La Tourrette This project consists of a series of laboratory experiments designed to measure the rates of self diffusion in minerals found in refractory inclusions and chondrules in undifferentiated meteorites. These inclusions commonly preserve primordial isotopic and chemical disequilibrium amongst coexisting phases, which requires that they were never subsequently heated to the point where they could re-equilibrate through diffusive exchange. Thus, many meteorite inclusions retain crucial clues about their thermal histories. The goal of this work is to experimentally calibrate the conditions under which isotopic heterogeneities found in these inclusions can be preserved. The principal focus of the experiments will be Mg diffusion in anorthite, melilite, and hibonite to assess the preservation of 26Mg anomalies produced by the decay of 26Al. Additional measurements of Ca and Ti diffusivities in hibonite, pyroxene, and melilite will help refine the thermal constraints. The results will be combined with planetary formation models to help constrain the size distribution, assembly timescales, and thermal histories of early planetesimals into which these object were included. Natural and synthetic single crystals will be annealed at 1 atm pressure and diffusion profiles measured by SIMS.
