Determination of Zr and Hf in a flux-free fusion of whole rock samples using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) with isotope dilution calibration

Isotope dilution calibration has been applied to the determination of Zr and Hf in whole rocks by laser ablation (LA)-ICP-MS. Enriched isotopes were added during the preparation of flux-free, synthetic whole rock glasses and homogenised through a combination of grinding and fusion. This method avoids problems, such as solution instability and the chemical resistance of minerals such as zircon, inherent in acid digestion sample preparation. The use of isotope dilution removes the need for external calibration using certified reference material glasses such as NIST SRM 612 for which certified Zr and Hf values are not available. The precision of Zr and Hf determinations were found to be < 1% and 3.5% respectively, limited by Poisson counting statistics which contributed to > 50% of the final precision of analysis. Measured values correlate closely with compiled literature values.