Economically significant mineral deposits, predominantly Pb/Zn, are found in a broad swathe across the centre of Ireland, housed in Carboniferous limestone. All of the deposits are associated with major fault structures, many of which now facilitate groundwater flow. This was observed at Tynagh, Co. Galway and more recently Lisheen in Co. Tipperary and the major deposit at Navan in Co. Meath (Wilkinson&Hitzman,2015). The ability to sample groundwater at these sites presents a rare opportunity to better understand the movement of water in the ground. By analysing the chemistry of the water it is possible to see how genetically distinct structures within the rock supply groundwater with specific chemical signatures that contribute to the broader characterisation of the overall reservoir.