Research On The Tectonic Event And Thermal Evolution History Of Piedmont Zone In Northen Margin Of Junggar Basin

The tectonic evolution and the tectonic thermal evolution history of northen margin of Junggar Basin not only was a hot field in the research on the evolution history of ancient Asian ocean and intra continental deformation in meso-cenozoic, but also was the important question of piedmont zone petroleum exploration. By the integrated study of unconformity event, tectonic thermal chronology and tectonic thermal evolution history, The characteristics of fracture structure, tectonic sequence framework, the pack-age of tectonic event and tectonic thermal evolution history are analysised, and the model of tectonic thermal evolution history of study area is built.(1) Based on the geological field investigation and zircon U-Pb dating, as well as the regional gravity-magnetic date and the tectonic-thermal chronological date of ophiolites and the granites, the characteristics of the faulted structure belt, basement component, tectonic-unit division and rock-stratigraphic units in Northen Junggar Basin were revealed. Also, some new evidences of existing Precambrian Crystalline Basement in Junggar basin were presented.(2) By the distribution characteristic of unconformity event on the northen Junggar Basin, tectonic sequence framework is built. Furthermore, the rock-stratigraphic unit since late paleozic is divided into two tectonic layer series, "basin low metamorphic basement and basin sedimentary cover", and basin sedimentary cover is divided into hercynian, indo-chinese epoch, Yanshan geological period and himalayan period stratigraphic formation and its corresponding nine tectonic layer.(3) Through the analysis of the single grain zircon u-pb ages dating and the fission track dating, combining the dating of tectonic thermal chronology of paleozoic ophiolite and diffrernt type of granites in the northen basin. The relationship of the peak-age coordinate and the unconformity tectonic event is revealed. The result indicate that the subduction and collision of ancient ocean basin closure event happened in 315Ma±, the peak-age of the extension event of continental rift vally after collision is 290±, the peak-ages of deformational event of polycyclic continental rift is 210Ma±in the late indo-chinese epoch, 170 Ma±and 145Ma±in the medium-term of Yanshan geological period, 100Ma±in the late of Yanshan geological period.(4) The model of the tectonic thermal evolution history on northen margin of Junggar Basin is established by the AFT simulation of thermal evolution history and the recovery of the paleo temperature gradient. The result revealed that the thermal evolution history in the study area include five stages: high abnormal type of paleo-geothermal field stage in late carboniferous to early permian, mid-high stable type paleo-geothermal field stage in mid-late permian to triassic, low concave type paleo-geothermal field stage in early-middle jurassic, high convex type of paleo-geothermal field stage in late jurassic to early cretaceous and slowly type of paleo-geothermal field stage after late cretaceous.