Abstract

Responses to the India-Eurasia plate collision vary significantly in different regions. In Southeastern Tibetan Plateau, the tectonic extrusion of the Sundaland block accommodated the tectonic convergence between the two plates. However, there have been extensive controversies over the mechanism of extrusion of the block. In this study, we focus on macro- and micro-scopic structural analysis, kinematics, timing of shearing and thermal histories of several typical metamorphic complexes in order to understand the tectonic processes driving the deformation of the complexes and extrusion of the block. It is shown that dome structures cored by the metamorphic rocks are widely developed in Southeast Tibetan Plateau. The cores are composed of high-grade metamorphic and high temperature deformed rocks, while the mantle parts are characterized by low-grade metamorphic rocks and low temperature deformation. Thermochronological data reveal that most of the domes began to be exhumed since 30 Ma, while the initiation of doming was diachronous at different places and mostly through two-stage cooling histories. In most of the domes, shear discontinuities exist between the core and mantle parts. We show that the formation and exhumation of the dome structures are related to subhorizontal middle and lower crustal flow, during which shearing, folding and exhumation are simultaneous. The middle and lower crustal flow resulted in lateral crustal flow and vertical exhumation of crustal masses, which absorbed a large amount of deformation of the lateral escape of Sundaland block during India-Eurasia collision.