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

Abstract:

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.