Molybdenum Mass Fractions and Stable Isotope Compositions of Sedimentary Carbonate and Silicate Reference Materials
Natalie Gaspers, Tomáš Magna, Lukáš Ackerman
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 δ 98 Mo relative to NIST SRM 3134) range from −1.77 to 1.03‰, with the intermediate precision varying between ± 0.01 and ± 0.12‰ (2 s ) for most materials. Low‐temperature carbonates show δ 98 Mo values ranging from 0.21 to 1.03‰ whereas δ 98 Mo values of −1.77 and −0.17‰ were obtained for carbonatites CMP‐1 and COQ‐1, respectively. Silicate materials have δ 98 Mo values varying from −1.56 to 0.73‰. The range of δ 98 Mo 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.