Study Of Tectonic Thermal Evolution History And Uplift In Mesozoic-cenozoic In The North Rim Of Sichuan Basin

The study area is located in the north of Yangtze platform and in the south of Qinling orogenic belt, which is one of the most important polymetallic metallogenic belt in China and have found several large-very large metal deposits, be rich in Pb, zinc, Au, Cu, Hg, Ag, Sb, Mn, V, U, As and other metal elements. In addition, this area has excellent source rocks, reservoir, cap rock combination conditions, favorable structural trap and reservoir forming conditions,which has a good hydrocarbon potential attracted by people. Stratigraphic controlled epithermal deposit is represented by Pb, zinc formed within 1500 meters in depth, temperature between 50 to 200 centigrade. The tectonic uplift and denudation after deposit formed is very important to its exploration potential evaluation. Similarly, the later tectonic uplift also has important effects on the formation and preservation conditions of oil and gas reservoirs. At present, it is generally believed that tectonic evolution controlled the accumulation characteristics and accumulation pattern of gas reservoir since Mesozoic.This article uses stratigraphic callback technology to restore depositional history in the study area. Dabashan have three stages of evolution experience: ①Basal formation stage from Archean to Proterozoic, the deposition rate is about 6.11 m/Ma in Sinian system; ②the stage of Carbonate platform sedimentary from Cambrian to Permian; ③the stage of Intracontinental orogenic and foreland basin tectonic evolution from Mesozoic to Cenozoic. Beiba vault have three stages evolution experience: ①the basal form and evolution stage; ②The basin tectonic evolution stage in Paleozoic; ③The Mesozoic orogenic tectonic evolution stage.Using apatite fission track to invert thermal history show that Dabashan and Beiba vault began to uplift was 153 Ma and 135 Ma which all influenced by Yanshan movement.The uplift time of Beiba vault was later than Dabashan because the influence of Yanshan movement to Beiba vault was late due to the block of Hannan old land. Dabashan and Beiba vault had been rapidly uplifting during 153 to 80 Ma and it reflected the regional denudation in Cretaceous in the study area. Dabashan foreland and Beiba vault had been extremely fast uplifting and denudating processes in 5 Ma(or 7 Ma), the east and northeast of Qinghai-tibet plateau intensified uplift at the same time,which activated the Qinling old structure again and leded to the Dabashan significant erosioning.This event also had an influence to HannanMicangshan,which was the southern margin of Qinling.In addition,the change of climate environment also had a great effect on the rapid erosion of the research region since Miocene.