RKV01 Rutile – A New Potential Archaean Reference Material for Microbeam U‐Pb Dating

Abstract

Rutile stands as a classical mineral within U‐Pb geochronology, offering insights into both magmatic and metamorphic events, and contributing to the understanding of provenance of detrital sedimentary rocks. Addressing the paucity of high‐quality Archaean rutile reference materials suitable for microbeam U‐Pb dating, we present a natural rutile (RKV01) sourced from the Kaap Valley pluton, South Africa, positing it as a potential Archaean reference material. Major element determination was executed via electron probe microanalysis, while trace element determination was conducted using laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The determination of U‐Pb ages involved the application of isotope dilution‐thermal ionisation mass spectrometry (ID‐TIMS), secondary ion mass spectrometry (SIMS) and LA‐ICP‐MS. The ID‐TIMS mean 207Pb/206Pb age is 3225.61 ± 0.64 Ma (2s, MSWD = 0.83), interpreted as the best estimate for the crystallisation age. The relatively high U mass fraction (~ 83 μg g‐1), extremely low Th mass fraction (~ 0.003 μg g‐1), negligible common Pb and isotopically homogeneous compositions collectively facilitated precise 207Pb/206Pb age determination via microbeam methods. Both LA‐ICP‐MS and SIMS 207Pb/206Pb ages are characterised by reproducibility and were consistent with the ID‐TIMS age within 2s analytical uncertainty. The results underscore the potential of RKV01 rutile as an Archaean reference material for microbeam U‐Pb dating.