Characteristics of Magnetic Basement Depth Beneath China Mainland

The relief of the metamorphosed basement of the Precambrian and the thickness variation of the overlying sedimentary cover are very important for geology and exploration of energy and resources. The magnetic difference between these two layers permits geophysicists to estimate the magnetic basement depth using aeromagnetic data. The work is based on such data acquired by AGRS's aero geophysical surveys for more than 30 years over China mainland, covering more than 30 basins and areas. Our purpose is to compile the magnetic basement depth map for China mainland on a scale 1:1000000 with the data converted into the same coordinate system and scale. The resultant map shows that using E105° line as a boundary, the covers are thick in sedimentary depression areas of western China, mainly distributed in the Tarim basin, Junggar basin, Qaidam basin and Tibet area. While, in east China, mainly distributed in the Songliao basin, Erlian basin, Ordos, southern North China, Sichuan basin, and South Yellow Sea-Subei basin, such covers are relatively thin in sedimentary depression areas, of which the largest thickness is located in the southwest of the Sichuan basin and the western edge of the Ordos basin. These characteristics are associated with the metamorphosed basement of Precambrian and depth changes of irruptive rocks body with certain scales, and reflect sedimentary covers' thickness and status. They allow us to intuitively observe depths and sizes of various types of sedimentary basins and sedimentary depression areas, and provide direct evidence for exploration of oil and gas reservoirs on the basements.