The Tectonic Characteristics Of Bogeda Mountain And Its Orogeny At Mesozoic-Cenozoic Time

The Cenozoic Bogeda mountain is taken as the representative intracontinental orogen, and the studies on its tectonic evolution and structural deformation are very useful both for petroleum exploration in this area and for understanding of intra-continental deformation mechanism. In this paper, with the application of advanced technicals and methods, i.e. structural-sedimentary recycle analysis, provenance analysis, balanced cross sections, apatite fission-track analysis, et. al., the much systemic researches on the orogeny, evolution of Bogeda mountain have been carried out by means of the structural geology , petrology and chronology. Results obtained in the research include followings:1. There are many disputations about the geological setting in Carboniferous of the Bogeda Mountain, such as small oceanic basin, aulacogen, rift or Island-Arc and so on. Based on the geochemical anylysis combining other data, the author thinks it was aulacogen during Carboniferous period. The pre-Mesozoic evolution in this area have experienced six stages of tectonic evolution.2. Starting with the research on the widely distribution of thrust tectoncs and analysis on the combination of folds with faults, the evolution of thrust sequence, the combination of different structural styles, the Cenozoic re-orogeny of the Bogeda Mountain and its expression are discussed detailedly. Longitudinally, the fold-thrust zone is classified into three belts, i.e. the overthrust belt, the basement-involved belt and the decollement belt; Latitudinally, the basement- involved fold-thrust belt can be divided into two sections; Sectionally, the decollement belt holds double-deck or three-deck structures.3. The regional stress field is mainly marked by compression with N-S direction; The thrusting direction is characterized by the direction from south to north. The propagation sequences of thrusts are characteristics of both the piggyback in the decollement thrust-folds and the overstep in the basement-involved thrust-folds. Thus, the structural deformation occurred at the end of Pliocene to early Pleistocene as well as at the end of Jurassic, and the shortening ratio of crust is 38～41% in the Bogeda area. The ratio in the west part is bigger than that in the east part.4. By the means of uncomformity analysis, heavy mineral analysis, detrital framework analysis, paleocurrent analysis , thermal chronology, et. Al, the Mesozoic-Cenozoic uplift history of Bogeda Mountain is analyzed, there are 3 obvious uplift events from the beginning of Cebozoic period. About the geodynamics in Bogeda Mountain, we think that the strong...