LA-ICPMS in-situ U-Pb dating of Ilmenite (FeTiO3)
Final Report Abstract
The Project, which explored the feasibility of U-Pb dating of metamorphic ilmenite by LA-ICPMS was successfully completed. The objective of the project was to apply the recently emerged method of U-Pb dating of low-U (<100 µg/g) minerals by LA-ICPMS to a set of well-characterized ilmenite-bearing samples, to investigate whether metamorphic ilmenite contains sufficient Uranium and 238U/206Pb variability to be successfully dated or not. In the course of the project, ten ilmenite-bearing samples from different localities and metamorphic grades were studied. Four of the samples contained either no Uranium or excess of non-radiogenic Pb, i.e. common Pb, and could not be dated. The remaining six samples were dateable. The obtained U-Pb dates are within uncertainty of previously published geochronometers from the same samples. As a summary, we can conclude that: i) metamorphic ilmenite can have sufficient U and 238U/206Pb variability to be dated by in-situ U-Pb LA-ICPMS techniques; ii) although the size of metamorphic ilmenites is relatively small (usually <100 µm), state-of-the-art equipment such as that available at FIERCE allows successful analysis of ilmenite, even with spot sizes of 26 µm; and iii) in accordance with the findings of Thompson et al. (2021), our study also indicates that using rutile as a matrix-matched material for normalising ilmenite analysis is a feasible approach. This project represents the first study to conduct U-Pb dating of metamorphic ilmenite. The success of the U-Pb dating of metamorphic ilmenite opens up the possibility of dating rocks that do not contain other traditional geochronometer (zircon, monazite), as well as low-grade metamorphic rocks. Likewise, this method provides a new tool for the multi-chronometer investigation of, e.g., orogenic processes that will provide a more complete understanding about their timing and duration.
Publications
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U-Pb dating of metamorphic Ilmenite by LA-ICPMS. Goldschmidt2023 abstracts. European Association of Geochemistry.
Beranoaguirre, Aratz; Millonig, Leo; Albert, Richard; Marschall, Horst & Gerdes, Axel
