REE enrichment in groundwaters of the polysulphide ore deposit Freiberg

The rare earth elements (REE) are considered to be relatively immobile during weathering and alteration of rocks (e.g., MCLENNAN 1989), though more recent studies have shown, that at least the light REE (LREE) are not that immobile (e.g., PRICE et al. 1991; POLAT et al. 2003). The assumed immobility was in part based on the low concentration of REE in river and ocean waters (typically in the range x – xx µg/l; e.g. ELDER-FIELD et al. 1990). Likewise, the high ionic po-tential suggests that the REE are expected to be rather immobile in aqueous environments, as they should tend to form hydroxides. The advent of analytical procedures with higher sensitivity, in particular ICP-MS techniques, have stimulated renewed interest in the aqueous geochemistry of the REE (e.g., ELDERFIELD et al. 1990). MÖLLER (2000) and WORRAL & PERSON (2001) for example, used REE patterns of groundwaters as fingerprints for the identifica-tion of the host rocks of groundwaters. Preliminary work by BAAKE et al. (1989) has shown, that acid mine waters and sinter deposits in the polysulfide ore deposit Freiberg are in part highly enriched in REE. This study extends this work in order to adress the following questions: 1. what is the source of the REE concentrated in acid mine waters, the host rocks of the de-posit (i.e. the Freiberg Gray Gneiss) or gan-gue (i.e. calcite, fluorite)? 2. what controls the REE patterns in acid mine waters, the composition of the REE source or interaction of the waters and deposits (sin-ters)? The present contribution is largely a status report on ongoing research and is mainly focussed on the chemistry of the mine waters.