| Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa Trough) behind Ryukyu Arc：A review |
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| 作者姓名： | YAN Quanshu SHI Xuefa |
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| 作者单位： | Key Laboratory of Marine Sedimentary and Environmental Geology, the First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China;Key Laboratory of Marine Sedimentary and Environmental Geology, the First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China |
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| 基金项目： | The National Natural Science Foundation of China under contract Nos 41322036, 41230960, 40906034, 41276003 and 41176058; China Ocean Mineral Resources R&D Association (COMRA) under contract No. DY125-12-R-05. |
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| 摘 要： | 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 the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to 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 showed that several components were variably involved in the petrogenesis of the Okinawa Trough lavas: sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt(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 the primitive mantle wedge beneath the Ryukyu and subcontinental lithospheric mantle(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 the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the "seafloor spreading" process in the southwest segment, "rift propagation" process in the middle segment, and "crustal extension" process in the northeast segment, and a nascent ocean basin occurs in the southwest segment.
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| 关 键 词： | 边缘海盆地 冲绳海槽 琉球岛弧 构造演化 岩石学 大陆岩石圈地幔 菲律宾海板块 地球物理资料 |
| 收稿时间： | 2013/1/28 0:00:00 |
| 修稿时间： | 4/9/2013 12:00:00 AM |
Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa Trough) behind Ryukyu Arc: A review |
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| YAN Quanshu,SHI Xuefa.Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa Trough) behind Ryukyu Arc: A review[J].Acta Oceanologica Sinica,2014,33(4):1-12. |
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| Authors: | YAN Quanshu and SHI Xuefa |
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| Institution: | Key Laboratory of Marine Sedimentary and Environmental Geology, the First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China |
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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 the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to 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 showed that several components were variably involved in the petrogenesis of the Okinawa Trough lavas: sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt (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 the primitive mantle wedge beneath the Ryukyu and subcontinental lithospheric mantle (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 the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the "seafloor spreading" process in the southwest segment, "rift propagation" process in the middle segment, and "crustal extension" process in the northeast segment, and a nascent ocean basin occurs in the southwest segment. |
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| Keywords: | nascent ocean basin spreading tectonic evolution petrology geochemistry Okinawa Trough |
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