Titanium minerals and their assemblages in the Earth’s mantle: A review of natural and experimental data

A review of the data available on the composition and abundance of titanium-bearing phases in the Earth’s mantle is provided in the paper. The main attention is paid to the discussion of natural minerals: the patterns of the mineralogy of mantle titanium-bearing phases (rutile, FeTiO3 ilmenite, garnet, pyroxene, spinel and post-spinel phases, phases with ilmenite- and perovskite-type structures, armalcolite) are given, the likely mechanisms of titanium incorporation into mantle phases, as well as the limiting titanium concentrations in these phases are considered. The new experimental data on the composition and conditions of the formation of titanium-bearing minerals and their phase associations at different mantle depths is generalized: phase relations in Ti-bearing systems (MgO–SiO2–TiO2 ± Al2O3) and the influence of titanium on the parameters of the most important phase transformations under the conditions of the mantle are considered. Agreement of the experimental results with the natural data allows us to clarify the patterns of the interphase titanium partitioning and the minor-element composition of the Earth’s deep geospheres.