Analysis of proto-type Tarim Basin in the late Precambrian and the dynamic mechanism of its evolution.

Tarim Basin has undergone an intricate tectonic evolution history ever since its formation from two discrete terranes in Neoproterozoic rather than in the Paleoproterozoic. More precisely, the amalgamation is assumed to happen during 1.0-0.8 Ga based on plate affinity. As the beginning of a unified Tarim block, studies of Tarim Basin in the Precambrian are basic and important. After the amalgamation of south and north paleo-Tarim terranes, Tarim block was experiencing a complicated tectonic process of being affected by mantle plume related to the breakup of Rodinia supercontinent in the south, and compressed by the Circum-Rodinia Subduction System in the north. The breakup of Rodinia supercontinent finished in the late Sinian Period, leading Kudi Ocean and Altyn Ocean to open and separating Tarim block from itself. According to the residual strata thickness, drilling data, and lithofacies distribution, the proto-type basin and tectono-paleogeographic maps of Tarim Basin in the late Nanhua Period and Sinian Period are reconstructed. With these maps, the characteristics of the rifts are revealed. Two rift systems were developed inside the unified Tarim Basin in the Nanhua Period and Sinian Period, one back-arc rift system in the northern margin and the other aulacogen system in the southern margin. The azimuth distribution of the rifts in Quruqtagh showed a predominant NE-SW trend, and the rifts in Aksu trended mainly NW-SE, while the rifts in Tiekelike trended SW-NE. With a three-dimensional elastic FEM (Finite Element Method) model that includes all rifts and deposited areas in Tarim Basin, applying the southern subduction and northern mantle upwelling properly to get the paleotectonic mian stress axes and the differential stress field, the dynamic mechanisms of rifts evolution are proved to be related to the peripheral tectonic environment mentioned above.