Abstract. Ti 2p X-ray absorption spectra for a series of minerals have been measured. Crystal field multiplet calculations can explain the spectral shape. The asymmetry of the e. peak is shown to be related to distortions of the Ti Ir octahedron. It is found, theoretically as well as experimentally, that the absorption spectra are more sensitive to tetragonal distortions than to trigonal distortions. A number of silicate minerals and metamict minerals containing titanium are measured and Ti HI has not been observed in any of these minerals. A comparison is made to the 1 s X-ray absorption, and the potential of both for the study of minerals is discussed.

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Abstract. Members of the solid solution seriesZnl_xF%A1204 (x = 0.2, 0.4, 0.6 and 1.0) with spinel structure were synthesized by direct solid-state reaction of the simple metal oxides and metallic iron in evacuated silica ampoules at 1175 ~ C. Two aliquots of the single-phase spinels obtained for each composition were annealed under vacuum at 1075 ~ C and 725 ~ C for 48 hours and then quenched in liquid nitrogen.The cation distributions of all the quenched samples were determined by X-ray powder diffraction, using the Rietveld method of structural refinement. The degree of inversion increases with iron content and for spinels with the same chemical composition with quenching temperature. The relative areas estimated for the contributions to the M6ssbauer spectra of tetrahedrally-and octahedrally-coordinated Fe 2+ suggest that most of Zn 2+ cations remain at the tetrahedral site, as expected from the relative cation site preferences.Failure to quench the equilibrium cation distributions, suggested by deviations between the observed composition dependence of the cation distribution and that expected from the thermodynamic model of O'Neill and Navrotsky (1983, 1984), may be explained by an enhancement of cation diffusion rates in the Znl_xF%A1204 (0 < x < 1) spinels caused by the presence of cation vacancies. Fe3+/vacancy defects are easily formed in these spinels due to partial oxidation of Fe z+ at high temperature.