郯庐断裂带鲁苏皖段大地电磁测深剖面与地壳结构

Magnetotelluric depth sounding sections of Tan-Lu Fault Zone and its crustal structure in Shandong,Jiangsu and Anhui Provinces

近年来完成的穿过郯庐断裂带的4条大地电磁测深剖面,揭示了断裂带丰富的深部结构信息。郯庐断裂带已切穿了整个地壳,并且向下延入上地幔。该断裂带在深部显示为陡立的走滑构造,浅部为伸展断层及断陷盆地所叠加,最后又发生过一期明显的逆冲活动。在苏鲁造山带西缘,该断裂带早期呈现为典型的走滑构造,暗示造山期应为走滑构造起源。在该断裂带内部及其旁侧,浅部的断陷盆地发育并与深部的高导层(带)紧密伴生,反映断陷盆地发育时在深部都出现了软弱拆离带,也指示了断陷盆地发育中重要的深部过程。

Four MT depth sounding sections across the Tan-Lu Fault Zone show a lot of information about deep structure of the fault zone. The fault zone cuts cross the whole crust and extends into upper mantle. Vertical strike-slip structures are shown at the deep whereas the extensional faults and downfaulted basins occur at shallow levels. At the last stage of the evolution, clear thrusting was overprinted on the fault zone. The earlier structures on the western margin of the Jiangsu-Shandong orogenic belt are a result of strike-slip faulting,indicating that the fault was originated during the orogenic process. High-conductivity layers or zones at the deep are closely associated with the downfaulted basin at the shallow part in the fault zone and the vicinity areas. This demonstrates that formation of the down-faulted basins were associated with development of weak detachment zones at the deep, and the detachment slipping is an important deep process for the formation of the basins.