Corundum-Hibonite Inclusions and the Environments of High Temperature Processing in the Early Solar System.

摘要

Calcium, Aluminum-rich inclusions (CAIs) are composed of the suite of minerals predicted to be the first to condense from a cooling gas of solar composition (1). Yet, the first phase to condense, corundum, is rare in CAIs, having mostly reacted to form hibonite followed by other phases at lower temperatures. Many CAIs show evidence of complex post-formational histories, including condensation, evaporation, and melting (e.g. 2, 3). However, the nature of these thermal events and the nebular environments in which they took place are poorly constrained. Some corundum and corundum-hibonite grains appear to have survived or avoided these complex CAI reprocessing events. Such ultra-refractory CAIs may provide a clearer record of the O isotopic composition of the Sun and the evolution of the O isotopic composition of the planet-forming region (4-6). Here we present in situ O and Mg isotopic analyses of two corundum/hibonite inclusions that record differing formation histories.