Nitrogen isotopes in peridotitic diamonds from Fuxian, China: The mantle signature

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.