Abstract:

Orogenic extrusion tectonics is referred to a process that faultbounded deepseated metamorphic complexes returned and deformed under orogenic vertical and/or lateral stress. The previous researches generally focused on geometry and deformation style of extrusion blocks, bounding faults, paths of extrusion and dynamics, the purpose of which was to try to explain the exhumation of deepseated metamorphic complexes in an orogen. Based on the relationship between the movement direction of extrusion block and the strike of orogenic belt, the orogenic extrusion tectonics are divided into seven endmember types (type Ⅰtype Ⅶ) in threedimensional spherical coordinate system, LxLyLz. Lx represents the strike of an orogen or a subduction zone, and Ly is horizontal and perpendicular to Lx, and Lz is perpendicular to a plane composed by Lx and Ly. The combination of these endmembers and transition types can provide a detailed interpretation of extrusion of the Dabie high/ultrahighpressure rocks. Eclogitefacies extrusion ranges from  type  Ⅳ to  type  Ⅶ extrusion, and amphibolitefacies extrusion varies from  type Ⅱ to  type Ⅵ extrusion, which probably indicates that there was possibility of channel flow during this stage. And  type Ⅴ extrusion could be suitable for greenschistfacies extrusion in the Dabie Orogen.

Key words:  extrusion, exhumation, Dabie Shan, high/ultrahighpressure rocks, deformation