Abstract

The mineralization which resulted in the base metal deposits hosted in carbonates of Lower Carboniferous (Dinantian) age in Ireland is in most deposits younger than their mainly Tournaisian-aged host rocks. The stratigraphical age of mineralization at Navan has been shown to be mostly pre-Arundian in age. In the Lisheen deposit in the Rathdowney Trend, development of massive sulphide mineralization post-dated regional dolomitization of late Tournaisian Waulsortian Limestone. Estimates from fluid inclusion and oxygen isotope data of the temperatures at which dolomitization took place suggests that the depth of burial at the time of dolomitization must have been greater than that achieved by early Arundian time, indicating that mineralization at Lisheen was later, and perhaps substantially later, than at Navan. Mineralization coincided with, or post-dated, maximum downthrow on extensional faults atLisheen; maximum downthrow, therefore, was not attained until after the beginning of Arundian time. If minealization of the Irish deposits, rather than being restricted to a narrow interval of time (Lower Viséan-early Arundian), as has been suggested in recent reviews, continued into the younger parts of the Viséan, later Viséan rocks in Ireland should be considered to be potential targets for exploration.