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东海冲绳海槽,位于琉球岛弧-海沟系的陆侧,为半深海弧后边缘地.近年来,国内外学者作了一系列实际调查和专门研究,极大地促进了对海槽地壳演化的认识.但在探讨海槽深部构造时,均未论证异常地幔的存在;在剖析槽底地壳性质时,认为已出现新生洋壳或认为属过渡型地壳,分歧存疑之处颇多.在板块大地构造框架中,普遍认为边缘盆地是弧后扩张(形成新洋壳)的产物,但在冲绳海槽,地壳厚度明显大于正常洋壳,拖网取样采获大量中酸性岩石,从而对海槽的扩张成因产生了种种疑问.本文将在前人工作基础上,试就上述问题展开讨论,进而确定冲绳海槽在洋盆演化阶段中的特殊位置.
The Okinawa Trough in the East China Sea, located on the land side of the Okinawa arc-trench system, is the margin of the semi-deep marine arc. In recent years, domestic and foreign scholars made a series of practical investigations and special studies that greatly promoted the evolution of the crust However, when discussing the deep structure of the trough, neither of them demonstrates the existence of anomalous mantle. When analyzing the crustal properties at the bottom of the trough, it is considered that there are many new drowned or considered transitional crustalities, In the framework of the tectonic framework, it is generally considered that the marginal basin is the product of back-arc expansion (forming a new oceanic crust). However, in the Okinawa Trough, the thickness of the crust is obviously larger than that of the normal oceanic crust, and a large amount of moderate- This paper will try to discuss the above issues on the basis of previous work, and then to determine the special position of the Okinawa Trough in the evolutionary stage of the ocean basin.