A Petrographic and MG Isotopic Study of CAI in BALI (C3V) and Coolidge (C4V)

One of the least well understood and most controversial aspects of CAI is the degree to which their mineralogical, chemical and isotopic composition has been affected by alteration and metamorphism. Coolidge is a highly metamorphosed carbonaceous chondrite, the only C4V (Van Schmus, 1969) and we have begun a petrographic and Mg isotopic study of Coolidge CAI to investigate the extent of chemical and isotopic reequilibration during thermal metamorphism. We also present the first Mg isotopic results from a coarse-grained CAI from Bali (C3V).