冲绳海槽弧后张裂构造及其动力机制讨论

Discussion on back-arc rifting tectonics and its geodynamic regime of the Okinawa Trough

在总结、讨论冲绳海槽弧后张裂构造的地形地貌、地球物理场和动力背景特征的基础上,归纳出海槽北、中、南三段之间的差异,以及它们在陆坡、槽底、岛坡上的不同表现特征.槽底雁行排列的地堑及断层斜切入陆坡,伴随的断块隆脊作用往南加强,使得钓鱼岛—赤尾屿隆起带区别于其北边的陆架外缘隆起带,吕宋岛向台湾的碰撞挤压引起的旋张活动加强了海槽南段的地壳拉张,从北往南岛坡侧都可以追踪出双列岛弧特性.海槽内部构造现象不能为笼统的构造动力背景所能完全解释,需要对各个典型中央地堑的具体深入探测研究.鉴于地堑、地垒、断层以及它们所界定的构造单元和它们内部发生的岩浆作用各有特点,最后讨论了各个地段中央地堑的构造属性、动力要素的差异及变化规律,以期为海槽构造动力的进一步深入研究提供借鉴参考.

Topographic relief, gravity anomalies, magnetic anomalies and geodynamic regime are pertinently discussed for back-arc rifting tectonics of the Okinawa Trough. They are of different characteristics along the continental slope＇s trough bottom and island slope, respectively, among the northern, middle and southern trough. En echelon grabens or faults on the trough bottom cut obliquely into the continental slope, accompanying with block ridge rifting intensively southwards. In the southern trough, the Diaoyu Island-Chiwei Islet uplift has got rid of features borne by the continental shelf edge uplift to its north, while rotational rifting driven by collision between Luzon and Taiwan has enhanced the crustal extension. Nevertheless, the inner volcanic arc can be traced to Taiwan along the island slope. Different tectonic features can hardly be interpreted only by a general geodynamic background, and there is a large room of research and study for various grabens typical of the trough. Based on different features indicated by grabens, horsts, faults and their delineating tectonic units, together with diverse magmatism, differences and originations of both tectonic attributes and geodynamic factors are mainly explored for these tectonic structures, aiming at further deepening into research of tectonics and geodynamics of the Okinawa Trough.