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The Skye Main Lava Series: liquid density and the absence of basaltic hawaiites

Published online by Cambridge University Press:  01 May 2009

A. C. Cattell
A. C. Cattell
Affiliation:
Department of Geology, University of Exeter, Exeter EX4 4QE, U.K.
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Abstract

Basaltic hawaiite lavas are virtually absent in the Eocene Skye Main Lava Series, in contrast to relatively abundant basalts and hawaiites. Fractional crystallization from basalt to basaltic hawaiite involves extraction of a large proportion of plagioclase, and liquid densities thereby increase. From basaltic hawaiite to hawaiite titanomagnetite is a significant fractionating phase, and liquid densities decline. The coincidence between a gap in erupted compositions and a density maximum implies that liquid density exerted a strong control on ‘eruptibility’ of magmas; basaltic hawaiites were too dense to be erupted. Density maxima occur in basalt suites if plagioclase fractionates before Fe–Ti oxides, and may explain compositional gaps in erupted magmas. Compositional gaps are not the inevitable result of density maxima; the density of the rock column above, and the fluid dynamics within, the magma chamber where differentiation occurs are also critical factors.

Type
Articles
Information
Geological Magazine , Volume 126 , Issue 6 , November 1989 , pp. 681 - 684
Copyright
Copyright © Cambridge University Press 1989

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