Geophysics

Metallic melt for the mantle

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Science  11 Nov 2016:
Vol. 354, Issue 6313, pp. 717-718
DOI: 10.1126/science.354.6313.717-g

Ultralow velocity zones (ULVZs) are distinct and dense patches at the very base of Earth's rocky mantle. Liu et al. suggest that iron carbide may be a vital component of ULVZs on the basis of measurements of iron carbide melting temperatures. Iron carbides could form as iron and carbon exsolve from slabs subducting into the mantle. The high temperature near the base of the mantle could then lead to iron carbide melting and ponding in the ULVZ regions. If this hypothesis is correct, ULVZs are an unrecognized and important carbon reservoir within Earth.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1519540113 (2016).

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