Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge,the middle Okinawa Trough：implications for petrogenesis and a mantle source  

作　　者：LI Xiaohui ZENG Zhigang CHEN Shuai MA Yao YANG Huixin ZHANG Yuxiang CHEN Zuxing 

机构地区：[1]Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China [2]University of Chinese Academy of Sciences, Beijing 100049, China [3]Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China

出　　处：《Acta Oceanologica Sinica》2018年第1期73-88,共16页海洋学报（英文版）

基　　金：The National Basic Research Program(973 Program)of China under contract No.2013CB429700;the National Natural Science Foundation of China under contract Nos 41325021 and 41706052;the National Program on Global Change and AirSea Interaction under contract No.GASI-GEOGE-02;the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030302;the Special Fund for the Taishan Scholar Program of Shandong Province under contract No.ts201511061;the AoShan Talents Program supported by Qingdao National Laboratory for Marine Science and Technology under contract No.2015ASTP-0S17;the Innovative Talent Promotion Program under contract No.2012RA2191;the Science and Technology Development Program of Shandong Province under contract No.2013GRC31502;the Scientific and Technological Innovation Project Financially supported by Qingdao National Laboratory for Marine Science and Technology under contract Nos 2015ASKJ03 and2016ASKJ13;the National High Level Talent Special Support Program;the CAS/SAFEA International Partnership Program for Creative Research Teams;Qingdao Collaborative Innovation Center of Marine Science and Technology

摘　　要：As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge（IR）, the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr（0.703 862–0.704 884）, ^144Nd/^143Nd（0.512 763–0.512 880） and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle（DM） but extends to the enriched mantle（EMII）, indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge（IR）, the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr（0.703 862–0.704 884）, ^144Nd/^143Nd（0.512 763–0.512 880） and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle（DM） but extends to the enriched mantle（EMII）, indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.

关 键 词：basic to intermediate-acid rocks fractional crystallization subduction sediment components Iheya Ridge Okinawa Trough 

分 类 号：P4[天文地球—大气科学及气象学]