A gravity and magnetic interpretation of the structure of the Irish Midlands and its relation to ore genesis.

In the area of the Lower Carboniferous limestones of central Ireland, magnetic data suggest that the Precambrian crystalline basement is at a depth of 3-4 km, and is overlain by Ordovician volcanic rocks. Residual gravity values indicate the presence of a series of linear volcanic blocks and sedimentary troughs trending NE-SW; the major mineralized zones in the area all occur close to the margins of these troughs. The genesis of the orebodies is probably associated with de-watering of the shale-filled troughs, the subsequent concentration of metal-bearing fluids along the margins and their deposition in relatively unladen carbonate host rocks on the up-standing blocks.-R.A.H.