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Low Core-Mantle Boundary Temperature Inferred from the Solidus of Pyrolite

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Science  31 Jan 2014:
Vol. 343, Issue 6170, pp. 522-525
DOI: 10.1126/science.1248186

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Melting Moments

The boundary between Earth's core and mantle defines where the iron-rich liquid outer core meets the more chemically heterogeneous solid lower mantle and is marked by a sharp thermal gradient of nearly 1500 kelvin. The precise relationship between temperature and melting of the lowermost mantle constrains the structure and heat flow across the core-mantle boundary. In order to identify trace amounts of liquid as melting initiates, Nomura et al. (p. 522, published online 16 January) performed x-ray microtomographic imaging of rocks of a primitive mantle composition that had been subjected to high pressures and temperatures in a diamond anvil cell. The experimentally determined maximum melting point of 3570 kelvin suggests that some phases typically thought to lose stability in the lowermost mantle, such as MgSiO3-rich post-perovskite, may be more widely distributed than expected.