The Jizhong Depression is located in the northwest of Bohai Bay Basin, with the Paleogene syn-rifting magmatic and volcanic activities widely developed. With drilling and three-dimensional seismic data, we investigate the magmatic activities in the Langgu Sag and the Wen´an Slope in the north of Jizhong Depression by means of profile interpretation and RMS Amplitude attribute extraction. The results show that igneous rocks of Es4 are mainly developed in the Langgu Sag, with basalt, diabase and tuff found by drilling, as well as large number of dykes recognized on profile. The Wenan slope yields igneous rocks of mainly Es3, with basalt and tuff, as well as a small amount of diabase revealed by drilling, but barely any dykes recognized on profile. We conclude that the fault geometry in rift basin is an important factor controlling the type of magmatic and volcanic activities. In the Langgu Sag, there are no high?angle large?scale faults developed that penetrates strata layers vertically to become magma channels. As a result, magma was migrated upward dispersedly through a large number of dykes to the surface and accumulated in circular shapes, resembling to the features of central eruption. High-angle normal faults penetrating strata layers are developed in the Wen´an Slope, therefore, through these faults the vast majority of magma is migrated upward to the surface along major faults and accumulated linearly, resembling to the features of fracture eruption. Our analysis suggests the existence of high?angle faults that cut through strata layers is an important factor controlling the occurrence of different types of magmatic activities in rift basins.
Mao Liguang Yang Dexiang Li Xiaoheng Zhang Chuanbao Tian Jianzhang Wang Xin Ming Jin Xiao Ancheng. Characteristics and controlling factors of the Paleogene magmatic activities in the northern Jizhong Depression[J]. Chinese Journal of Geology, 2020, 55(2): 506-518.