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Dynamic melting in plume heads: the formation of Gorgona komatiites and basalts

Arndt, N. T., Kerr, Andrew Craig and Tarney, J. 1997. Dynamic melting in plume heads: the formation of Gorgona komatiites and basalts. Earth and Planetary Science Letters 146 (1-2) , pp. 289-301.

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Abstract

The small Pacific island of Gorgona, off the coast of Colombia, is well known for its spectacular spinifex-textured komatiites. These high-Mg liquids, which have been linked to a late Cretaceous deep mantle plume, are part of a volcanic series with a wide range of trace-element compositions, from moderately enriched basalts (La/Sm, - 1.5) to extremely depleted ultramafic tuffs and picrites (La/Sm, - 0.2). Neither fractional crystallization, nor partial melting of a homogeneous mantle source, can account for this large variation: the source must have been chemically heterogeneous. Low j4’Nd/ ‘@Nd in the more enriched basalts indicates some initial source heterogeneity but most of the variation in magma compositions is believed to result from dynamic melting during the ascent of a plume. Modelling of major- and trace-element compositions suggests that ultramafic magmas formed at u 60-100 km depth, and that the melt extraction that gave rise to their depleted sources started at still greater depths. The ultra-depleted lavas represent magmas derived directly from the hottest, most depleted parts of the plume; the more abundant moderately depleted basalts are interpreted as the products of pooling of liquids from throughout the melting region.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: komatiite ; Gorgona Island Colombia ; geochemistry ; mantle plumes ; melting.
Publisher: Elsevier
ISSN: 1385-013X
Last Modified: 04 Jun 2017 02:08
URI: http://orca.cf.ac.uk/id/eprint/9575

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