The Geochemistry of Lower Tertiary Basic Dykes in the Eastern Red Hills District, Isle of Skye, and Their Significance for the Proposed Magmatic Evolution of the Skye Centre

B. R. Bell
Department of Geology*, Imperial College of Science and Technology, London SW7 2BP
*Present address: Department of Apptied Geology, University of Strathclyde, Glasgow G1 1XJ, Scotland.

Abstract: Major- and trace-element data are presented for basic dykes intruding the Eastern Red Hills district of the Tertiary igneous centre of Skye. In addition to a group of transitional basic intrusions, members of two other distinctive suites have been identified: (1) a series of basic alkaline intrusions (akin to the ‘Beinn Dearg Type’ of Harker, 1904), with characteristic high alkali contents, distinctive values of K2O/(K2O + Na2O) and rare-earth-element (REE) patterns similar to those of many of the Tertiary lavas of north Skye, and, (2) tholeiitic dykes, with low concentrations ofK2O, Ti/Zr values of c., 100, and flat REE patterns similar to those of the so-called Fairy Bridge magma type (Mattey et al., 1977). From these data and a consideration of the time relationships of the various components of the Skye Centre, agreement is found with Thompson et al.'s (1972, 1980) model of a mantle thermal anomaly which generates the magmatic sequence: transitional basic magmas, giving way to olivine-bearing tholeiitic magmas (at the culmination of the anomaly), and, finally, late-stage basic alkaline magmas at the end of the activity.

Mineralogical Magazine; September 1984 v. 48; no. 348; p. 365-372; DOI: 10.1180/minmag.1984.048.348.06
© 1984, The Mineralogical Society
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