The zircon ‘matrix effect’: Evidence for an ablation rate control on the accuracy of U–Pb age determinations by LA-ICP-MS

摘要: Many studies now acknowledge the occurrence of systematic discrepancies between U–Pb ages determined in zircons situ by LA-ICP-MS and benchmark analytical method ID-TIMS. In this study, we present detailed investigations into ablation characteristics that suggest an underlying mechanism responsible for these age biases relative to Confocal laser scanning microscopy pits reveals there are small but significant differences amount material removed different zircons. Based on numerous pit depth 206Pb/238U ratio measurements a suite natural zircon reference materials samples, demonstrate bias is strongly correlated with offset rates primary sample We offer further insights concerning effects thermal annealing behaviour that, although change annealed zircons, variations not eliminated. Finally, show slight focus also influence may degrade accuracy determinations.