中国陆域磁性基底深度及其特征

前寒武纪变质基底的起伏变化特征和沉积盖层的厚度变化对研究地质构造、能源和资源勘探具有重要意义.而前寒武纪变质基底与沉积盖层之间通常存在一定的磁性差异,这就为利用航磁资料研究磁性基底深度提供了地球物理条件.本文集合了中国国土资源航空物探遥感中心30多年来编制的中国陆域30多个盆地和地区的磁性基底深度图以及补算的部分地区磁性基底深度,经过统一坐标系、统一比例尺之后编制了1/100万比例尺的中国陆域磁性基底深度图(成图比例尺为1/250万).研究结果表明,以E105°线为界,我国西部地区沉积坳陷区盖层厚度大,集中分布在塔里木盆地、准噶尔盆地、柴达木盆地和西藏地区;东部地区沉积坳陷区盖层厚度整体上相对较薄,主要分布在松辽盆地、二连盆地、鄂尔多斯盆地、华北南部盆地、四川盆地、南黄海—苏北盆地等,但最厚处在四川盆地的西南部和鄂尔多斯盆地西缘.这些研究成果展现了我国前寒武纪变质基底和具有一定规模的岩浆岩侵入岩体的深度变化特征,同时反映了沉积盖层的厚度和赋存现状,可直观了解各种类型的沉积盆地和沉积坳陷区的深度和范围,为寻找基底之上油气藏提供了直接依据.

Characteristics of China continent magnetic basement depth

The fluctuating characteristic of the metamorphosed basement of Precambrian era and the depth change of sedimentary cover are of great importance for geological structure study and energy and resources exploration. Some magnetic difference is present between the metamorphosed basement of Precambrian age and sedimentary cover, which permits geophysical study of magnetic basement depth using aeromagnetic data. This work is based on the magnetic basement depth data acquired by AGRS in the past more than 30 years, which has conducted aero geophysical surveys in China mainland, covering more than 30 basins and areas, and compiled the China's land magnetic basement depth map on the scale of 1:1000000 with transforming all the data into the same coordination system and scale. The study has revealed that using 105°E line as the boundary, the covers have large thickness in sedimentary depression areas of western China, and are mainly distributed in the Tarim basin, Junggar basin, Qaidam basin and Tibetan area. Meanwhile, in eastern China, mainly distributed in the Songliao basin, Erlian basin, Ordos basin, basin of southern part of North China, Sichuan basin, South Yellow Sea-Subei basin, the covers have relatively small thickness in sedimentary depression areas, whose largest thickness is located in the southwest of the Sichuan basin and the western edge of Ordos basin. These research achievements reveal the characteristics of the metamorphosed basement of Precambrian age and the depth change of irruptive rock bodies with certain scales, and reflect sedimentary covers' thickness and status. In terms of the achievements mentioned above, one can intuitively understand the depths and scopes of various types of sedimentary basins and sedimentary depression areas, which provide direct evidence for search for oil and gas reservoirs on the basements.