DETERMINATION OF LOW CONCENTRATIONS OF U AND TH IN CARBONATE ROCKS USING FI-ICP-MS

The uranium (U) and thorium (Th) concentrations in calcite samples fro m cave deposits were determined using Flow Injection Inductively Coupl ed Plasma Mass Spectrometry (FI-ICP-R;IS) with thallium (T1) as an int ernal standard. The analytical precision in calcite samples containing 200 to 650 mu g/kg U and 10 to 50 mu g/kg Th was 0.5% relative standa rd deviation (RSD) and 1.5% (RSD), respectively, with a limit of detec tion of 70 and 90 ng/kg, respectively. The results were compared with those obtained by Thermal Ionization Mass Spec trometry (TL?IS). Very good correlation factors of 0.998 for U and 0.947 for Th were obtained .