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Science 5 June 1998:
Vol. 280. no. 5369, pp. 1570 - 1573
DOI: 10.1126/science.280.5369.1570
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Reports

Coupled 186Os and 187Os Evidence for Core-Mantle Interaction

Alan D. Brandon, * Richard J. Walker, John W. Morgan, Marc D. Norman, Hazel M. Prichard

Osmium isotopic analyses of picritic lavas from Hawaii show enrichments in the osmium-186/osmium-188 ratio (186Os/188Os) of 0.008 to 0.018%, relative to a chondritic upper mantle, that are positively correlated with enrichments in 187Os/188Os of 5.4 to 9.0%. The most viable mechanism to produce these coupled 186Os and 187Os enrichments is by addition of 0.5 to 1 weight percent of outer core metal to a portion of the D" layer and subsequent upwelling of the mixture. These data suggest that some plumes originate at the core-mantle boundary and that Os isotopes may be used to distinguish plumes derived from shallow versus deep mantle sources.

A. D. Brandon, R. J. Walker, J. W. Morgan, Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, USA.
J. W. Morgan, Department of Earth Resources, Colorado State University, Fort Collins, CO 80523, USA.
M. D. Norman, GEMOC, School of Earth Sciences, Macquarie University, NSW 2109, Australia.
H. M. Prichard, Department of Earth Sciences, University of Wales, Cardiff, CF1 3YE, United Kingdom.
*   To whom correspondence should be addressed. E-mail: brandon{at}geol.umd.edu

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