Diamond carbon isotopes

Bottinga Y. (1969b). Carbon isotope fractionation between graphite, diamond and carbon dioxide. Earth Planet. Sci. Letters, 5 301-307. 

Fig. 3.5 Carbon isotope variations of diamonds (modified after Cartigny 2005)...

Deines P, Haggerty SE (2000) Small-scale oxygen isotope variations and petrochemistry of ultradeep (>300 km) and transition zone xenohths. Geochim Cosmochim Acta 64 117-131 Deines P, Gurney JJ, Harris JW (1984) Associated chemical and carbon isotopic composition variations in diamonds from Finsch and Premier Kimberhte, South Africa. Geochim Cosmochim Acta 48 325-342... 

Fig. 3.17. Carbon isotopic enrichment factors for aragonitic (dots) and calcitic (circles) foraminifera and inorganic precipitates as a function of temperature. Shown are the inorganic precipitate data of Baertschi (1957)- circle with dot Emrich et al. (1970)- large dots and Rubinson and Clayton (1969) revised - see text aragonite - solid diamond, calcite - hollow diamond. (After Grossman, 1984.)...

Much the same can be said about the diamonds, in that most minor and trace elements are radically anomalous. But the major element, carbon, has an isotopic composition within the range of solar-system normal. Moreover, the individual diamond grains are extremely small, characteristically only a few nanometers, and too small to support analysis even of carbon in individual grains. It may be that diamond carbon appears isotopically normal only because any isotopic analysis is an average over many grains. But because of the normal carbon there is persistent suspicion that most the diamonds are not really circumstellar or even presolar after all, and that the real presolar grain carrier is a small subset of the diamonds or some other phase entirely, less abundant than the diamonds but which follows them in the separation procedures. 

Pearson D. G., Davies G. R., Nixon P. H., and Mattey D. P. (1991b) A carbon isotope study of diamond facies pyroxenites and associated rocks from the Beni Bousera peridotite, north Morocco. In Orogenic Lherzolites and Mantle Processes, Spec. Vol. J. Petrol, (eds. M. A. Menzies, C. Dupuy, and A. Nicolas). Oxford University Press, Oxford, UK, pp. 175-189. 

The carbon isotopic composition of diamonds has been studied for many years (e.g., Galimov etal., 1978 Deines, 1980 Galimov, 1984). These early studies attempted to correlate diamond properties such as color and form with carbon isotopic composition in some form of classification... 

The carbon isotopic composition of diamonds has been explained by a variety of processes ... 

Carbon isotopic studies alone are not able to resolve the source of such carbon isotopic variability and the relative importance of these competing models. Thus, current approaches are to combine carbon isotopic studies with nitrogen abundance, aggregation, isotopic composition and even age determinations on the same diamonds (e.g., Hauri et al, 1999, 2002). 

Nearly all lower-mantle diamonds have such low nitrogen that they are classified type II (McCammon, 2001). These features are very distinctive from upper-mantle diamonds, which are chiefly type la and have widely variable percentages of A, A/B, and B centers. The carbon isotopic composition of ultradeep, lower-mantle diamonds is surprisingly homogeneous, most samples having typical upper-mantle values of... 

Figure 64 Comparison of the carbon isotopic composition of diamonds containing inclusions ascribed to transition zone and sublithospheric depths (TZ-UM clear) to diamonds with inclusions derived from lower mantle depths (LM gray). The number of specimens is given for each group (n = 132). Note that the —4 to —6 bar for lower mantle diamonds is off-scale at a number of 68. Transition zone and upper mantle diamonds are from these kimberlites Jagersfontein (6), Juina (1), KanKan (5), Orapa (1), Premier (1), and Sao Luiz (10). Lower mantle diamonds (and the number analyzed from each) are from these kimberlites Dokolwayo (1), DO-27 (5), Juina (30), KanKan (36), Koffiefontein (3), Letseng-la-Terai (1), and Sao Luiz (33) (sources Daniels and Gurney, 1999 Davies et al, 1999 Deines etal, 1989,1991a, 1993 Hutchison eta/., 1999 Kaminsky etal, 2001 McDade and Harris, 1999 ...

Cartigny P. (1998) Carbon isotopes in diamond. PhD Thesis, Universite de Paris VII. 

Deines P. (1980) The carbon isotopic composition of diamonds relationship to diamond shape, color, occurrence and vapor composition. Geochim. Cosmochim. Acta 44(7), 943-962. 

Deines P. and Harris J. W. (1995) Sulfide inclusion chemistry and carbon isotopes of African diamonds. Geochim. Cosmochim. Acta 59(15), 3173-3188. 

Deines P., Harris J. W., and Gurney J. J. (1987) Carbon isotopic composition, nitrogen content and inclusion composition of diamonds from the Roberts Victor Kimberlite, South Africa evidence for C depletion in the mantle. Geochim. Cosmochim. Acta 51, 1227-1243. 

Fitzsimons 1. C. W., Harte B., Chinn 1. L., Gurney J. J., and Taylor W. R. (1999) Extreme chemical variation in complex diamonds from George Creek, Colorado a SIMS study of carbon isotope composition and nitrogen abundance. Min. Mag. 63(6), 857-878. 

Galimov E. M., Kaminskiy F. V., and Ivanovskaya 1. N. (1978) Carbon isotope compositions of diamonds from the Urals, Timan, Sayan, the Ukraine, and elsewhere. Geochem. Int 15(2), 11-18. 

Harte B., Fitzsimons I. C. W., Harris J. W., and Otter M. L. (1999a) Carbon isotope ratios and nitrogen abundances in relation to cathodoluminescence characteristics for some diamonds from the Kaapvaal Province S. Africa. Mineral. Mag. 63(6), 829-856. 

Javoy M., Pineau F., and Demaiffe D. (1984) Nitrogen and carbon isotopic composition in the diamonds of Mbuji Mayi (Zaire). Earth Planet. Sci. Lett. 68(3), 399-412. 

Leech M. L. and Ernst W. G. (1998) Graphite pseudomorphs after diamond A carbon isotope and spectroscopic study of graphite cuboids from the Maksyutov complex, south Ural Mountains, Russia. Geochim. Cosmochim. Acta 62, 2143-2154. 

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