1,2Robert W. Nicklas, 3,4Aratz Beranoaguirre, 2Dylan M. Seal, 5James M. D. Day, 2Ethan F. Baxter, 6Anthony B. Love
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70254]
1Lunar and Planetary Institute, USRA, Houston, Texas, USA
2Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts, USA
3Institut für Geowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
4Frankfurt Isotope and Element Research Center (FIERCE), Goethe-Universität Frankfurt, Frankfurt am Main, Germany
5Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
6Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina, USA
Published by arrangement with John Wiley & Sons
Brachinites and brachinite-like achondrites record melting processes at moreoxidizing conditions than many other achondrite meteorites, attested by relatively Fe-richsilicate phases. Here, new major-, trace-, and highly siderophile-element (Os, Ir, Ru, Pt, Pd,Re) abundances, as well as Re-Os and Rb-Sr isotope data are reported for the brachinite ElMedano 395 and for the anomalously apatite-rich (~1.26% modal) brachinite-like achondriteNorthwest Africa (NWA) 12,532. Both meteorites have Rb-Sr and Re-Os isotope systematicsthat have been significantly affected by terrestrial alteration, reflecting variable addition of Srand variable loss of Rb and Re. Brachinite-like achondrite NWA 12532 experienced lateaddition of metallic phases and apatite on its parent body, having nearly chondriticabundances of Os, Ir, Ru, Pt, and Pd. The apatite in NWA 12532 gives an age of4491.3 14.1 Ma, overlapping with apatite U-Pb ages for ordinary chondrites, as well asfor other brachinites and brachinite-like achondrites. This age is significantly younger thanavailable Mn-Cr ages for brachinite silicate phases. The young U-Pb ages of brachinites andbrachinite-like achondrites likely reflect significant impact shock resetting events at ~4.43 to4.49 Ga across the solar system, also recorded in ordinary chondrites. These resetting eventsmay be related to a significant dynamical reorganization at that time.
