Abstract: Measured on the basis of four high-precision gravity and magnetic profiles and the MT profiles, combined with regional geological data and field geological research, the deep-seated geological issues of the Liaoji Paleoproterozoic rift, such as the boundaries, the internal geological structure and the substrate composition, are discussed. The newly acquired non-seismic geophysical profile data provide important information for revealing the deep geological structure of the Liaoji rift. It is found along the MT inversion profile that a clear south-dipping structure interface exists in the area of Lianshanguan-Saima, which is an extensional fault surface that controls the northern boundary of Liaoji rift. In the past, the line of Benxi city-Benxi county, where the northern boundary of Liaohe Group is distributed, was considered to be the ancient geographical boundary of Liaoji rift. It is confirmed that the difference between lithofacies of the north and south Liaohe Group is caused mainly by phase transition. MT inversion profiles reveal that the interior of the Liaoji rift is characterized by double-fold structure, with the basement depth reaching over 10km. Regional geological studies and joint gravity-magnetic-electric inversion results show that two types of basement are developed beneath Liaoji rift: (1)Archean supracrustal rocks-granite, and(2)Archean granite-Proterozoic granite.

Key words: Liaoji rift, boundary property, internal structure, basement composition

摘要： 在4条实测高精度重、磁剖面及MT剖面探测的基础上，结合区域地质资料及野外地质研究，对辽吉古元古代裂谷（简称辽吉裂谷）边界、内部地质结构和基底组成等深部地质问题进行了论述。 新获取的非震地球物理剖面为揭示辽吉裂谷的深部地质结构提供了重要信息，在MT剖面上发现沿连山关—赛马一线存在一个明显的南倾构造界面，该界面为控制辽吉裂谷北部边界的伸展断裂构造面，以往认为在本溪市—本溪县一线辽河群分布的北部边界应为辽吉裂谷的古地理边界；证实南北辽河群岩相的差异主要是由相变造成的；MT剖面揭示出辽吉裂谷内部具有复式褶皱结构特征，基底埋深可达10km以上；区域地质研究及重磁电联合反演结果表明辽吉裂谷的基底主要发育2种类型：一是太古代表壳岩花岗岩型；二是太古代花岗岩-古元古代花岗岩型。

关键词: 辽吉裂谷, 边界性质, 内部结构, 基底组成