Stability of ferropericlase in the lower mantle

We have heated ferropericlases (Mg0.60Fe0.40)O and (Mg0.50Fe0.50)O to tempe ratures of 1000 kelvin at pressures of 86 gigapascals, simulating the stabi lity of the solid solution at physical conditions relevant to Earth's lower mantle. The in situ x-ray study of the externally heated samples in a Mao- Bell-type diamond anvil cell shows that ferropericlase may dissociate into magnesium-rich and iron-rich oxide components. The result is important beca use the decomposition of ferropericlase into Lighter and heavier phases wil l cause dynamic effects that could lead to mantle heterogeneity.