GX-5 Calcite: A New Matrix-Matched Reference Material for In-Situ LA-ICP-MS Carbonate U–Pb Geochronology

Abstract

In-situ laser ablation U–Pb dating for carbonate minerals has emerged as an important technique, providing direct geochronological constraints for hydrocarbon and mineral resources exploration in recent advances in geochronology. Despite the significant potential of this method, a notable deficiency in matrix matching reference materials constrains its accuracy and precision, thereby limiting broader application. In this study, we collected a set of calcite from a massive calcite vein, named GX-5 these are characterized as homogenous low-Mg calcite with high U content (mean value = 6.09 μg g-1) and low common lead composition (f206 mean value = 4.75%) appropriate for in-situ LA-ICP-MS U-Pb geochronology. The in-situ U-Pb dating results of 79 sessions show that the lower intercept age of GX-5 is 78.64±0.1 Ma (2S, MSWD= 5.8, n=168). Meanwhile, the ID-MC-ICP-MS (Isotope Dilution Multi-Collector Inductively Coupled Plasma Mass Spectrometry) U–Pb age determined for GX-5 is 78.88±0.15 Ma (2S, MSWD = 1.07, n=8), with initial 207Pb/206Pb at 0.896±0.039. We propose that GX-5 as a reliable reference material for in-situ U-Pb dating due to its abundant availability, high U content, and stable age characteristics for long term .