冲绳海槽及邻区磁异常特征及其地质解释

Magnetic anomaly pattern and interpretation of the Okinawa Trough and adjacent areas

对冲绳海槽及邻区的ΔT磁异常特征进行了定性分析和变纬度化极处理,通过对比ΔT磁异常和化极磁异常分布特征,对冲绳海槽及邻区几个构造地质学问题进行了探讨。冲绳海槽基底埋深较大,沉积中心位于海槽西部;钓鱼岛隆褶带大规模基底隆起的南端终止于渔山-久米断裂带,断裂带以南的东海陆架南部边缘覆盖了厚层沉积物;以渔山-久米断裂带、舟山-国头断裂带和吐噶喇断裂带为代表的NW-NWW向右旋平移断裂带在东海构造演化过程中自西向东逐渐前展,对构造应力场起到了重要的调节作用,是东海"南北分块"构造格局中主要的构造单元边界;中新世以来台湾碰撞造山作用引起了东海陆架南部主要构造单元的顺时针旋转;菲律宾海板块的俯冲对琉球弧前地区的磁异常分布产生了显著影响。

In this study, we applied pole-reduction calculations with varied declinations and inclinations to the total magnetic anomaly of the Okinawa Trough and adjacent areas to obtain the pole magnetic anomaly. In a comparison and correlation of the AT and pole magnetic anomalies, we examined several tectonic problems of the study areas. The results show that the basement of the Okinawa Trough is buried deeply and the depocenter is located in the western part of the trough. The large-scale basement uplift of the Diaoyudao belt terminates in the south by the Yu- shan-Kume fault belt. The shelf edge area south of the Yushan-Kume fault belt is covered by thick sediments. The NW-NWW trending dextral strike-slip faults are represented by the Yushan-Kume fault, the Zhoushan-Kunigami fault, and the Tokara fault, which have propagated southeastward during the tectonic evolution history of the East China Sea, then transferred the tectonic stress field and formed the main boundaries of the blocked tectonic frame- work from the south to the north. Induced by the Taiwan collision process, the tectonic trends of the southwestern part of the shelf have rotated clockwise. The magnetic anomaly patterns of the arc and forearc areas are influenced by the subducting Philippine slab.