冲绳海槽的地质构造属性

ON THE GEOLOGIC NATURE OF OKINAWA TROUGH

冲绳海槽构造属性是地学界争论的问题之一,迄今已提出过断陷盆地、坳陷盆地、弧间盆地、弧后盆地、边缘海盆、张裂盆地等多种看法。本文作者在多次赴冲绳海槽调查和系统总结前人研究成果的基础上提出,冲绳海槽是一条现代活动裂谷,具有一系列典型的裂谷构造特征,其活动机制属于与洋壳俯冲作用有关的弧后裂谷。

The Okinawa Trough which lies at the east margin of the East China Sea has a lot of active structural features. This paper undertakes to understand the geological nature of the Okinawa Trough. Is Okinawa Trough a faulting-subsiding basin, depressed basin, mid-arc basin, back-arc basin, marginal sea, or an extending and rifting basin? Our geophysical and geological data show that the Okinawa Trough is a modern active rift valley as evidenced by the following characteristics: high heat flow (as high to 1 600 mW/m2), strong earthquake, large gravity anomaly (as much as 160mGal), more active volcanoes, rifting land-form, horizontal extension, thin crust, doming mantle, active fault,thin lithosphere, and so on. The origin and dynamics of the rifting is the subduction of the Philippine plate under Ryukyu arc. The Okinawa Trough is now an active back-arc rift developed in the west margin of the Pacific Ocean and has relation with the plate subduction. Its rifting time may be from Pliocene to. now.