Sr, Nd isotope geochemistry of volcanic rock series and its geological significance in the middle Okinawa Trough
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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.
KeywordsOkinawa Trough volcanic rocks Sr and Nd isotopes
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- 1.Ishizuka, H., Kawanobe, Y., Sakai, H., Petrology and geochemistry of volcanic rocks dredged from the Okinawa Trough, an active back-arc basin, Geochemical Journal, 1990, 24: 75.Google Scholar
- 2.Chen Lirong, Zhai Shikui, Shen Shunxi, Isotopic characteristics of pumice and its age dating in the Okinawa Trough, Science in China (in Chinese), Ser. B, 1993, 23(3): 324.Google Scholar
- 3.Li Weiran, Yang Zuosheng, Zhang Baoming et al., Study of olive tholeiite in the southern Okinawa Trough, Oceanologia et Limnologia Sinica (in Chinese), 1997, 28(6): 665.Google Scholar
- 4.Qin Yunshan, Zhai Shikui, Mao Xueying et al., REE characteristics of pumice and its geological significance in the Okinawa Trough, Oceanologia et Limnologia Sinica (in Chinese), 1987, 18(4): 313.Google Scholar
- 5.Zhai Shikui, Gan Xiaoqun, Mineralogy and petrology of basalt and their geological significance in a hydrothermal activity area of the Okinawa Trough, Oceanologia et Limnologia Sinica (in Chinese), 1995, 26(2): 115.Google Scholar
- 6.Qiu Jiaxiang, Volcanic Petrology, Beijing: Geology Press, 1985, 207–220.Google Scholar
- 7.Zhang Zongqing, Ye Xiaojiang, Methods of ICP-MS analysis of rare earth elements and accurate measurement of143Nd/144Nd ratios, Journal of Institute of Geology, Chinese Academy of Sciences, 1987, 17: 105.Google Scholar
- 9.Claude, J. A., Bruno, H., Ariel, P. et al., Topology in isotopic multispace and origin of mantle chemical heterogeneities, Earth and Planetary Science Letters, 1986/1987, 81: 319.Google Scholar
- 11.Faure, G., Principle of Isotope Geology, New York: Wiley, 1986, 117–247.Google Scholar