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Enhancement of cation diffusion rates across the 410-kilometer discontinuity in earth's mantle

, : Enhancement of cation diffusion rates across the 410-kilometer discontinuity in earth's mantle. Science 283(5400): 2-5

Rates of cation diffusion (magnesium, iron, and nickel) have been determined in olivine and its high-pressure polymorph, wadsleyite, at 9 to 15 gigapascals and 1,100[degree] to 1,400[degree]C for compositions that are relevant to Earth's mantle. Diffusion in olivine becomes strongly dependent on composition at high pressure. In wadsleyite, diffusion is one to two orders of magnitude faster than in olivine, depending on temperature. Homogenization of mantle heterogeneities (chemical mixing) and mineral transformations involving a magnesium-iron exchange will therefore occur considerably faster in transition zone than at depths of less than 410 kilometers. Copyright 1999 by the AAAS.


PMID: 9888846

DOI: 10.1126/science.283.5400.362

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