Analysis of Re, Au, Pd, Pt and Rh in NIST Glass Certified Reference Materials and Natural Basalt Glasses by Laser Ablation ICP‐MS

Abstract

A new technique for the in situ analysis of Re, Au, Pd, Pt and Rh in natural basalt glass by laser ablation (LA)‐ICP‐MS is described. The method involves external calibration against NIST SRM 612/613 or 614/615 glass certified reference materials, internal standardisation using Ca, and ablation with a 200 μm wide beam spot and a pulsed laser repetition rate of 50 Hz. Under these conditions, sensitivities for Re, Au, Pd, Pt and Rh analyte ions are ˜ 5000 to 100,000 cps/μg g‐1. This is sufficient to make measurements precise to ˜ 10% at the 2‐10 μg g‐1 level, which is well within the range of concentrations expected in many basalts. For LA‐ICP‐MS calibration and a demonstration of the accuracy of the technique, concentrations of Re, Au, Pd, Pt and Rh in the NIST SRM 610/611 (˜ 1 to 50 μg g‐1), 612/613 (˜ 1 to 7 μg g‐1), 614/615 (˜ 0.2 to 2 μg g‐1) and 616/617 (˜ 0.004 to 2 μg g‐1) glasses were determined by solution‐nebulisation (SN)‐ICP‐MS. Using the 612/613 or 614/615 glasses as calibration standards, LA‐ICP‐MS measurements of these elements in the other NIST glasses fell within ˜ 15% of those determined by SN‐ICP‐MS. Replicate LA‐ICP‐MS analyses of the 612/613 and 614/615 glasses indicate that, apart from certain anomalous domains, the glasses are homogeneous for Re, Au, Pd, Pt and Rh to better than 3.5%. Two LA‐ICP‐MS analyses of natural, island‐arc basalt glasses exhibit large fractionations of Re, Au and Pd relative to Pt and Rh, compared to the relative abundances in the primitive mantle.