- 1Institut für Geowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany (beranoaguirre@fierce.uni-frankfurt.de)
- 2FIERCE - Frankfurt Isotope and Element Research Center, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
- 3Chair of Geochemistry & Economic Geology, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- 4Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria
- 5Geoscience Center, University of Göttingen, Göttingen, Germany
- 6Department of Geological Sciences, Stockholm University, Stockholm, Sweden
It is well known that the density of metamorphic reactions occurring in subduction zones, due to intense fluid-melt activity, is very high. One of the minerals resulting from all these reactions, present both in the downgoing slab and in the serpentinized mantle wedge, is magnetite. Its study is therefore crucial to understanding geodynamic processes, as it gives information about oxidized fluids, temperature, trace elements mobility etc... Its applicability encompasses not only metamorphic petrology (sensu lato) but also tectonic processes of accretion, exhumation and obduction (e.g., emplacement of the Samail Ophiolite), as well as ore geology, as it is an ubiquitous mineral in numerous ore deposit types. Being able to date magnetite, providing a temporal framework to all these reactions, is to put in one more piece of this big puzzle.
Advances in analytical techniques and instrumentation, above all regarding the laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), have made that currently, the U-Pb dating reaches far beyond the traditionally dated minerals (zircon, monazite, rutile, etc.). In this context, at the FIERCE laboratory of the Goethe University-Frankfurt, we have investigated the possibility of dating magnetite.
Magnetite from several localities (Greek Islands, Cyprus, Alps) have been studied, resulting in a variety of U and Pb contents (up to a few µg/g in the case of U) as well as a significant spread on the U/Pb ratios. This has allowed us to date the studied samples, with internal precisions as good as 1.5% in the best of the studied cases.
Recognising the possibility of dating such a mineral is only the first step in the implementation of the technique. Ideally, the availability of reference materials for magnetite analyses would be very advantageous. Currently (as of this EGU-abstract deadline), some of the samples dated by LA-ICPMS are being analysed using the U-Th/He method, which will allow us to compare the ages obtained by both methods and eventually, to use those magnetite as reference for future analyses.
How to cite: Beranoaguirre, A., Peillod, A., Patten, C., Dunkl, I., Hector, S., Ring, U., Kolb, J., and Gerdes, A.: First steps of LA-ICPMS U-Pb magnetite geochronology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16826, https://doi.org/10.5194/egusphere-egu25-16826, 2025.
