EXPERIMENTAL PETROLOGY OF THE LOWER MANTLE - A NATURAL PERIDOTITE TAKEN TO 54 GPA

The high‐pressure mineral assemblage produced from a natural peridotite sample (xMg = 0.897) has been synthesized in the laser‐heated diamond cell and identified by x‐ray diffraction at 54 GPa. Orthorhombic perovskite, (Mg,Fe)SiO3, magnesiowüstite, (Mg,Fe)O, and cubic perovskite, CaSiO3, are observed in estimated molar ratios of 1.00 : 0.46 : 0.08 (1.00 : 0.21 : 0.09 by volume) respectively, with no evidence of other phases being present. The lattice parameters measured at 54 GPa yield a density of 4.97(±0.03) Mg/m3 for the high pressure assemblage at 300 K, in good agreement with prior calculations of density for candidate lower mantle assemblages. Copyright 1990 by the American Geophysical Union.