Geological controls on mineralization and dolomitization of the Lisheen Zn-Pb-Ag deposit, Co. Tipperary, Ireland

The Lisheen deposit is a stratabound Zn-Pb-Ag deposit hosted in dolomitized Waulsortian limestone of Courceyan age. The deposit was discovered in April 1990 and the current resource is estimated to be 22 million tonnes at 11.5% Zn, 2% Pb and 16% Fe, with 26 g/t Ag. Lisheen is located along the Rathdowney Trend, a NE-SW trending, structurally controlled belt of carbonate rocks. Sulphides are present in the hanging wall of two major E to NE-trending normal faults, the Killoran and Derryville faults. These structures are large, northerly-dipping normal faults with displacements of approximately 200 m. The Killoran and Derryville structures form short fault segments of a major relay fault system that extends along the Rathdowney Trend. Faults are observed to have influenced sedimentation, and exercized a major control on the distribution of mineralization, hydrothermal alteration and dolomitization. Several phases of dolomitization, which affect Chadian rocks and temporally overlapped mineralization, help to constrain the timing of this mineralization to no earlier than the late Chadian.