Rare earth element-Si[O.sub.2] systematics of island arc crustal amphibolite migmatites from the Asago body of the Yakuno Ophiolite, Japan: a field evaluation of some model predictions

Citation metadata

Date: Sept. 2014
Publisher: Springer
Document Type: Article
Length: 4,324 words
Lexile Measure: 1440L

Document controls

Main content

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% Si[O.sub.2], dehydration melting should yield, among other features, a negative correlation between rare earth element (REE) abundances and increasing Si[O.sub.2], while fractional crystallization should yield a positive correlation. If correct, the REE-Si[O.sub.2] 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-Si[O.sub.2] systematics for such a process. In addition to a negative correlation between liquid Si[O.sub.2] and REE abundance for liquids in excess of ~65% Si[O.sub.2], another important model feature is that, at very high Si[O.sub.2] 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. Keywords Amphibolite * Migmatite * Rare earth elements * Partial melting * Silicic magma

Source Citation

Source Citation   

Gale Document Number: GALE|A389176417