinia supercontinent. In addition, there is a large number of bimodal volcanic rocks(ca. 740Ma) and great thickness of sedimentary rocks, which indicated a continental rift environment, so the north of Tarim basin is similar to the Australia rifting basin that is formed by the mantle plume in the breakup event of Rodinia supercontinent. In a word, this paper suggests that the plate subduction and mantle plume during the aggregation and breakup of Rodinia supercontinent are the deep dynamic mechanism of the north Tarim basin in Neoproterozoic.