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 ℃） C1-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 enrichment 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.
Deep coal mines in northern Anhui province, China, provide opportunities for tracing the distribution and fractionation of rare earth elements CREEs） in deep seated environments. Major ions, as well as REE concentrations were measured in groundwater from a sandstone aquifer located between -400 and -280 m. Our results indicate that this groundwater consists of CI.HCOH-Na or CI.CO3-Na water types with warm temperature （30.1-31.4~C）, circumneutral pH （7.27-8.61） and high levels of total dissolved solids （TDS ~ 1306--2165 mg/L）. Concentrations of REEs in groundwater are high as expressed by their Nd con- centrations （0.0086-0.018μg/L）. Except for weak heavy REEs （HREE） enrichment relative to light REEs （LREE）, the similarity of REE distribution patterns between groundwater and aquifer rock indicate that enrichment of REEs is considered to be controlled by aquifer rock, as well as by their minerals, whereas the fractionation of REEs is controlled by HREE enriched minerals and, to a lesser extent, by inorganic REE complexes. Ce anomalies normalized to Post Archean Average Shale （PAAS） and aquifer rock are weak, which probably reflect the contribution of reduced conditions in combination with pH, rather than a sig- nature of aouifer rock.
