摘要
根据1990年以来对冲绳海槽地质地球物理调查的最新实测资料，包括多道和单道反射地震、海底地震仪折射地震、重磁测量、水深测量、海底岩石拖网，结合国内外学者对冲绳海槽的调查研究成果，对冲绳海槽地壳结构进行了探讨，得出如下初步结论：（1）冲绳海槽是一个典型的发育在大陆地壳边缘、由陆壳张裂而成、处于裂谷作用最高演化阶段、洋壳即将产生、海底扩张即将出现的弧后活动裂谷。（2）根据火成岩发育、沉积层分布和地壳结构分析，冲绳海槽尚缺少已经开始“扩张”的证据，还不能确定海槽中央已经发育了大洋地壳。冲绳海槽目前仍属于拉薄的大陆地壳。（3）冲绳海槽作为一个浅海槽状地貌单元，形成于距今6Ma。作为一个弧后裂谷，自距今2Ma以来开始强烈的张裂活动。海槽中央张裂地堑（槽中槽）距今2Ma以来开始形成并逐渐发展。中央张裂地堑内的火成岩年龄不大于1Ma。因此，冲绳海槽是一个年青的、正在活动的弧后裂谷盆地。
<Abstrsct> The Okinawa Trough which lies at the southastem margin of the East China Sea,is an astive back-are rift and a part of the Ryukyu T-A-BA system. Many geological and geophysical studies have shown that the Okinawa Trough is associated with an extremely high heat flow,strong submarine hydrothermal activities,frequent earthquaks,strong volcanic eruptions, well-developed central grabens and active faults,and a thin crust and lithosphere. Up to now, the crustal nature of the Trough is still a key debating question.Based on the new geological and geophysical data collected since 1990,includ ing, single and multiple channel seismic reflections, ocean bottom seismometer (OBS) refractions, gravity and geomagnetic measurements,water depth sounding,submarine sampling and sea bottom dragging,the authors have undraken analyses of the crustal structure of the Okinawa Trough. The conclusions obtained in this study are listed below.1. Except the Andaman Sea with a complex oblique opening,the Okinawa Trough is the ouly example in the world of an active marginal back-arc rift opening along a continental boundary; it is formed by continental crustal extension,at a special high evoluting stage of a back-are rift,near the end of a rifting period and the beginning of a spread. Hence the Okinawa Trough is tectonicly a modern active rift valley.2. Analyses of igneous rock distribution patterns,sediment thickness and crustal structures,show that there is no oceanic crust in the central graben of the Trough and the Okinawa Trough has not begun to 'spread' till now. The crust of the Trough is still continental in character because of the continental extension.3. Based on an seismic profile interpretation,the K-Ar dating for igneous rock sampes and heat flow calculations,as a submarine 'Trough',the Okinawa Trough was formed 6 Ma B. P.; however,as a back-arc rift 4. The Okinawa Trough is a typical astive zone in the marginal area of the westem Pacific. The study on its crust nature and tectonic astivity is of great significance for
出处
《海洋与湖沼》
CAS
CSCD
北大核心
1998年第4期441-450,共10页
Oceanologia Et Limnologia Sinica
基金
中国科学院院长基金!211950257
关键词
冲绳海槽
地壳结构
中央地堑
地质构造
Okinawa Trough
Crustal structure Central graben
Geological structure
