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