Molybdenum Mass Fractions and Stable Isotope Compositions of Sedimentary Carbonate and Silicate Reference Materials

Abstract

A double‐spike method in combination with MC‐ICP‐MS was applied to obtain molybdenum (Mo) mass fractions and stable isotope compositions in a suite of sedimentary silicate (marine, lake, stream, estuarine, organic‐rich sediment, shales, slate, chert) and carbonate reference materials (coral, dolomite, limestones, carbonatites), and a manganese nodule reference material, poorly characterised for stable Mo isotope compositions. The Mo contents vary between 0.076 and 364 μg g−1, with low‐Mo mass fractions (< 0.29 μg g−1) found almost exclusively in carbonates. Intermediate Mo contents (0.73–2.70 μg g−1) are reported for silicate sediments, with the exception of chert JCh‐1 (0.24 μg g−1), organic‐rich shale SGR‐1b (36.6 μg g−1) and manganese nodule NOD‐A‐1 (364 μg g−1). The Mo isotope compositions (reported as δ98Mo relative to NIST SRM 3134) range from −1.77 to 1.03‰, with the intermediate precision varying between ± 0.01 and ± 0.12‰ (2s) for most materials. Low‐temperature carbonates show δ98Mo values ranging from 0.21 to 1.03‰ whereas δ98Mo values of −1.77 and −0.17‰ were obtained for carbonatites CMP‐1 and COQ‐1, respectively. Silicate materials have δ98Mo values varying from −1.56 to 0.73‰. The range of δ98Mo values in reference materials may thus reflect the increasingly important relevance of Mo isotope investigations in the fields of palaeoceanography, weathering, sedimentation and provenance, as well as the magmatic realm.