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

Abstract

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 Pbc‐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 Pbc‐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 143Nd/144Nd ratios of 0.511587 ± 0.000027 (2s, n = 2) and 0.512321 ± 0.000004 (2s, n = 2), respectively. The 143Nd/144Nd 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.

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“…The titanite was dated as unknowns using a zircon reference material (BB zircon -Santos et al 2017, Lana et al 2017).The matrix related offset between zircon and titanite was calculated at 2% (see Figure5) using the Khan titanite(Kinny et al 1994) as a calibrant to correct the 206 Pb/ 238 U ratios. The same offset was applied to the MKED1 and Khan River titanite.The obtained date for the Khan River and MKED1 titanite sample is identical to the ID-TIMS certified value ofMazoz et al (2022) andSpandler et al (2016), respectively.…”

“…The obtained date for the Khan River and MKED1 titanite sample is identical to the ID‐TIMS certified value of Mazoz et al . (2022) and Spandler et al . (2016), respectively.…”

“…2016 and Khan River titanite of Mazoz et al . 2022). The titanite was dated as unknowns using a zircon reference material (BB zircon ‐ Santos et al .…”

2.13 Ga Lawsonite/Barroisite-Bearing E-Morb Signature Metagabbro Associated with Spinel Metaperidotite from Itaguara (São Francisco Craton, Brazil): Oldest Blueschist-Facies Fragment of Oceanic Moho?

“…All uncertainties on dates/ages are reported as 2s. Four titanite reference material known as Bear Lake, BLR-1, Khan River and Mount Painter have been dated to check measurements, and produced their expected ages of 1064 Ma, 1054 Ma, 542 Ma and 444 Ma respectively [47] .…”