Professor Ian Sanders of TCD will give a talk on Metamorphic Rocks in the North-eastern Ox Mountains Inlier.   

Abstract:
Unusual metamorphic rocks, unique in these islands and rare in the world, are preserved in the northeastern limb of the Ox Mountains inlier, which is a narrow strip of old rock trending diagonally across the country to the SE of Sligo town and bordered on both sides by younger Carboniferous limestone. The rocks are derived mainly from basaltic and sedimentary parents, and they reached temperatures approaching 900°C and depths of between 30 and 40 km, probably about 470 million years ago during the early Ordovician period.    

In the talk I will describe a suite of these rocks which I collected from an area south of Lough Gill. I will discuss the kinds of rock they were originally, before becoming metamorphosed. I will ask how the enormous depths and temperatures they are believed to have experienced were estimated and will show evidence for how the pressure and temperature conditions changed through time. I will ask how the age of the metamorphism has been inferred, and I will conclude by speculating briefly on how the story of these rocks relates to our general understanding of how plate-tectonic processes affected rocks in the west and northwest of Ireland during the early Ordovician.