Khan River and Bear Lake: Two Natural Titanite Reference Materials for High‐Spatial Resolution U‐Pb Microanalysis

The Khan River (Namibia) and Bear Lake (Canada) titanites are investigated as potential reference materials (RM) for LA-ICP-MS applications. The Bear Lake titanite is texturally and compositionally homogeneous. The Khan River titanite is texturally heterogeneous and characterised by variable trace element compositions and total rare earth element contents. However, both titanites have consistent U-Pb and Nd-isotope ratios. U-Pb isotope dilution-thermal ionisation mass spectrometry analyses yielded Pb-c-uncorrected intercept ages of 516.3 +/- 1.3 Ma (2s, n = 5, MSWD = 2.4) and 1067.81 +/- 0.74 Ma (2s, n = 4, MSWD = 0.35) for Khan River and Bear Lake titanites, respectively. Multiple U-Pb LA-SF/MC-ICP-MS analyses gave consistent Pb-c-uncorrected intercept ages for both, Khan River (517 +/- 1/5 Ma, 2s, n = 262, MSWD = 1.5) and Bear Lake (1070 +/- 1/11 Ma, 2s, n = 325, MSWD = 0.88). U-Pb SHRIMP analyses on the same material returned identical (within uncertainty) ages. Khan River and Bear Lake gave internally consistent solution MC-ICP-MS Nd-143/Nd-144 ratios of 0.511587 +/- 0.000027 (2s, n = 2) and 0.512321 +/- 0.000004 (2s, n = 2), respectively. The Nd-143/Nd-144 ratios via solution-MC-ICP-MS and LA-ICP-MS all agree within uncertainty and suggest that both titanites can be used as RMs for Nd-isotope analyses.