KV01 zircon—A potential New Archean reference material for microbeam U-Pb age and Hf-O isotope determinations

Abstract

To meet the rapid development of zircon U-Pb geochronology and Hf-O isotope geochemistry, it is imperative to develop well-characterized zircon reference materials for microbeam analysis. Here, zircon KV01 separated from the Kaap Valley pluton, South Africa is introduced as a potential Archean reference material for microbeam U-Pb age and Hf-O isotope determination. SIMS and LA-ICP-MS U-Pb isotopic measurements gave grand mean 207Pb/206Pb ages of 3233±16 Ma (2s, n=90) and 3230±26 Ma (2s, n=52), which are consistent with reported CA-ID-TIMS results. Slight heterogeneity of oxygen isotopes is revealed by SIMS analyses that yielded a relatively large δ18O range of 4.61–6.51‰. Among them, the zircon grains with clear oscillatory zones give a grand mean δ18O value of 6.17±0.33‰ (2s), which is suggested to record the primary O isotopic compositions. The homogeneity in the Hf isotopic compositions of KV01 zircon was checked by the laser ablation and solution MC-ICP-MS methods. They yielded consistent results with a recommended 176Hf/177Hf ratio of 0.280810±0.000013 (2s). The results reported here demonstrate that KV01 zircon could be a reliable reference material for microbeam 207Pb/206Pb age and Hf isotope determinations of ancient zircons, and be suitable as a quality monitor for SIMS oxygen isotopic analysis.