关键词: 大地电磁, 东南沿海地区, 电性结构, 壳幔结构, 动力学, 岩石圈

Abstract:

Four magnetotelluric sounding profiles were designed and relevant 2D electrical structure models were obtained in order to research the electrical structure of crust-mantle in southeast coastal region of South China.These electrical structures combined with geological background and geochemical information reveal that the west part of crust in this area became thicker because of the collision and aggregate effect, while the thickness of east section decreased rapidly due to Pacific plate subduction. The lithosphere structure in southeast coastal region of China does not simply have “west thick and east thin”feature. Lithosphere thicknesses at two ends of research area exceed 100 km. It is speculated that the thickness increeasing in western end is due to intracontinental compression orogeny or intracontinental collision and convergence orogeny,the thickness changes in east section may be the result of the oceanic crust retentions under the lithosphere when the period of oceanic plate subduction or the Pacific ancient land mass retentions under the lithosphere. The lithosphere gets thiner in central part may relates to the intrusion of asthenospheric material. The power of upper intrusion of asthenospheric material in large scale came from deep thermal disturbance formed by Pacific plate subduction.

Key words: magnetotellurics, southeast coastal region, electrical structure, crust-mantle structure, dynamics, lithosphere