应用地球物理资料对胶南地体构造特征的探讨

A DISCUSSION ON THE STRUCTURAL FEATURES OF THE JIAONAN TERRAIN BASED ON THE GEOPHYSICAL DATA

本文根据新的地球物理资料和地体构造的研究成果,探讨了胶南地体构造的深部特征和依据。胶南地体处在华北地台与扬子地台之间构造缝合带上,它应为秦岭造山带越过郯庐断裂的向东延伸部分;五荣断裂为其北界,赣榆黄海断裂为南界。胶南地体可能是在秦岭造山过程中两大板块碰撞增生形成。胶南重力低不仅与地幔低凹有关,而且与该地体内广泛发育的密度较小的花岗岩类岩石及低密度值的元古界胶南群内混合岩、片麻岩、变粒岩等岩石密切相关。

The authors expounded the features of the deep structures in the Jiaonan terrain based on the new geophysical data and the results obtained from a study on the terrain structures.The Jiaonan terrain is situated on the suture zone between the North China Platform and the Yangtz Platform and should be an east extension of the Qinling orogenic belt passing through the Tancheng- Lujiang fracture zone.The Wulian-Rongcheng fault is the northern boundary and the Ganyu- Huanghai fault is the southern boundary of the Jiaonan Terrain which thus was probably formed by the collision-accretion of the two plates during the course of the Qinling Orogeny.The gravity low in the Jiaonan terrain is related not only to the depression of the mantle,but also more closely to such roeks as granitoids of low density which are widespread in the terrain and as migmatites,gneisses and leptynites of the Proterozoic Jiaonan group which have low densities as well.