01 Apr 2022
01 Apr 2022
Status: this preprint is open for discussion.

In-situ LA-ICPMS U-Pb dating of Sulfates: Applicability of carbonate reference materials as matrix-matched standards

Aratz Beranoaguirre1,2,3,4, Iuliana Vasiliev5, and Axel Gerdes2,3 Aratz Beranoaguirre et al.
  • 1Institut für Angewandte Geowissenschaften, Karlsruher Institut für Technologie, Adenauerring 20 b, 76131 Karlsruhe, Germany
  • 2Institut für Geowissenschaften, Goethe-Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
  • 3Frankfurt Isotope and Element Research Center (FIERCE), Goethe-Universität Frankfurt, Frankfurt am Main, Germany
  • 4Geologia Saila, Euskal Herriko Unibertsitatea UPV/EHU, Sarriena z/g, 48940 Leioa, Spain
  • 5Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325 Frankfurt am Main, Germany

Abstract. Recent developments on analytical capabilities in the field of in situ laser ablation mass spectrometry (LA-ICPMS) have expanded the applications of U-Pb geochronometers in low-U minerals such as carbonates or garnets. Although the rapid evolution of the technique relies on well characterized matrix-matched reference materials, the use of non-matrix-matched standards has been evaluated given the unavailability of standards for some minerals. In this article, we explore the suitability of using carbonate as reference materials for in situ U-Pb dating of sulfates. We have used the astrochronologically dated gypsum and anhydrite samples deposited during the Messinian Salinity Crisis (5.97–5.33 Ma) and compared these dates with the U-Pb ages obtained by LA-ICPMS. Although the majority of the samples failed due to the elevated common-Pb content and low 238U / 204Pb ratios, five of the samples showed a higher dispersion on U / Pb ratios. The obtained dates in four of these samples are comparable with the expected ages while another gave an unexpected younger age, each of them with 6–11 % of uncertainty. The pit depth of the spots showed that the sulfates ablate faster than carbonates, but the offset due to the crater geometry mismatch or downhole fractionation is not noticeable. To sum up, the bias between the U-Pb and expected cyclostratigraphic ages, if any, is included in the uncertainty and thus, the results obtained here suggest that carbonate reference materials are reliable for in situ U-Pb dating of sulfates.

Aratz Beranoaguirre et al.

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Aratz Beranoaguirre et al.

Aratz Beranoaguirre et al.

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Latest update: 03 Apr 2022
Short summary
The U-Pb dating by in situ laser ablation mass spectrometry (LA-ICPMS) technique requires reference materials of the same nature as the samples to be analysed. Here, we have explored the suitability of using carbonate materials as reference for sulfates, since there is no sulfate reference material. The results we obtained are satisfactory and thus, from now on, the sulfates can also be analysed.