High-Pressure Melting of Pyroxenite: Implications for Deep Mantle Melting

The Earth's bulk composition is fundamental to understanding the formation and evolution of Earth. Our experiments aim to investigate the behavior of Earth's mantle at high pressures and temperatures, so that we may better understand the current state of Earth's mantle, and its thermochemical evolution over time. Our samples consist of a synthetic pyroxenite mix (MIX1G, Hirschmann et al., 2003), a bulk composition that may represent the parent source of ocean island basalts (OIB). We use a laser-heated diamond-anvil cell (LHDAC) in order to melt pyroxenite at the lower mantle pressures, in conjunction with 4-color temperature mapping and electron microscopy of quenched samples in cross section. We find that at pressures between 35 and 55 GPa, the solidus phase changes from silicate to oxide, consistent with melting of a peridotite mantle.