Recovery of forsterite high-pressure polymorphs in gas gun shock-wave experiments

Hypervelocity impact experiments using a 30 mm, 2-stage light gas gun were performed to study the formation, rapid quench, and physical recovery of the olivine high-pressure(P) polymorphs wadsleyite and ringwoodite. A series of 3 tantalum impact experiments were performed over a range from 1.5 to 3 km/s to study the effects of increasing P and temperature(T) conditions on the formation and crystallization of these high-P phases. ALEGRA shock physics hydrocode was used to model shock wave propagation, P, T, and material conditions due to the impact. We utilize and expand upon both the steel recovery assembly and experimental processes detailed in Tschauner et al. (2009). These experiments are part of a larger campaign to expand the studied compositions from the pure Mg end member olivine forsterite to more Fe-enriched fayalitic compositions that are representative of what is observed and recovered in shocked meteorites. The main goal of this extended study is to constrain the incoherent olivine high-pressure phase formation mechanisms to better describe the shock history within meteorites. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.