Changes of Jurassic provenance system in Turpan depression and its oil and gas exploration significance

In order to clarify the characteristics of Jurassic provenance system in Turpan depression, based on the evidences of heavy mineral characteristics, sand detrital components, element geochemistry, U-Pb dating of detrital zircon, the provenance direction and depositional system in the Middle East of the depression were studied systematically from different perspectives. It is considered that there are two major provenance areas in the middle and lower Jurassic, and there are obvious differences in the main provenance systems in different parts and periods of the depression. The change of provenance controls the evolution of sedimentary system, and the Northern Piedmont is a new field for oil exploration. The results show that in the early and middle period of Shuixigou group, the source directions of light and heavy minerals and source rock discrimination diagrams(such as La-Th,La/Yb-∑REE ) are consistent. The main peak value of zircon age in the northern part of the depression is (297±2) Ma, and the secondary peak value is (427±4)Ma, corresponding to the 2-stage tectonothermal events. Controlled by the long provenance in the south margin, the depression developed a NW-SE trending far source and long axis delta sedimentary system. The Bogda area in the north is a catchment sedimentary area. The geochemical indexes of mudstone such as V/V+Ni, V/Cr and Ni/Co indicate that the paleo water medium is a reducing environment, which is conducive to the formation of oil and gas. In the late Shuixigou and Sanjianfang sedimentary periods, the heavy mineral and clastic components are obviously zoned, and the provenance and sedimentary environment in the northern part of the depression are characterized by near source sedimentation. The main provenance is from Bogda mountain, indicating that the late Shuixigou is the initial time for Bogda mountain to rise again. © 2020, Editorial Board of Journal of CUMT. All right reserved.