Chemical Variation of Clinopyroxene Phenocrysts from the Trachybasaltic Lavas of Mount Etna, Sicily

A. M. Duncan and R. M. F. Preston
Geology Section, Department of Science, Luton College of Higher Education, Luton LU1 3JU
Department of Geology, University College London, Gower Street, London WC1E 6BT

Summary: The chemical variation of clinopyroxene phenocrysts from the trachybasaltic lavas of Etna volcano is described. The phenocrysts show a limited, but distinct trend in chemical variation from calcic-augite in the hawaiites to augite in the benmoreites. The trend of this variation is unusual, being one of Mg-enrichment with differentiation of the magma. Ca shows a steady decrease in the clinopyroxenes from the hawaiites to the benmoreites. Na, however, shows little chemical variation in the pyroxenes. The trace element chemistry is briefly examined. The clinopyroxenes show well-developed oscillatory and sector zoning. The basal {111} sectors are enriched in Si and Mg and depleted in Ti, Al, and Fe relative to the {100}, {110}, and {010} prism sectors.

Mineralogical Magazine; June 1980 v. 43; no. 330; p. 765-770; DOI: 10.1180/minmag.1980.043.330.10
© 1980, The Mineralogical Society
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