秦岭—大别造山带(湖北段)重力场特征与造山带构造

Gravity field characteristics and orogenic belt structure of the Qinling-Dabie orogenic belt(Hubei section)

利用区域重力资料,通过位场分离、转换技术,揭示了造山带深部构造特征。正的线状重磁异常带及各阶小波细节,清晰地反映了桐柏—大别及东秦岭造山带南缘缝合带的位置,特别是重力异常小波四阶逼近,深部构造特征更加醒目。在鄂西北地区岩石圈所呈现出的"立交桥式"双层结构中,自由空间、均衡重力、剩余重力异常及小波各阶细节明显地反映出相对浅部的造山带近东西向延伸的构造特征;各阶逼近结果则反映了相对深部的地壳-岩石圈地幔南北向伸展的构造特征。应用地球物理资料来研究地球岩石圈结构、构造,除深层地震外,区域重力也是最有效方法手段之一。特别是近年来二维小波变换技术日趋成熟,为应用区域重力资料解决诸如造山带深部构造等疑难问题提供了新的手段和工作思路。

On the basis of regional gravity data and through gravity anomaly separation and potential field transformation, the authors revealed the deep structural features of the orogenic belt. In this study, the authors found that the positive linear gravity and magnetic anomaly belt and the details of each order wavelet can clearly reflect the location of the suture belt at the southern edge ofthe Tongbai- Dabie and East Qinling orogenic belt. The fourth order approximation of the gravity anomaly wavelet can especially obviously reveal the deep structural features. In the＂overpass style＂ two- tier structure displayed in the lithosphere in northwest Hubei, the free space gravity, the isostatic gravity, the residual gravity anomaly and the wavelet details of each order can reflect the nearly EW-extending structural features of the relatively shallow orogenic belts clearly. Each order approximation result reflects the north-south stretching structural features of the relatively deep crust-lithosphere mantle. The analysis and study of the gravity field space form of the orogen belt are of important scientific and practical significance for the study of tectonic deformation of the central orogenic processes, the reconstruction of ancient suture position, the detection of the tectonic framework of the central orogenic belt and the recovery of the flatten process of the North China and South China Plates.