Sulphur isotopic investigation of lower carboniferous vein deposits of the British Isles

Similar characteristics and age data suggest that the Pb + Zn vein deposits hosted by Lower Palaeozoic and Vendian strata of the British Isles form a genetically related group, coeval with the Lower Carboniferous carbonatehosted base-metal deposits of Ireland. Sulphur isotopic data demonstrate that there were separate sulphide and sulphate sulphur sources for the vein minerals. ³⁴S values from minerals in individual vein systems are consistent but there is a large variation between deposits, revealing distinctive local sulphur sources. The data suggests that sulphide sulphur (total range of values of ³⁴S_H2S of -6.5 to 18.62) was derived from the underlying strata while the sulphate (baryte) sulphur source (³⁴S_baryte mainly in the range 12 to 24) was groundwater or surface water that mixed with rising hydrothermal fluids in the upper reaches of the veins.