Measurement of the Melting Curves of Mantle Materials and Their Geochemical Implications

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9508016 Heinz The high-temperature phase equilibria of mantle materials place many constraints upon the thermal structure of the Earth's deep interior. For instance, the melting curve of Fe-Mg silicate perovskite, which is believed to be the major mineral in the Earth's lower mantle, places a direct experimental bound on the temperature in the lower mantle since we know that the mantle is solid. The melting curve of Fe places a constraint on the temperature at the inner-outer core boundary, provided one can take into account the presence of a lighter alloying component. Melting curves of the major minerals from various laser heating laboratories are discrepant, and the differences need to be understood to be able to aprive at a consensus for the correct melting temperatures. New experiments using the thermal analysis technique in the laser-heated diamond anvil cell, developed at the University of Chicago, will be used to measure the melting curves of Fe-Mg silicate perovskite, a mixture of Fe-Mg silicate perovskite and magnesiowustite, iron, nickel ,FeO, and FeS to pressures on the order of 100 Gpa. it is hoped that the discrepancies, in the location of the melting curve in pressure temperature space, between various laboratories can be resolved. The melting curves of mantle minerals can be used to place geochemical constraints on the current state and evolution of the Earth's mantle.