9305219 Bass This award supports a 2-year collaborative research program intended to elucidate the elastic properties of majorite, the garnet-structured high-pressure phase of pyroxene that is an important constituent of the transition zone in the Earth's mantle. The study would check previous measurements that are controversial, resolving whether or not the properties of majorite are anomalously sensitive to details of composition, crystallographic structure, ordering or origin. Resolving this issue is critical to understanding the geophysical properties of the mantle transition zone. The work would also provide a significant cross-check between two laboratories and between two methods of determining elastic properties on polycrystalline aggregates, Brillouin spectroscopy and static compression. For the first time, natural samples of transition-zone high-pressure phases would be made available to the community for complementary studies through modern techniques of chemical and physical micro- analysis. ***
