Stability of Fe, Al-bearing bridgmanite in the lower mantle and synthesis of pure Fe-bridgmanite.

L. Ismailova, E. Bykova, M. Bykov, V. Cerantola, C. McCammon, T. Boffa Ballaran, A. Bobrov, R. Sinmyo, N. Dubrovinskaia, K. Glazyrin, H.-P. Liermann, I. Kupenko, M. Hanfland, C. Prescher, V. Prakapenka, V. Svitlyk, L. Dubrovinsky

Science Advances (2016) 2, 7, e1600427; DOI: 10.1126/sciadv.1600427

The physical and chemical properties of Earth’s mantle, as well as its dynamics and evolution, heavily depend on the phase composition of the region. The lower mantle constitutes more than half of the Earth’s interior by volume and is believed to be dominated by a compound known as silicate perovskite (mineral name bridgmanite). Thus, bridgmanite’s properties are crucially important for understanding detailed structure and dynamics of the planet with a direct impact on life at the Earth’s surface ranging from deep-focus earthquakes to geochemical cycles which led to formation of mineral deposits.

On the basis of experiments in laser-heated diamond anvil cells, we demonstrate that Fe, Al-bearing bridgmanite is stable to pressures over 120 GPa and temperatures above 3000 K. Ferric iron stabilizes Fe-rich bridgmanite such that we were able to synthesize pure iron bridgmanite at pressures between ~45 and 110 GPa. The compressibility of ferric iron–bearing bridgmanite is significantly different from any known bridgmanite, which has direct implications for the interpretation of seismic tomography data.

A schematic picture of the Earth’s interior. On the right side – example of parts of the two-dimensional wide scan x-ray diffraction images of Fe,Al-bearing bridgmanite. On the left side – a polyhedral structural model of pure iron bridgmanite. Credits: Leyla Ismailova/ University of Bayreuth

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