Comparative Determination of Mass Fractions of Elements with Variable Chalcophile Affinities in Geological Reference Materials with and without HF Desilicification

Desilicification elevates extraction of Re and platinum-group elements (PGEs) from many geological reference materials (RMs), but the extent to which it affects less chalcophile elements has been investigated rarely. To further evaluate the effect of desilicification, mass fractions of elements with variable chalcophile affinities (In, Cd, Cu, Ag, S, Se, Te, Re and PGEs) in different RMs were obtained by isotope dilution and digestion procedures involving HF-HNO3 in bombs versus HNO3-HCl in Carius tubes. The results show that the extraction efficiencies of HF-desilicification vary in different RMs and for different elements. HF-desilicification led to a significant increase (30-70%) for In and Cd mass fractions in all analysed RMs, but it played a negligible role in other strongly chalcophile elements in many samples (e.g., UB-N and WGB-1). Noticeably, desilicification led to a 10-30% increase in the mass fractions of Cu, Ag, S, Se and Te in BHVO-2 and BIR-1a, but less so in BCR-2. These results could be attributed mainly to the variable chalcophile affinities of elements and their relative budget in sulfides, alloys and silicates. Desilicification should thus be preferred to determine chalcophile elements for most samples, except in cases where they are negligibly hosted in silicates.