Characterisation of δ142Ce/140Ce Isotope Ratios in Geological Reference Materials using an SSB plus Sm Doping and MC-ICP-MS Method

We report the delta 142/140Ce values for thirty-three widely available geological reference materials (RMs), including igneous rocks, metamorphic rocks, sediments and soils. The Ce isotope ratios of twenty-two Chinese RMs are reported for the first time. After chemical purification using TODGA resin (50-100 mu m, Eichrom, USA), Ce isotope measurements of these RMs were conducted by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with a combined standard-sample bracketing (SSB) and Sm-doping technique. The data quality of the Ce isotope results was assessed by repeated measurement of pure Ce reference solutions (NIST SRM 3110, JMC304, CDUT-Ce) and well-characterised geological RMs (BHVO-2, BCR-2, Nod-A-1, Nod-P-1, etc.). Our results are in excellent agreement with previously reported values within intermediate measurement precision (+/- 0.04 parts per thousand, 2s). The igneous rock and soil RMs showed limited variations in delta 142/140Ce values, which ranged from -0.036 +/- 0.018 parts per thousand to 0.062 +/- 0.046 parts per thousand and -0.015 +/- 0.015 parts per thousand to 0.029 +/- 0.009 parts per thousand, respectively. The river/marine sediments and Mn nodules displayed variable Ce isotope ratios ranging from -0.005 +/- 0.018 parts per thousand to 0.141 +/- 0.023 parts per thousand, suggesting detectable Ce isotopic fractionation during low-temperature processes.