%0 Journal article
%A Sinmyo, Ryosuke
%A Nakajima, Yoichi
%A McCammon, Catherine A.
%A Miyajima, Nobuyoshi
%A Petitgirard, Sylvain
%A Myhill, Robert
%A Dubrovinsky, Leonid
%A Frost, Daniel J.
%T Effect of Fe3+ on Phase Relations in the Lower Mantle: Implications for Redox Melting in Stagnant Slabs
%R 10.1029/2019JB017704
%R 10.23689/fidgeo-5139
%J Journal of Geophysical Research: Solid Earth
%V 124
%N 12

%X Recent studies have revealed that Earth's deep mantle may have a wider range of oxygen fugacities than previously thought. Such a large heterogeneity might be caused by material subducted into the deep mantle. However, high-pressure phase relations are poorly known in systems including Fe3+ at the top of the lower mantle, where the subducted slab may be stagnant. We therefore conducted high-pressure and high-temperature experiments using a multi-anvil apparatus to study the phase relations in a Fe3+-bearing system at 26 GPa and 1573–2073 K, at conditions prevailing at the top of the lower mantle. At temperatures below 1923 K, MgSiO3-rich bridgmanite, an Fe3+-rich oxide phase, and SiO2 coexist in the recovered sample. Quenched partial melt was observed above 1973 K, which is significantly lower than the solidus temperature of an equivalent Fe3+-free bulk composition. The partial melt obtained from the Fe3+-rich bulk composition has a higher iron content than coexisting bridgmanite, similar to the Fe2+-dominant system. The results suggest that strong mantle oxygen fugacity anomalies might alter the subsolidus and melting phase relations under lower mantle conditions. We conclude that (1) a small amount of melt may be generated from an Al-depleted region of a stagnant slab, such as subducted former banded-iron-formation, and (2) Fe3+ is not transported into the deep part of the lower mantle because of its incompatibility during melting.
%U http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/9485
%~  FID GEO-LEO e-docs