Preprints
https://doi.org/10.5194/gchron-2024-7
https://doi.org/10.5194/gchron-2024-7
06 Mar 2024
 | 06 Mar 2024
Status: this preprint is currently under review for the journal GChron.

Technical note: RA138 Calcite U-Pb LA-ICP-MS primary reference material

Marcel Guillong, Elias Samankassou, Inigo A. Müller, Dawid Szymanowski, Nathan Looser, Lorenzo Tavazzani, Óscar Merino-Tomé, Juan R. Bahamonde, Yannick Buret, and Maria Ovtcharova

Abstract. A promising primary reference material for U-Pb LA-ICP-MS carbonate dating is analysed and reported here. The new RM is a botryoidal cement (C1) from sample RA138. The sample was collected in outcrop strata of mid-Carboniferous (Uppermost Mississippian, upper Serpukhovian) in northern Spain near La Robla, and multiple aliquots have been meticulously prepared for distribution. The RA138 is characterised by variable U/Pb ratios (from ~1 to ~19) and a relatively high and homogeneous U content (~4 ppm). This material exhibits a low age uncertainty (0.2 %, 2s; unanchored, ID-TIMS), allowing for the establishment of a well-defined isochron, particularly when anchored to the initial Pb ratio using LA-ICP-MS. ID-TIMS analyses of micro drilled C1 cement (17 sub-samples) produce a lower intercept age of 321.99 ± 0.65 Ma, an initial 207Pb/206Pb ratio of 0.8495 ± 0.0065, and a Mean Square of Weighted Deviations (MSWD) of 5.1. The systematic uncertainty of 1.5 % observed in repeated LA-ICP-MS analyses challenges previous estimations of 2–2.5 % based on repeated analyses of ASH-15D and JT using WC-1 as primary reference material, underscoring the precision and reliability of RA138 for U-Pb dating applications.

Marcel Guillong, Elias Samankassou, Inigo A. Müller, Dawid Szymanowski, Nathan Looser, Lorenzo Tavazzani, Óscar Merino-Tomé, Juan R. Bahamonde, Yannick Buret, and Maria Ovtcharova

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2024-7', Greg Ludvigson, 01 Apr 2024
  • CC1: 'Comment on gchron-2024-7', Sota Niki, 07 Apr 2024
  • RC2: 'Comment on gchron-2024-7', Niki Sota, 09 Apr 2024
Marcel Guillong, Elias Samankassou, Inigo A. Müller, Dawid Szymanowski, Nathan Looser, Lorenzo Tavazzani, Óscar Merino-Tomé, Juan R. Bahamonde, Yannick Buret, and Maria Ovtcharova
Marcel Guillong, Elias Samankassou, Inigo A. Müller, Dawid Szymanowski, Nathan Looser, Lorenzo Tavazzani, Óscar Merino-Tomé, Juan R. Bahamonde, Yannick Buret, and Maria Ovtcharova

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Short summary
RA138 is a new reference material for U-Pb dating of carbonate samples via LA-ICP-MS. RA138 exhibits variable U/Pb ratios and consistent U content, resulting in a precise isochron with low uncertainty. ID-TIMS analyses fix a reference age of 321.99 ± 0.65 Ma. The observed systematic uncertainty challenges previous estimates. This research advances our ability to date carbonate samples accurately, providing deeper insights into geological processes and historical timelines.