Diamond nitrogen isotopes

Kirkley MB, Gurney JJ, Otter ML, HiU SJ, Daniels LR (1991) The application of C-isotope measurements to the identification of the sources of C in diamonds. Appl Geochem 6 477 94 Kirshenbaum I, Smith JS, Crowell T, Graff J, McKee R (1947) Separation of the nitrogen isotopes by the exchange reaction between ammonia and solutions of ammonium nitrate. J Chem Phys 15 44(M46... 

Russell S. S., Arden 1. W., and Pillinger C. T. (1996) A carbon and nitrogen isotope study of diamond from primitive chondrites. Meteorit Planet. Sci. 31, 343-355. 

Bulanova G. P., Pearson D. G., Hauri E. H., and Griffin William L. (2002) Carbon and nitrogen isotope systematics within a sector-growth diamond from the Mir kimberlite, Yakutia. Chem. Geol. 188, 105-123. 

Cartigny P., Boyd S. R., Harris J. W., and Javoy M. (1997) Nitrogen isotopes in peridotitic diamonds from Fuxian, China the mantle signature. Terra Nova 9(4), 175—179. 

The nitrogen isotopic composition of the upper mantle has been estimated from MORE (Marty and Humbert, 1997 Marty and Zimmermann, 1999) and diamond (Javoy et ai, 1984 Cartigney et ai, 1998 Eoyd and Pillinger, 1994) data to be approximately = —4%c. Values as low as 515N = —25%o have been found in diamonds, indicating that there is another reservoir in the mantle. 

Nitrogen in the Archaean mantle The initial nitrogen isotopic composition of the Earth is not well known. However, nitrogen isotope measurements on 2.9-3.3 Ga diamonds from the subcontinental lithosphere have a mean S15N value of -5, and a similar C/N ratio to that of the modern mantle (Fig. 5.4), suggesting that there has been very little change since about 3.0 Ga (Marty Dauphas, 2003). 

Diamond pipes exhume samples of ancient rocks from 200 km depth beneath continents. Carbon and nitrogen isotopic anomalies in the diamonds and sulfur isotope anomalies within diamond inclusions provide evidence for ancient subduction and the existence of an ancient active surface biochemical cycle. Farquhar et al. [58] present data on 2.9 billion-year-old diamonds and a brief review of the literature on the topic. Given the rarity of diamond pipes, these data relate to the existence of processes and give little information on fluxes into the mantle. 

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