Abstract
CV3 Y-86009 carbonaceous chondrite is a breccia consisting of numerous clasts. Secondary fayalites (Fa>80) occur as grains (5-50 μm) and veins (∼10 × 50 μum) in the host matrix and most clasts. These fayalites show different abundances and Fa compositions in the host matrix and in each clast, and fayalite-veins terminate at the clast boundaries. Thus, the fayalites should have already formed in various conditions of aqueous alteration prior to the Y-86009 breccia formation. Mn-Cr isotope analysis was performed on 15 fayalites in the host matrix and clasts. An absolute age was determined to be 4560 Ma. This age is consistent with other CV3 fayalite formation ages. These results imply that all CV3 fayalites formed by aqueous alteration at the same time in the same single CV3 asteroid.
