Properties of Mantle Minerals (Rocks)

Mantle minerals are among the most complex alloys, involving strongly correlated magnetic end members. Outstanding examples are the most abundant phases of the Earth's lower mantle (Mg(1-x),Fex)SiO3-perovskite and (Mg(1-y),Fey)O, magnesiumwustite. An additional complication is the change in magnetic state of iron under pressure in certain sites. High-to-low spin transitions in iron are found in these minerals at pressures corresponding to mid-mantle. They alter the partitioning of Fe between them, most likely increasing y/x. But the transition pressure is concentration dependent providing a negative feedback to the spin transition. Understanding this complex phenomenon is fundamental to understanding the nature of the lower mantle. The first step is to address two classes of materials problems: solid solutions and the behavior of the strongly correlated iron sites under pressure. The next step involves phase equilibrium, thermoelastic, and transport properties for single and multi-phase aggregates.

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