Sr, Nd isotope geochemistry of volcanic rock series and its geological significance in the middle Okinawa Trough |
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Authors: | MENG Xianwei CHEN Zhihua DU Dewen WU Jinlong |
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Institution: | 1. First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China;Key Laboratory of Marine Science and Numerical Modeling, State Oceanic Administration, Qingdao 266061, China 2. First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China |
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Abstract: | 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. |
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Keywords: | Okinawa Trough volcanic rocks Sr and Nd isotopes |
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