Molybdenum Mass Fractions and Isotopic Compositions of International Geological Reference Materials

The double-spike method with multi-collector inductively coupled plasma-mass spectrometry was used to measure the Mo mass fractions and isotopic compositions of a set of geological reference materials including the mineral molybdenite, seawater, coral, as well as igneous and sedimentary rocks. The long-term reproducibility of the Mo isotopic measurements, based on two-year analyses of NIST SRM 3134 reference solutions and seawater samples, was <= 0.07 parts per thousand (two standard deviations, 2s, n = 167) for delta Mo-98/95. Accuracy was evaluated by analyses of Atlantic seawater, which yielded a mean delta Mo-98/95 of 2.03 +/- 0.06 parts per thousand (2s, n = 30, relative to NIST SRM 3134 = 0 parts per thousand) and mass fraction of 0.0104 +/- 0.0006 mu g g(-1) (2s, n = 30), which is indistinguishable from seawater samples taken world-wide and measured in other laboratories. The comprehensive data set presented in this study serves as a reference for quality assurance and interlaboratory comparison of high-precision Mo mass fractions and isotopic compositions.