Systematic Characterisation of Natural Titanite Reference Materials (Ontario, T3 and Pakistan) for High Spatial‐Resolution U‐Pb Microanalysis

Three previously introduced titanites, Ontario, T3 and Pakistan, were evaluated as potential reference materials (RMs) for high spatial‐resolution U‐Pb microanalysis, offering valuable additions to the currently limited suite of titanite RMs. Comprehensive characterisation through microanalytical techniques, including scanning electron microscope, electron probe micro‐analysis, secondary ion mass spectrometry (SIMS) and laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS), reveal that the Proterozoic‐age Ontario titanite is inclusion‐free and homogeneous within analytical uncertainty in terms of major and trace elements, U‐Pb isotopes and U‐Pb ages. The Miocene‐age Pakistan titanite, though relatively low in U and Pb contents, also shows homogeneity in U‐Pb isotopes and ages at the scale of analytical precision. Isotope dilution thermal ionisation mass spectrometry (ID‐TIMS) results are reported for the first time for both Ontario and Pakistan titanites. Accordingly, analyses of the Ontario titanite fragments range from concordant to variably discordant but yield a robust weighted mean ²⁰⁷ Pb/ ²⁰⁶ Pb date of 1048.5 ± 3.3 Ma (2 s “internal” uncertainty, n  = 9). Cross‐calibration with other titanite RMs by LA‐ICP‐MS demonstrates that Ontario is suitable as a primary RM for determining U‐Pb ages of titanite ranging in age from Precambrian to Neogene. ID‐TIMS analyses of the Pakistan titanite yield overlapping data with a weighted mean ²⁰⁶ Pb/ ²³⁸ U date of 20.759 ± 0.055 Ma (2 s “internal” uncertainty, n = 10). Considering its relatively young age, Pakistan titanite is recommended as a secondary RM for quality control of young titanites dating by LA‐ICP‐MS and SIMS. In contrast, the T3 titanite exhibits significant intra‐ and inter‐grain heterogeneity. The brighter zone in BSE images (T3‐LG) has relatively high and homogeneous rare earth elements contents and yields a lower intercept age of 1099 ± 3 Ma (2 s , n = 78, MSWD = 1.3) by LA‐ICP‐MS. In contrast, darker domains display heterogeneous trace element and ages, rendering them unsuitable as RMs for microbeam U‐Pb dating.