Geochemical evidence for excess iron in the mantle beneath Hawaii |
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Authors: | Humayun Munir Qin Liping Norman Marc D |
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Institution: | Department of the Geophysical Sciences, 5734 South Ellis Avenue, Chicago, IL 60637, USA. humayun@magnet.fsu.edu |
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Abstract: | Chemical interaction of Earth's mantle with the liquid outer core should influence the mantle's iron content. Osmium isotope ratios in Hawaiian lavas indicate a mass flux of =1% core to the mantle, which is the immediate source of these lavas. We present precise measurements of the Fe/Mn ratio for Hawaiian lavas, revealing an increase of 1 to 2% in the mole fraction of iron in the mantle beneath Hawaii. This corresponds to a density anomaly of about 0.5%, about the same magnitude observed in seismic tomography models of the Pacific superswell region. These data also rule out a role for Mn-rich sediments as the source of the Hawaiian Os isotope signal. |
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