Barium Isotopic Compositions of Geological Reference Materials

The interest in variations of barium (Ba) stable isotope amount ratios in low and high temperature environments has increased over the past several years. Characterisation of Ba isotope ratios of widely available reference materials is now required to validate analytical procedures and to allow comparison of data obtained by different laboratories. We present new Ba isotope amount ratio data for twelve geological reference materials with silicate (AGV-1, G-2, BHVO-1, QLO-1, BIR-1, JG-1a, JB-1a, JR-1 and JA-1), carbonate (IAEA-CO-9) and sulfate matrices (IAEA-SO-5 and IAEA-SO-6) relative to NIST SRM 3104a. In addition, two artificially fractionated in-house reference materials BaBe12 and BaBe27 (delta Ba-137/134 = -1.161 +/- 0.049 parts per thousand and -0.616 +/- 0.050 parts per thousand, respectively) are used as quality control solutions for the negative delta-range. Accuracy of our data was assessed by interlaboratory comparison between the University of Bern and the United States Geological Survey (USGS). Data were measured by MC-ICP-MS (Bern) and TIMS (USGS) using two different double spikes for mass bias correction (Ba-130-Ba-135 and Ba-132-Ba-136, respectively). MC-ICP-MS measurements were further tested for isobaric and non-spectral matrix effects by a number of common matrix elements. The results are in excellent agreement and suggest data accuracy.