Geochemistry of high Mg andesites and the tectonic evolution of the Okinawa Trough–Ryukyu arc system
書誌事項
- 公開日
- 1999-05
- 権利情報
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- https://www.elsevier.com/tdm/userlicense/1.0/
- DOI
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- 10.1016/s0009-2541(98)00199-5
- 公開者
- Elsevier BV
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説明
Abstract Mineral chemistry, major- and trace-elements, and Sr–Nd isotopic compositions of high magnesian andesites and basalt from the central and southern Ryukyu arc, Japan, provide insight into the nature of the mantle wedge and reflect the magmatic evolution of the Okinawa Trough back-arc basin. The high-Mg andesites and basalts (∼6 Ma) from the central Ryukyu islands exhibit enrichment of large-ion-lithophile elements (LILE) relative to high-field-strength elements (HFSE), typical of subduction-related lavas. These rocks are distinct in having low 87 Sr / 86 Sr (0.7033–0.7035) and high 143 Nd / 144 Nd (0.5129–0.5130) relative to the contemporaneously erupted calc-alkaline rocks in the region and the Okinawa Trough basalts. High-Mg andesites from Central Ryukyu are similar to adakitic high-Mg andesites, except for their low La/Yb (∼6) compared to that of adakites (>20). The combination of passive asthenospheric upwelling, induced by mid to late Miocene rifting of the Okinawa Trough, and a thermal rebound due to a ∼10–6 Ma subduction hiatus of the Philippine Sea Plate, probably resulted in a high geothermal gradient beneath the arc that eventually caused partial melting of the subducted slab. Subsequent interaction of the slab-melts with the overlying mantle wedge produced adakite-like high-Mg andesites at shallow level (
収録刊行物
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- Chemical Geology
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Chemical Geology 157 (1-2), 69-88, 1999-05
Elsevier BV
