Nitrogen isotopes in peridotitic diamonds from Fuxian, China: the mantle signature |
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Authors: | Pierre Cartigny,Stuart Boyd,Jeff. Harris,& Marc Javoy |
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Affiliation: | Laboratoire de Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, Universitéde Paris VII, et URA CNRS 1762, 4 Place Jussieu, 75251 Paris Cedex 05, France,;Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, Scotland, UK |
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Abstract: | Nitrogen isotopes in peridotitic diamonds from Fuxian, China, suggest that the upper mantle δ15N-value has been globally homogeneous since at least the Proterozoic (−5 to −8‰/ATM), with similar values for subcontinental and MORB mantle. In addition, Fuxian diamonds retain the memory of a primary nitrogen lower in δ15N (down to −25‰). For the first time δ15N- values in diamonds match those of enstatite chondrites, supporting a formation of the Earth from such meteorites and the idea of a heterogeneous accretion of the Earth's volatiles. Nitrogen concentrations in diamonds are believed to depend strongly on the rate of the diamond growth and not to be an indicator of C/N ratios of the fluids from which they grew. |
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