Host: Abstracts of Annual Meeting of the Geochemical Society of Japan
Name : Abstracts of Annual Meeting of the Geochemical Society of Japan
Number : 72
Date : September 07, 2025 - September 19, 2025
Pages 158-
The eucrite Juvinas is an important sample for which significantly different ages have been reported: 4562.5±1.0 Ma (Lugmair and Shukolyukov, 1998) and 4545.5±3.1 Ma (Yamashita et al., 2022). However, although Lugmair et al.'s reported age primarily depends on the Cr isotope ratios of chromite, detailed mineralogical descriptions have not been provided. To clarify the cause of this age discrepancy, we conducted mineralogical observations of chromite in Juvinas using Field Emission Scanning Electron Microscopy (FE-SEM). All observed chromites showed Mg# (=Mg/(Mg+Fe2+) atomic ratio multiplied by 100) values below 10, indicating that they are secondary metamorphic minerals. These findings raise significant questions about conventional interpretations of the ages obtained. In this presentation, we report these mineralogical observations and their implications for geochronology.
