20-EPN2-074: Titanium and chromium isotopes in individual chondrules and anomalous clasts in chondrite meteorites
Visit by Philip Reger, University of Western Ontario (Canada) to TA2.14 ETH Zurich Geo- and Cosmochemistry Isotope Facility (Switzerland).
Dates of visit: 5-22 July 2021
Report Summary: Chondrules, which are sub-millimetre igneous spherules and the main component of chondrites, formed during the first 5 Myr of the Solar System. Both 26Al-26Mg and 207Pb-206Pb ages of individual chondrules have also shown a ~2 Myr age difference between them in single meteorites. To advance our understanding of chondrule formation and the evolution of the protoplanetary disk within its first 5 Myr of existence, we proposed to obtain the mass-independent isotopic compositions of Cr and Ti for 6 selected chondrules and anomalous clasts from H and L ordinary chondrites. During the Europlanet TA visit, the Cr isotope compositions were analyzed by MC-ICP-MS after undergoing Cr and Ti separation by ion-exchange chromatography (awaiting mass spectrometry measurements for Ti). The Cr isotopic analyses are the most precise results from individual chondrules to date and show variability of the Cr isotope composition in individual chondrules, even within the same meteorite. A comparison of ε54Cr with chronological data previously obtained on the same chondrules suggests that the Cr isotope composition of the inner Solar System (NC reservoir) underwent a gradual change during at least the first 2 Myr of the Solar System. This change could potentially reflect thermal processing, a change of infalling molecular cloud material, or the decreasing incorporation of refractory minerals without 54Cr excesses into chondrule precursors.