Sr, Nd isotope geochemistry of volcanic rock series and its geological significance in the middle Okinawa Trough  

作　　者：孟宪伟 陈志华 杜德文 吴金龙 

机构地区：[1]First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China [2]Key Laboratory of Marine Science and Numerical Modeling, State Oceanic Administration, Qingdao 266061, China

出　　处：《Science China Earth Sciences》2000年第5期458-463,共6页中国科学（地球科学英文版）

摘　　要：There exists extensive basic-acidic volcanic rock series in the middle section of the Okinawa Trough. Different types of these volcanic rocks have their own average strontium ratios of 0.704 749, 0.705 062, 0.708 771, 0.704 840 and 0.720 301 with average143Nd/144Nd ratios of 0.512 820, 0.512 673, 0.512 413, 0.512 729 and 0.512 034. These ratios of Sr and Nd isotopes all fall on a theoretic hyperbolic curve of mixing between two end-members of MORB and rhyolitic magma. So we infer that these different kinds of volcanic rocks in the middle Okinawa Trough are the erupted product in different stages of formation and evolution of the trough crust. MORB magma, which had suffered assimilation, mixed with the early-formed crust-derived rhyolitic partial melt mass at different ratios; then, these mixed magma erupted and formed volcanic rock types of the trough. This study indicates that the Okinawa Trough is coming into a stage of submarine spreading from the stage of continental rift.There exists extensive basic-acidic volcanic rock series in the middle section of the Okinawa Trough. Different types of these volcanic rocks have their own average strontium ratios of 0.704749, 0.705062, 0.708771, 0.704840 and 0.720301 with average 143Nd/144Nd ratios of 0.512 820, 0.512 673, 0.512 413, 0.512 729 and 0.512 034. These ratios of Sr and Nd isotopes all fall on a theoretic hyperbolic curve of mixing between two end-members of MORE and rhyolitic magma. So we infer that these different kinds of volcanic rocks in the middle Okinawa Trough are the erupted product in different stages of formation and evolution of the trough crust. MORE magma, which had suffered assimilation, mixed with the early-formed crust-derived rhyolitic partial melt mass at different ratios; then, these mixed magma erupted and formed volcanic rock types of the trough. This study indicates that the Okinawa Trough is coming into a stage of submarine spreading from the stage of continental rift.

关 键 词：OKINAWA TROUGH VOLCANIC rocks SR and Nd isotopes. 

分 类 号：P597[天文地球—地球化学]