Alkali Feldspars from Part of the Galway Granite, Ireland

J. R. Wilson and J. S. Coats
Geologisk Institut, Aarhus Universitet, Ole Worms Alle, 8000 Århus C, Denmark
Institute of Geological Sciences, 64-78 Grays Inn Road, London W.C. I, Great Britain

Summary: The structural states of alkali feldspars from the eastern end of the Galway Granite show transitions from orthoclase to microcline as a result of late deformation. Analyses of twenty samples for SiO2, Al2O3, TiO2, Fe2O3, CaO, Na2O, K2O, S, Cu, Zn, Ga, Rb, Sr, Ba, and Pb agree with previously determined orders of entry of elements into the ‘alkali site’. A relationship between this order of entry and the melting points of feldspar end-members is discussed.

Mineralogical Magazine; September 1972 v. 38; no. 299; p. 801-810; DOI: 10.1180/minmag.1972.038.299.04
© 1972, The Mineralogical Society
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