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UBC Theses and Dissertations

Crystal chemistry of the Olivines at elevated temperatures Lager, George Adolphe


Single crystal x-ray intensity data have been collected with a manual diffractometer utilizing flat-cone geometry for Ni-olivine, Ni₂SiO₄, (25°, 300°, 600° and 900°C), monticellite, Ca₁.₀₀Mg₀.₉₃Fe₀.₀₇SiO₄, (25°, 335°, 615° and 795°C) and giaucochroite, Ca₀.₉₈Mn₀.₈₇Mg₀.₁₀Zn₀.₀₅SiO₄ (25°, 300°, 600° and 800°C). Weighted anisotropic refinements resulted in residual (R) factors ranging from 0.026 to 0.045. Examination of these data together with data from high temperature refinements of forsterite (Smyth and Hazen, 1973), hortonolite (Brown and Prewitt, 1973) and fayalite (Smyth, 1975) indicates that the olivine structure expands primarily as a result of "bond length expansions in the non-tetrahedral sites. Three-dimensional strain theory has "been used to calculate the magnitude and directions of the principal axes of the thermal expansion ellipsoids for the polyhedra in the above olivines. The shapes and orientations of the thermal expansion ellipsoids for M(1) and M(2) octahedra are related to the topology and chemistry of the octahedra. The basic shape of the ellipsoid is a function of the structural configuration of the octahedron while its orientation is a function of the occupancy of the site. [the rest of the abstract can be found in the attached PDF file]

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