Geochemistry of rare earth elements in groundwater from deep seated limestone aquifer in Renlou Coal

Rare earth element (REE) concentrations were measured by ICP-MS for groundwater collected from deep seated Taiyuan Fm limestone aquifer (from -400 to -530 m) in Renlou Coal Mine,northern Anhui Province,China.It can be concluded that the groundwater is warm (34.0-37.2 ℃) Cl-Ca,Na type water with circum-neutral pH (7.35-8.28) and high total dissolved solids (TDS,1 746-2 849 mg/L).The groundwater exhibits heavy REEs ertrichment relative to light REEs compared with Post Archean Average Shale (PAAS),as well as their aquifer rocks (limestone).The enrichment of REEs is considered to be controlled by terrigeneous materials (e.g.zircon) in aquifer rocks,whereas the fractionation of REEs is controlled by marine derived materials (e.g.calcite),to a less extent,terrigeneous materials and inorganic complexation.The Ce anomalies normalized to PAAS and aquifer rocks are weak,which probably reflects the signature of the aquifer rock rather than redox conditions or pH.The similarities of REE patterns between groundwater and aquifer rocks imply that aquifer rocks play important roles in controlling the REE characteristics of groundwater,and then provide a probability for discrimination of groundwater sources by using REEs.