SPATIAL AND TEMPORAL DEFORMATION SEQUENCES OF DABA SHAN FTB AND ITS RELATIONSHIPS WITH ADJACENT TECTONIC UNITS, CENTRAL CHINA

Daba Shan is a fold-and-thrust belt (FTB) located on the northeastern margin of the Sichuan Basin, central China. It is the transitional zone between the Sichuan Basin and Qinling orogenic belt, and it is located in the middle part of the Mianlu suture zone which is the boundary between the Qinling orogenic belt and Yangtze block. The Mianlue suture adjoins the exposure of the UHPM rocks in its northeastern end, and was exposed in the middle as the Chengkou Fault which splits Daba Shan FTB into northern and southern units. Discovery of the Mianlue suture zone is of great importance, in that it is significant for the tectonic exploration of the continental amalgamation processes within the Qinling-Dabie orogenic belt during the Mesozoic time. In this talk, I will test the hypothesis with help of three methodologies. First, with the interpretation of four seismic lines (~ 100 km each) which cross the Daba Shan FTB in cooperation of PetroChina, the structural analysis of the Daba Shan FTB is constructed. Second, according to the field mapping carried out in the central and northeastern Daba Shan FTB, the geometric characteristics of geologic structures and distribution of features for the different structural segments have been constrained from surface structural features obtained from field mapping integrated with GIS and satellite image analysis. Balanced cross-sections are built to restore the structural geometry before collision to show the kinematic evolution relationship between the East Qinling orogen and the northeastern Sichuan basin. Based on both the large-scale structural analysis of ASTER remote sensing images and the small-scale field mapping and structural analysis data, structural evolution models are made to reveal the geometric and kinematic relationships of Daba Shan FTB with adjacent areas. Third, the ⁴⁰Ar/³⁹Ar dating of syn-faulting minerals exposed along Major Chengkou Fault will be used to determine the deformation periods. A comprehensive model is made to determine spatial and temporal deformation sequences on Daba Shan FTB to understand the kinematic relationships of the syn- to post-collisional tectonic evolution between the Qinling-Dabie orogenic belt and the Sichuan Basin. The interactive relationships among them will contribute to reveal the exhumation mechanism of the Dabie Shan UHPM rocks.