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| Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa trough) behind Ryukyu arc: a review |
| 琉球岛弧后的一个初生洋盆（冲绳海槽）的构造演化的岩石学证据 |
| Received:January 28, 2013 Revised:April 09, 2013 |
| DOI：doi: 10.1007/s13131-014-0400-2 |
| Key words:Rifting, Spreading, Tectonic evolution, Petrology and Geochemistry, Okinawa trough |
| 中文关键词: 裂解作用，扩张作用，构造演化，岩石学和地球化学，冲绳海槽 |
| 基金项目:国家自然科学基金项目（面上项目，重点项目，重大项目） |
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| Abstract: |
| Okinawa trough is a back-arc, initial marginal sea basin, located behind the Ryukyu arc-trench system. The formation and evolution of the Okinawa trough is intimately related to the subduction process of the Philippine Sea plate beneath Eurasian Plate since late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, e. g., Mariana trough, the southern Lau basin, and all of them are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from Okinawa trough, Ryukyu arc and Philippine Sea plate being subducted, combined with geophysical data, indicate the relationship between the subduction sources (input) and arc or back-arc magmas (output) in the Philippine Sea plate-Ryukyu arc- Okinawa trough system (PROS). The results obtained shows that several components variably involved in the petrogenesis of the Okinawa trough lavas, i.e., sub-continental lithospheric mantle underlying Eurasian plate, Indian MORB-type mantle and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies primitive mantle wedge beneath the Ryukyu and SCLM beneath the Okinawa trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates magma source. Along the strike of the Ryukyu arc and the Okinawa trough, the systematically variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. |
| 中文摘要: |
| 冲绳海槽是位于琉球弧-沟系统之后的一个弧后的、初始边缘海盆。冲绳海槽的形成和演化与自晚中新世以来菲律宾海板块俯冲于欧亚板块之下的过程紧密相关。本海槽的构造演化类似于其他活动的弧后，如马里亚纳海槽、劳海盆南段，它们都正在经历初始裂解作用并伴随随后的海底扩张过程。本研究评述了冲绳海槽、琉球岛弧及正在俯冲的菲律宾海板块的镁铁质火山熔岩的岩石学和地球化学资料，结合地球物理学资料，揭示了在菲律宾海板块-琉球弧-冲绳海槽系统（PROS）内俯冲源（输入）与弧或弧后岩浆（喷出）之间的关系。所获得的结果显示，以下几个组分多变地参与进了冲绳海槽熔岩的岩石成因中，即下伏于欧亚板块的大陆底岩石圈地幔（SCLM）、印度洋MORB型地幔以及太平洋MORB型地幔。来自具印度洋MORB型地幔特征的俯冲组分在浅水平释放的含水流体和在深位释放的含水熔体，已经加入到熔岩的地幔源区内，从而多变地修改了琉球弧之下的原始地幔楔以及冲绳海槽之下的大陆底岩石圈地幔。在海槽和弧的东北端，太平洋MORB型地幔（而不是印度洋MORB型地幔）在岩浆源区内占统治地位。沿着琉球岛弧和冲绳海槽走向，微量元素比值和同位素组分的系统变化反映了多变俯冲组分输入对岩浆源区的第一序的影响。 |
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