Reassessing the origin and chronology of the unique achondrite Asuka 881394: Implications for distribution of 26Al in the early Solar System

The achondrite Asuka 881394 has mineralogy broadly similar to that of eucrites but is isotopically, chemically and texturally distinct from them. Previous U-Pb chronology shows that it is very old; forming within the first 0.8 Ma of the formation of calcium-aluminum rich inclusions (CAIs). However, the age difference between Asuka 881394 and other very old Solar System materials (CAIs, quenched angrites) measured with the 26Al-26Mg and 53Mn-53Cr extinct radionuclide chronometers, and 207Pb/206Pb chronometer, is not the same. This could be interpreted to reflect heterogeneity in the distribution of 26Al and 53Mn in the early Solar System. Given the significant implications for the early Solar System chronology if 26Al and 53Mn are indeed heterogeneously distributed, in this study we further investigate the origin of Asuka 881394 and the apparent age discordance between short-lived and absolute chronometers, by focusing on measurement of its ε54Cr composition, renewed measurements of the absolute Pb-Pb age and new, high precision measurements of its 26Al-26Mg systematics