Compressional behavior of select mantle silicates

Single crystal diffraction is the most direct method to determine the sample's crystal structure. From single crystal diffraction data, people can determine the sample's structural parameters such as lattice parameters, polyhedral volume and distortion, bond length, bond angle, atomic displacement parameter, etc. With the recent developments in diamond anvil cell techniques, it is possible now to collect single crystal diffraction data up to Earth's mantle and core pressures. By measuring mineral's crystal structure at high pressure, one can constrain equation of state and elastic anisotropy, both of which are important for seismological and geodynamical modeling of the Earth's deep interior. In this study, we present results of recent high pressure single crystal diffraction studies on the compressional behaviors of omphacite ((Ca, Na)(Mg, Fe, Al)Si2O6) and libenbergite (Ni2SiO4). Omphacite is one of the major minerals of ecologite, which is among the main components of subducted slabs. Our study on the compressional behavior of omphacite up to 47 GPa provides important constraints on the elasticity of subducting slabs. Libenbergite is the nickel-bearing end-member of olivine, which is the most abundant mineral of the upper mantle. Our measurements on the compression of libenbergite up to 42 GPa will help people understand the behavior of nickel-bearing minerals at the upper mantle conditions. Both experiments were carried out at the Partnership for eXtreme Xtallography (PX2) program, which is dedicated to high pressure single crystal diffraction research at the Advanced Photon Source. With these two experiments, we would like to demonstrate the experimental capabilities of the PX2 program.