Compressional behavior of omphacite to 47 GPa

摘要: Omphacite is an important mineral component of eclogite. Single-crystal synchrotron X-ray diffraction data on natural (Ca, Na) (Mg, Fe, Al)Si2O6 omphacite have been collected at the Advanced Photon Source beamlines 13-BM-C and 13-ID-D up to 47 GPa ambient temperature. Unit cell parameter crystal structure refinements were carried out constrain isothermal equation state compression mechanism. The third-order Birch–Murnaghan (BM3) fit all gives V 0 = 423.9(3) A3, K T0 = 116(2) GPa T0′ = 4.3(2). These elastic parameters are consistent with general trend diopside–jadeite join. eight-coordinated polyhedra (M2 M21) most compressible contribute majority unit compression, while SiO4 tetrahedra (Si1 Si2) behave as rigid structural units incompressible. Axial compressibilities determined by fitting linearized BM3 pressure dependences parameters. Throughout investigated range, b-axis more than c-axis. axial compressibility a-axis largest among three axes 0 GPa, yet it quickly drops smallest pressures above 5 GPa, which explained rotation stiffest major axis toward increase in pressure.