A Post-collision Tectonic Activity Model Dominated by Extension:Taking the Dabie Mountain Area as an Example

Understanding process of continent-continent collision is a key to develop the Plate Tectonics. At present, understanding on deep processes of pre-collision is clearer than that of post-collision. The Dabie Mountains are regarded as the Mesozoic orogenic belts that have undergone a complete continent-continent collision and are natural laboratories for understanding tectonic activities in the post-collision. In order to provide a better explanation for tectonic activities in the post-collision, we take Dabie Mountains as research region and comprehensively utilize two deep seismic reflection profiles which across the whole DabieShan orogen，combined with previous studies on ultra-high pressure (UHP) rocks rocks and surface geology, to analyze the crustal geometry of the Dabie orogenic belts. Finally, we have made a series of discoveries as follows: (1) Discoverey of unique discontinuous structure of the Moho;(2) Diapired magmatic domes were found in the mid-crust beneath almost the whole Dabie Mountains;(3) A series of faults formed by the extension of the post-collision;(4) Revealed the exhumation channel through which the ultra-high pressure (UHP) rocks returned to lower-crustal.Through comprehensive research, this paper proposes a post-collision tectonic activity model dominated by extension and summarizes its typical tectonic style.

Key words:post-collision, DabieShan orogen,seismic reflection profiles,ultra-high pressure (UHP) rocks,Diapired magmatic domes,Moho