Clinopyroxenes and Biotites from the Centre III Igneous Complex, Ardnamurchan, Argyllshire

J. N. Walsh
Department of Geology, King's College, Strand, London, WC2R 2LS

Summary: Major- and trace-element analyses of the clinopyroxenes and biotites from the ring-intrusions of Centre III in the Tertiary igneous complex of Ardnamurchan are presented. It is shown that there are systematic differences in mineral chemistry between the eucrites, the gabbros, and the dolerites, and in particular the clinopyroxenes show an iron enrichment trend that is similar to that found in fractionated tholeiitic intrusions. The minerals from the intcrmediate rocks, the tonalite and quartz monzonite in the centre of the complex, do not show the further iron enrichment expected if these rocks had formed by continued fractionation of basic magma. On the basis of the chemistry of the clinopyroxenes and biotites, the intermediate rocks are interpreted as hybrids formed by the remelting and assimilation of country rocks into basic magma.

Mineralogical Magazine; December 1975 v. 40; no. 312; p. 335-345; DOI: 10.1180/minmag.1975.040.312.02
© 1975, The Mineralogical Society
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