The thermal equation of state of FeTiO3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures

Abstract

We present in situ measurements of the unit-cell volume of a natural terrestrial ilmenite (Jagersfontein mine, South Africa) and a synthetic reduced ilmenite (FeTiO 3 ) at simultaneous high pressure and high temperature up to 16 GPa and 1273 K. Unit-cell volumes were determined using energy-dispersive synchrotron X-ray diffraction in a multi-anvil press. Mössbauer analyses show that the synthetic sample contained insignificant amounts of Fe 3+ both before and after the experiment. Results were fit to BirchMurnaghan thermal equations of state, which reproduce the experimental data to within 0.5 and 0.7 GPa for the synthetic and natural samples, respectively. At ambient conditions, the unit-cell volume of the natural sample [V 0 = 314.75 ± 0.23 (1σ) Å 3 ] is significantly smaller than that of the synthetic sample [V 0 = 319.12 ± 0.26 Å 3 ]. The difference can be attributed to the presence of impurities and Fe 3+ in the natural sample. The 1 bar isothermal bulk moduli K T0 for the reduced ilmenite is slightly larger than for the natural ilmenite (181 ± 7 and 165 ± 6 GPa, respectively), with pressure derivatives K 0 ′ = 3 ± 1. Our results, combined with literature data, suggest that the unit-cell volume of reduced ilmenite is significantly larger than that of oxidized ilmenite, whereas their thermoelastic parameters are similar. Our data provide more appropriate input parameters for thermo-chemical models of lunar interior evolution, in which reduced ilmenite plays a critical role.

Trace element partitioning between ilmenite, armalcolite and anhydrous silicate melt: Implications for the formation of lunar high-Ti mare basalts

“…Draper and van Westrenen, 2007;van Westrenen and Draper, 2007) and are consistent with the measured decreases in the Mg/Fe site volumes with increasing compression (e.g. Tronche et al, 2010). Although decreases in r 0 are often accompanied by increases in E, interpreting E values is notoriously difficult (e.g.…”

“…Their presence at relatively shallow levels combined with their relatively high density (e.g. Tronche et al, 2010) is thought to have resulted in a gravitationally unstable mineral stratification in the lunar mantle, inducing a mantle overturn that triggered significant mare basalt formation (e.g. Elkins-Tanton et al, 2002;Hess and Parmentier, 1995;de Vries et al, 2010).…”

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

“…The same procedure was applied to an inclusion of ilmenite in specimen GRR1507 (Table 1, Fig. S4a) using the equation of state for natural ilmenite of similar composition (47). The results give entrapment conditions in the same pressuretemperature interval as ice-VII from the same host diamond GRR1507 (Fig.…”

Structural, electronic and elastic properties of FeBO3(B = Ti, Sn, Si, Zr) ilmenite: a density functional theory study

“…148) space group, where the anions are densely packed in a hexagonal array with cations occupying twothirds of the possible octahedral sites in an alternating arrangement enabling the sharing of the octahedron AO 6 edges. 6,7 This material can also take the structure of other polymorphs (LiNbO 3 , perovskite) depending on the pressure conditions. Furthermore, the cations structural distribution enables charge transfer between the octahedral altering the valence states of the metals (Fe 2+ Ti 4+ 4 Fe 3+ Ti 3+ ) under extreme pressure conditions.…”