THE DEEP GEOELECTRICAL CHARACTERISTICS IN DAZU, SICHUAN-QUANZHOU, FUJIAN
JIANG HONG-KAN(The Central Laboratory of Petroleum Geology, Ministry of Geology & Mineral Resources, Wuxi 214151)ZHAN SHUANG-QING WANG HONG-XUN(No. 1 Exploration Geophysics Research Party, Ministry of Geology & Mineral Resources, Bengbu 233005)
According to the data from the magnetotelluric sounding profile from Dazu, Sichuan to Quanzhou, Fujian, the low resistivity Mesozoic-Cenozoic, the high resistivity Triassic-Paleozoic and the relative low resistivity Banxi Group of the Proterozoic in low grade metamorphism have been distinguished. The depth of the bottom boundaries for some rock mass are estimated. It can be predicted that the swarm of dikes occur in the depth below 5km in the Yuanma basin.The resistivity from the middle-lower crust to the upper mantle of lithosphere, near the gravity gradient zone in the Wuling mountain, is very high. It is related to the forming of the gradient zone. The high conductivity layer in the crust widely occurs in the Southern China fold system. Its location is near the low velocity layer in the crust .from the explosion seismic data.Based upon the deep geoelectrical characters, the Huaying Shan fault zone, the dialing fault zone and the Fuan-Nanjing fault zone and some other zones are recognized as deep and large fault zones.The resistivity in the upper mantle of the lithosphere along the profile is different. From the west to east, the depth of the asthenosphere varies from 120-150km to 76km. The deepest is 240km in the east to Hengyang.According to the variation of the asthenosphere and the distribution of the fault system, it is suggested that the border between the Yangtze paraplatform and the Southern China fold system is near the Chaling-Yongxing fault zone.