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Arc‐type and intraplate‐type ridge basalts formed at the trench‐trench‐ridge tripIe junction: Implication for the extensive sub‐ridge mantle heterogeneity
Author(s) -
Osozawa Soichi,
Yoshida Takeyoshi
Publication year - 1997
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/j.1440-1738.1997.tb00170.x
Subject(s) - basalt , geology , mantle (geology) , magmatism , triple junction , ridge , silicic , geochemistry , intraplate earthquake , trench , island arc , subduction , petrology , seismology , paleontology , tectonics , geophysics , materials science , layer (electronics) , composite material
‘ In situ basalts’ represent the ridge magmatism at and close to the ancient trench‐trench‐ridge triple junction. Such basalts in the Amami, Mugi, and Setogawa accretionary complexes, Southwest Japan, were described and analysed. The geochemical data show that the ‘ in situ basalts’ include all the types of basalts, ranging from alkali basalts and high‐alumina basalts to tholeiites, and the compositions tend towards intermediate and silicic rocks. The data also reveal that the ridge basalts are indistinguishable both from the island arc and intraplate basalts, no affinities with mid‐ocean‐ridge basalts. The sub‐ridge mantle adjacent to the triple junction had a component of sub‐arc mantle, and this mantle heterogeneity can be generated by the formation of a slab window.