The composition and redox state of bridgmanite in the lower mantle as a function of oxygen fugacity

The Effect of Fe‐Al Substitution on the Crystal Structure of MgSiO3 Bridgmanite

“…This tendency for the amount of disproportionated metal to first increase and then decrease with pressure would mean that the f o 2 would also first decrease and then increase with pressure. As a result, the deep lower mantle maybe less reduced than the shallower region, although there is no reason to believe that the effect is sufficient for the f o 2 to be raised significantly above the IW buffer (Huang et al., 2021). Higher temperatures during magma ocean crystallization may have further suppressed the amount of metal formed through disproportionation due to the requirement for lower Fe 3+ contents in Brg in equilibrium with iron metal at these conditions (Boujibar et al., 2016; Frost et al., 2004; Huang et al., 2021).…”

“…As a result, the deep lower mantle maybe less reduced than the shallower region, although there is no reason to believe that the effect is sufficient for the f o 2 to be raised significantly above the IW buffer (Huang et al., 2021). Higher temperatures during magma ocean crystallization may have further suppressed the amount of metal formed through disproportionation due to the requirement for lower Fe 3+ contents in Brg in equilibrium with iron metal at these conditions (Boujibar et al., 2016; Frost et al., 2004; Huang et al., 2021). As indicated above, metal production may have then been further suppressed at pressures above 50 GPa, although removal of metal by core forming liquids as they pass through the shallow lower mantle remains a viable mechanism for mantle oxidation.…”

“…This tendency for the amount of disproportionated metal to first increase and then decrease with pressure would mean that the fo 2 would also first decrease and then increase with pressure. As a result, the deep lower mantle maybe less reduced than the shallower region, although there is no reason to believe that the effect is sufficient for the fo 2 to be raised significantly above the IW buffer (Huang et al, 2021).…”

Fe3+ -hosting carbon phases in the deep Earth

“…They conclude that the total iron content in silicate perovskite is controlled by aluminum in the silicate perovskite and its decrease is explained with the onset of the high spin to low spin transition in the ferropericlase at 70 GPa. However, in a recent study, Huang et al [44] emphasized the role of oxygen fugacity and typology of coexisting phases for iron partitioning in the lower mantle. As both of the phases with tetrahedrally coordinated carbon have shown to be stable at lower mantle conditions, they should be considered in the complex redox chemistry behind aluminium/magnesium exchange.…”

Pressure Destabilizes Oxygen Vacancies in Bridgmanite

“…Bridgmanite is stabilized in the pressure range 23–125 GPa (e.g., Ishii et al., 2018; Murakami et al., 2004) and is the dominant mineral in Earth (e.g., Irifune & Ringwood, 1987a, 1987b). It can incorporate large amounts of trivalent elements such as Al 3+ and Fe 3+ in its crystal structure (e.g., Andrault et al., 1998; McCammon, 1997; Navrotsky, 1999; Navrotsky et al., 2003; Shim et al., 2017) by the formation of XXO 3 and MgXO 2.5 components (X is Fe 3+ or Al 3+ ) via charge‐coupled and oxygen‐vacancy mechanisms, respectively (e.g., Huang, Boffa‐Ballaran, McCammon, Miyajima, Dolejš & Frost, 2021; Huang, Boffa‐Ballaran, McCammon, Miyajima, & Frost, 2021; Lauterbach et al., 2000; Liu, Akaogi, & Katsura, 2019; Liu, Ishii, & Katsura, 2017; Liu, Boffa‐Ballaran, et al., 2019; Liu et al., 2020; Navrotsky, 1999; Navrotsky et al., 2003; Nishio‐Hamane et al., 2005, 2008; O'Neill & Jeanloiz, 1994). The different substitution mechanisms thus produce different types of defect species.…”