郯庐断裂带南段的重磁场特征及其地质意义

Gravity and magnetic anomaly in the southern Tanlu fault zone and its geological interpretation

由于断裂两侧的磁性、密度的纵横向差异在重力、磁力异常上有所表现,因此所获得的重力、磁力数据为深入研究关键的地质课题提供了科学基础,如郯庐断裂带的基底性质、断裂形成特征和岩浆岩分布。利用最新的高精度航空重力和磁力数据以及地面重力数据,绘制了郯庐断裂带地区的1∶50 000重力和磁力异常图,并结合区域地质数据分析了重力和磁力异常特征。分析结果认为:存在连体的郯庐—大别古老构造带,郯庐断裂带南段是元古宙和燕山中期岩浆活动的复合反映带;郯庐断裂带为中元古—新元古代时期南华北陆块与下扬子陆块的界限;磁力、重力异常图对比说明,合肥盆地范围由老到新向东扩展。

The differences between transverse and longitudinal magnetism or density on both sides of a fault are reflected in gravity and magnetic anomalies. Therefore, the gravity and magnetic anomaly data provide a scientific basis for in-depth studies of key geological research topics, such as the base properties, fault formation characteristics and magma distribution in the Tanlu fault zone. The 1∶50000 scale gravity and magnetic anomaly maps of the Tanlu fault zone were drawn using the up-to-date high-precision airborne gravity data, aeromagnetic data and ground gravity data. Combined with the regional geological data, the characteristics of gravity and magnetic anomalies were also analyzed. The results indicated the existence of an ancient conjoined Tanlu-Dabie structural belt, where the southern segment of the Tanlu fault zone reflects the magmatic activities in the Proterozoic-Middle Yanshan period, while the entire fault zone defines the boundary between the southern North China block and the Yangtze block in the Mesoproterozoic-Neoproterozoic era. A comparison of the magnetic and gravity anomaly maps showed an eastward expansion of the Hefei Basin over geological time.