Correlated petrographic and isotopic studies (S, Pb) of carbonate-hosted Zn-Pb mineralization: the formation of the high-grade Island Pod, Lisheen

Irish Zn-Pb deposits are a type of carbonate-hosted mineralization, typically found adjacent to normal faults. Ore deposition occurred due to the replacement of Lower Carboniferous limestones, triggered primarily by fluid mixing. The Lisheen deposit (23 Mt at 13.3% Zn & 2.3% Pb) in the southern Irish orefield consists of several stratabound orebodies, which are strongly controlled by a left-stepping, ramp-relay fault array. The Island Pod (0.4 Mt at 20% Zn & 1.6% Pb) is a small high-grade orebody, found in the northern part of the Lisheen mine (Fig. 1). We present the first detailed petrographic and paragenetically constrained S-Pb isotopic study and mineral chemical analysis of the Island Pod mineralization. Homogenous Pb isotopic signatures in galena have been observed throughout the Island Pod, regardless of paragenetic stage. Sulfur isotope ratios vary but suggest a dominantly bacteriogenic source for S. Sulfide minerals have low trace element concentrations, below electron microprobe detection limits for most elements.