Rare earth element–SiO2 systematics of island arc crustal amphibolite migmatites from the Asago body of the Yakuno Ophiolite, Japan: a field evaluation of some model predictions

Xiaofei Pu, James G. Brophy, Tatsuki Tsujimori

    Research output: Contribution to journalArticle

    2 Citations (Scopus)

    Abstract

    The two most commonly invoked processes for generating silicic magmas in intra-oceanic arc environments are extended fractional crystallization of hydrous island arc basalt magma or dehydration melting of lower crustal amphibolite. Brophy (Contrib Mineral Petrol 156:337–357, 2008) has proposed on theoretical grounds that, for liquids >~65 wt% SiO2, dehydration melting should yield, among other features, a negative correlation between rare earth element (REE) abundances and increasing SiO2, while fractional crystallization should yield a positive correlation. If correct, the REE–SiO2 systematics of natural systems might be used to distinguish between the two processes. The Permian-age Asago body within the Yakuno Ophiolite, Japan, has amphibolite migmatites that contain felsic veins that are believed to have formed from dehydration melting, thus forming an appropriate location for field verification of the proposed REE–SiO2 systematics for such a process. In addition to a negative correlation between liquid SiO2 and REE abundance for liquids in excess of ~65 % SiO2, another important model feature is that, at very high SiO2 contents (75–76 %), all of the REE should have abundances less than that of the host rock. Assuming an initial source amphibolite that is slightly LREE-enriched relative to the host amphibolites, the observed REE abundances in the felsic veins fully support all theoretical predictions.

    Original languageEnglish
    Pages (from-to)1-12
    Number of pages12
    JournalContributions to Mineralogy and Petrology
    Volume168
    Issue number3
    DOIs
    Publication statusPublished - Sep 1 2014

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    Keywords

    • Amphibolite
    • Migmatite
    • Partial melting
    • Rare earth elements
    • Silicic magma

    ASJC Scopus subject areas

    • Geochemistry and Petrology
    • Geophysics

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