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    Petrologic perspectives on tectonic evolution of a nascent basin (Okinawa trough) behind Ryukyu arc: a review
    琉球島弧后的一個初生洋盆(沖繩海槽)的構造演化的巖石學證據
    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
    中文關鍵詞:  裂解作用,擴張作用,構造演化,巖石學和地球化學,沖繩海槽
    基金項目:國家自然科學基金項目(面上項目,重點項目,重大項目)
    Author NameAffiliationAddress
    yan quanshu 國家海洋局第一海洋研究所 青島高科園仙霞嶺路6號 海洋一所地質室
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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:
          沖繩海槽是位于琉球弧-溝系統之后的一個弧后的、初始邊緣海盆。沖繩海槽的形成和演化與自晚中新世以來菲律賓海板塊俯沖于歐亞板塊之下的過程緊密相關。本海槽的構造演化類似于其他活動的弧后,如馬里亞納海槽、勞海盆南段,它們都正在經歷初始裂解作用并伴隨隨后的海底擴張過程。本研究評述了沖繩海槽、琉球島弧及正在俯沖的菲律賓海板塊的鎂鐵質火山熔巖的巖石學和地球化學資料,結合地球物理學資料,揭示了在菲律賓海板塊-琉球弧-沖繩海槽系統(PROS)內俯沖源(輸入)與弧或弧后巖漿(噴出)之間的關系。所獲得的結果顯示,以下幾個組分多變地參與進了沖繩海槽熔巖的巖石成因中,即下伏于歐亞板塊的大陸底巖石圈地幔(SCLM)、印度洋MORB型地幔以及太平洋MORB型地幔。來自具印度洋MORB型地幔特征的俯沖組分在淺水平釋放的含水流體和在深位釋放的含水熔體,已經加入到熔巖的地幔源區內,從而多變地修改了琉球弧之下的原始地幔楔以及沖繩海槽之下的大陸底巖石圈地幔。在海槽和弧的東北端,太平洋MORB型地幔(而不是印度洋MORB型地幔)在巖漿源區內占統治地位。沿著琉球島弧和沖繩海槽走向,微量元素比值和同位素組分的系統變化反映了多變俯沖組分輸入對巖漿源區的第一序的影響。
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