Stable W Isotope Measurements of Geological Reference Materials and Tungsten Ore Minerals by Double Spike MC‐ICP‐MS

Abstract

This study presents high‐precision W isotopic measurement results using the 180W‐183W double spike technique with MC‐ICP‐MS. The effects of isobaric and polyatomic interferences on W isotopic measurements were evaluated. The δ186/184W values were not significantly affected when the solution had Hf/W ≤ 3 × 10‐4, Ta/W ≤ 1, Os/W ≤ 0.06, Ce/W ≤ 0.0075, Nd/W ≤ 3.5 and Sm/W ≤ 5. The intermediate measurement precisions of both standard solutions (NIST SRM 3163 and Alfa Aesar W) and geological reference materials (NOD‐A‐1) were better than ±0.024‰ (2s). We also obtained a precision of 0.026‰ for a minimum sample loading mass of 5 ng, allowing the analysis of samples with low W contents. Replicated measurements of geological reference materials (AGV‐2, BCR‐2, BHVO‐2, GSP‐2, RGM‐1, SDC‐1, NOD‐A‐1 and NOD‐P‐1) yielded δ186/184W values ranging from 0.017‰ to 0.144‰. The δ186/184W values of two major tungsten ore minerals (scheelite and wolframite) were reported and compared herein. Scheelites had systematically slightly heavier W isotopic compositions than wolframites, which may reflect differences in the crystal structure. The resolvable variations of stable/mass‐dependent W isotopic compositions in rocks and ore minerals make W isotopes a novel tool for studying hydrothermal mineralisation processes and the W cycle of geological reservoirs.