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The disequilibrium partial melting and assimilation of Caledonian granite by Tertiary basalt at Barnesmore, Co. Donegal

Published online by Cambridge University Press:  01 May 2009

D. E. Kitchen
D. E. Kitchen
Affiliation:
Department of Environmental Studies, University of Ulster, Jordanstown, Co. Antrim, BT37 0QB, Northern Ireland, U.K.
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Abstract

A regional Tertiary basaltic dyke swarm intensifies within a Caledonian granite at Barnesmore, Co. Donegal. Rapid heating along the contact of one (possible feeder) dyke resulted in disequilibrium partial melting of granite wall-rock and the generation of a range in melt composition by the in situ melting of feldspar. The compositional variability of the melt is preserved in a glass containing feldspar spherulites and other quench phases which suggest rapid cooling. During partial melting the trace elements, Rb, Sr, and Ba were mobile and have been concentrated in glassy melted granite close to the contact of one dyke. The textures, mineralogy and geochemistry of dolerite in two dykes indicate localized bulk contamination and mixing with melted granite. This had a particularly marked effect on the crystallization of pyroxene and resulted in a wide range in mineral composition reflecting the degree of contamination. The intensification of a regional dyke swarm in well-jointed granite might control the siting of some major intrusive centres. Granite melted and mixed with basaltic magma may contribute to the evolution of granites in such centres.

Type
Articles
Information
Geological Magazine , Volume 126 , Issue 4 , July 1989 , pp. 397 - 405
Copyright
Copyright © Cambridge University Press 1989

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