The shock compression molten silicate project will provide support for a graduate student who will learn and apply shock wave techniques toward understanding shock-induced melting of silicates at high pressure as well as researching dynamic compression of molten silicates over the pressure and temperature range existing in the Earth's mantle. Previously, our group has trained some 30 mineral physicists and high pressure researchers who have contributed their research, management, or teaching skills to scientific and technical efforts in government, industry, and academia. We propose to partially develop a new laser-based velocity projectile measurement system that is expected to provide a precise trigger signal at the time the projectile arrives at the target by extrapolating previous velocity history. The Ultra Low Velocity Zone (ULVZ) is a variable thickness 1 to 40 km zone of partially melted material lying at the base of the mantle underlying some low-velocity structures with horizontal dimensions of ~103 km. In these structures the S-wave velocity may be lowered by ~ 3% corresponding to 300K or more differences in lower mantle temperature. We propose to preheat samples to various initial temperatures (e.g. ~500 to 1500 K) so as to cross from the solid into the partially molten field at a range of temperatures and pressures. Thus, we will measure the longitudinal velocity to detect shock-induced melting of mantle minerals at pressures of 90 to 135 GPa and temperatures in the 3000 to 5000 degrees K range. Previously it has been demonstrated that silicate and oxide melting may be readily detected by a rapid drop in P-wave velocity upon melting. Moreover, upon encapsulating samples of silicates in molybdenum containers, Hugoniot data for molten silicates can be obtained. We propose to now extend previous data from the 40 GPa range upwards to 150 GPa and extend melting data for minerals such as MgSiO3 perovskite from 25 to 30 GPa where it is known from multi-anvil experiments up to 150 GPa.
