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A contribution of slab‐melts to the formation of high‐Mg andesite magmas; Hf isotopic evidence from SW Japan
Author(s) -
Hanyu Takeshi,
Tatsumi Yoshiyuki,
Nakai Shun'ichi
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl015856
Subject(s) - andesites , basalt , geology , andesite , geochemistry , subduction , slab , magma , metasomatism , isotope , mantle wedge , petrogenesis , volcanic rock , volcano , petrology , mantle (geology) , tectonics , geophysics , seismology , physics , quantum mechanics
Hf isotope ratios were measured for high‐Mg andesites (HMA) and basalts from the Setouchi volcanic belt, Southwest Japan, in order to examine whether fluid or melt from subducted slabs act as metasomatic agents for HMA magma genesis. Since Hf is one of the incompatible elements that may not be readily transported by aqueous fluids, Hf isotopes should provide strong constraints on the origin of such slab‐derived components. Setouchi HMAs and basalts are distinct in their lower 176 Hf/ 177 Hf (ε Hf < +10.8) than MORBs and Izu‐Bonin‐Mariana arc basalts (>+13), suggesting significant contribution of subducted sediments to Setouchi magma genesis. It should be further stressed that Hf isotopes are well correlated with Sr‐Nd isotopes and La/Nb ratios among the Setouchi magmas. Geochemical modeling suggests that such characteristics can be best explained by addition of slab‐derived components with sediment melts rather than aqueous fluids to the HMA source.