重磁资料揭示的冲绳海槽及邻区断裂和岩浆岩分布
FAULT BELTS AND IGNEOUS ROCKS OF THE OKINAWA TROUGH AND ADJACENT AREAS:EVIDENCE FROM GRAVITY AND MAGNETIC DATA
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摘要: 冲绳海槽及邻区是强烈的构造活动区,断裂和岩浆岩分布广泛。以1:100万重磁数据为基础,计算了空间重力异常、布格重力异常和ΔT磁异常的垂向和水平方向一阶和二阶导数,通过对比计算结果,对冲绳海槽及邻区断裂和岩浆岩分布特征进行了研究。结果表明,冲绳海槽发育平行和垂直于海槽走向的两组断裂带,其中垂直于海槽走向的NW、NWW向断裂带为走滑断裂,在东海构造演化过程中长期发育并逐渐向东前展,受不同时期构造应力场变化的影响,走向自西向东发生变化,整体呈现NE向凸出的弧形;岩浆岩呈带状分布,海槽东侧自北向南纵贯海槽的岩浆岩带与琉球火山前锋相对应;与钓鱼岛隆褶带相对应的宽阔岩浆岩带南端终止于27°N的NW向断裂带附近;海槽南段轴部岩浆岩带与海槽现今的扩张活动有关,而陆架边缘和陆坡上部的台北-钓鱼岛火山岩带的构造属性不同于北部的钓鱼岛隆褶带。Abstract: The Okinawa Trough is an active tectonic area with widespread faults and igneous rock bodies. In order to study the characteristics of the fault belts and igneous rocks, we calculated the vertical and horizontal derivatives of gravity and magnetic anomalies on 1:1000000 scale. The results show that there are two groups of fault belts distributed in the Trough and adjacent areas, running parallel and perpendicular to the trough, respectively. The NW and NWW trending fault belts, which are perpendicular to the trough itself, are mainly strike-slip faults, formed in earlier time and gradually propagated southeastward together with the tectonic evolution of the East China Sea. Influenced by the tectonic stress fields in different periods, the strike of the fault belts changed from west to east, making the fault belts bulged northeastward. The igneous rocks are distributed in several belts. The belt located in the eastern side of the trough, which extends from Kyushu to Taiwan, is corresponding to the Ryukyu volcanic front. Another belt located on the eastern margin of the shelf, which corresponds to the Diaoyudao uplift, terminates to the south by one of the NW trending fault belts near 27°N. The Igneous rock belt located in the axial part of the southern Okinawa Trough is related to the rifting process. The tectonic nature of the Taibei-Diaoyudao volcanic belt is different from the Diaoyudao uplift to the north.