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Geochemistry of diorites and associated plutonic rocks of SE Jersey, Channel Islands

Published online by Cambridge University Press:  05 July 2018

C. H. Key
C. H. Key*
Affiliation:
Department of Earth Sciences, University of London, Goldsmiths' College, Rachel McMillan Building, Creek Road, Deptford, London, SE8 3BU
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Abstract

The plutonic complex in SE Jersey consists of a late Precambrian gabbro-diorite mass which has been intruded by several granites. The status of the diorites which, like the gabbros, often possess a layered structure, is not clear. New geochemical data, including rare earth and trace element analyses, suggest that acid-basic magma mixing was not responsible for the variety of intermediate rocks. Amphibole-controlled fractional crystallization of hydrous basic magma is also unlikely in view of the REE and HFS (high field strength) element distribution. The model which best fits all the available field, petrographic and geochemical evidence is one in which the chemical variation was initially produced by fractional crystallization of anhydrous basic magma and subsequently overprinted by granitic metasomatism. This superimposed calc-alkaline characteristics on the complex and produced hybrid diorites which, because they were above their solidus temperature, recrystallized with textures indicative of a magmatic origin.

Keywords

geochemistrydioriteChannel Islands
Type
Geochemistry
Information
Mineralogical Magazine , Volume 51 , Issue 360 , June 1987 , pp. 217 - 229
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1987

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