Contact Metamorphism and Fluid Movement Around the Easky Adamellite, Ox Mountains, Ireland

Bruce W. D. Yardley and C. Barry Long
School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ
Geological Survey of Ireland, 14 Hume Street, Dublin 2, Ireland

Abstract: Contact metamorphism in the aureole of the Easky adamellite produced andalusite at the expense of regional staurolite, kyanite, and garnet. In the inner aureole sillimanite and K-feldspar also grew. Cordierite is only rarely present. Conditions of metamorphism in the inner aureole have been deduced from five independent criteria as 595 ± 30 °C and 2.5 ± 0.5kb. The nearby Lough Talt adamellite was emplaced at slightly higher pressures. Some aureole rocks have undergone oxidation with conversion of regional garnet to magnetite and andalusite. The reacting assemblage buffered O2 near 10−17 bars. It is inferred that oxidation was caused by movement of H2O from the country rocks into the intrusion.

Mineralogical Magazine; June 1981 v. 44; no. 334; p. 125-131; DOI: 10.1180/minmag.1981.044.334.01
© 1981, The Mineralogical Society
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