Application of stable environmental isotopes in mine hydrogeology taking Polish coal basins as an example

Preliminary results of the stable isotope investigations carried out in Polish coal basins are presented. In the case of the Lublin Coal Basin, the extreme values of δ18O lie between -10.05 and -4.95 per mille, and of δD from -71. 99 to -41.40 per mille. The tested waters may be divided into two groups regarding the relative isotope content. The first group includes waters with overall mineralization lying between 0.4 and 2.5 g/litre. All the waters from the overburden may be placed in this group, and also most of those from the productive Carboniferous. The low content of heavy isotopes allows this group to be classified as infiltration waters. Hence it must be expected that water inflows to the mines will come from both static and dynamic sources. Waters from the Carboniferous with mineralization higher than 10 g/litre are grouped separately. On the precipitation line these points are shifted to the SMOW values. These waters represent a mixture of relict and infiltration waters. If mining is taken to a depth greater than 1000 m, only a minimal proportion of waters from the dynamic sources in mine inflows need be expected. In the case of the Upper Silesian Coal Basin, extreme values of δ18O vary from -11.57 to +0.34 per mille, and δD from -72.9 to -1.2 per mille. From analysis of the diagram showing the relation between δ18O and δD contents the deep infiltration of contemporary atmospheric waters in the productive Carboniferous of the northern, hydrogeologically non-isolated sector of the Coal Basin is evident. In the southern isolated sector of the basin no recent freshening of the waters under Tertiary overburden is observed. In the formations of varied geological age occurring below 600 m, relict waters appear. It may therefore be predicted that inflow to new mines scheduled for construction will be from static resources only. (author)