Trace element evaluation of a suite of rocks from Reunion Island, Indian Ocean

Geochimica et Cosmochimica Acta
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Abstract

Reunion Island consists of an olivine-basalt shield capped by a series of flows and intrusives ranging from hawaiite through trachyte. Eleven rocks representing the total compositional sequence have been analyzed for U, Th and REE. Eight of the rocks (group 1) have positive-slope, parallel, chondrite-normalized REE fractionation patterns. Using a computer model, the major element compositions of group 1 whole rocks and observed phenocrysts were used to predict the crystallization histories of increasingly residual liquids, and allowed semi-quantitative verification of origin by fractional crystallization of the olivine-basalt parent magma. Results were combined with mineral-liquid distribution coefficient data to predict trace element abundances, and existing data on Cr, Ni, Sr and Ba were also successfully incorporated in the model. The remaining three rocks (group 2) have nonuniform positive-slope REE fractionation patterns not parallel to group 1 patterns. Rare earth fractionation in a syenite is explained by partial melting of a source rich in clinopyroxene and/or hornblende. The other two rocks of group 2 are explained as hybrids resulting from mixing of syenite and magmas of group 1. 

Publication type Article
Publication Subtype Journal Article
Title Trace element evaluation of a suite of rocks from Reunion Island, Indian Ocean
Series title Geochimica et Cosmochimica Acta
DOI 10.1016/0016-7037(75)90012-5
Volume 39
Issue 5
Year Published 1975
Language English
Publisher Elsevier
Description 22 p.
First page 713
Last page 734
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