Mg Isotope Interlaboratory Comparison of Reference Materials from Earth-Surface Low-Temperature Environments

To enable quality control of measurement procedures for determinations of Mg isotope amount ratios, expressed as Mg-26 and Mg-25 values, in Earth-surface studies, the Mg-26 and Mg-25 values of eight reference materials (RMs) were determined by interlaboratory comparison between five laboratories and considering published data, if available. These matrix RMs, including river water SLRS-5, spring water NIST SRM 1640a, Dead Sea brine DSW-1, dolomites JDo-1 and BCS-CRM 512, limestone BCS-CRM 513, soil NIST SRM 2709a and vegetation NIST SRM 1515, are representative of a wide range of Earth-surface materials from low-temperature environments. The interlaboratory variability, 2s (twice the standard deviation), of all eight RMs ranges from 0.05 to 0.17 parts per thousand in Mg-26. Thus, it is suggested that all these materials are suitable for validation of Mg-26 and Mg-25 determinations in Earth-surface geochemical studies.