Abstract

The Irish Dalradian was locally heated to garnet zone temperatures prior to the development of major isoclinal fold structures, possibly at moderately high pressures. The peak of Barrovian metamorphism was reached after the major structures had formed. In Connemara, metamorphism may have been initially of Buchan type in the S, where synorogenic intrusions occur. Connemara suffered subsequent development of major northward facing nappe structures and the high grade rocks were thrust over low grade metasediments in the S, possibly indicating continent-continent collision. This deformation was accompanied by uplift, and low pressure assemblages were superimposed on earlier Barrovian metamorphism in the N. Thermal aureoles around post-tectonic granites show that most Irish Dalradian rocks underwent uplift and erosion after folding, and before granite emplacment. The highest metamorphic grades are now exposed in Connemara, Tyrone and in a region from Belmullet to Castlederg that is centred around windows of probable basement.

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