Dynamic Mechanism Research on the Tectonic Activation of Anninghe Rift

Abstract

Anninghe rift is located on the western edge of Yangtze Block next to Tibetan Plateau, along the axis of a continental paleorift zone, Panxi paleorift. Recent studies have found that an upward mantle convection system existed since the late Pliocene in the deep lithosphere of a long and narrow area controlled by Anninghe fault. Lithospheric temperature distribution in the area has characteristics similar to that in Baikal and other modern rifts. A mantle upwelling area was in a constant state of “pull-subsidence.” Brittle rock mass of the shallow crust cracked into the new secondary subsidence blocks. A thick lacustrine sedimentary sequence of continental subsidence type developed. These all indicate that Anninghe rift is in an obvious tectonic activation state. It is believed that the tectonic activation of Anninghe rift has been produced by both horizontal squeeze from a plastic flow of the upper crust and expansion from mantle uplift. The pressure from the plastic flow of the upper crust is slightly greater than the expansion stress from the uplifting of lithosphere. Under this specific geodynamic environment, whether the tectonic activation of Anninghe rift can continue depends on the thermal motion rate of deep mantle materials and the eastward migration of the crustal materials of Tibetan Plateau.