Mantle diamonds

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 ...

Lower-mantle diamonds are characterized by restricted and heavier, mantle-like This... 

B. (1997) A new tetragonal silicate mineral occurring as inclusions in lower-mantle diamonds. Nature (London) 387(6632), 486-488. 

Hutchison M. T., Cartigny P., and Harris J. W. (1999) Carbon and nitrogen compositions and physical characteristics of transition zone and lower mantle diamonds from Sao Luiz, Brazil. In The J. B. Dawson Volume Proceedings of the Vllth International Kimberlite Conference (eds. J. J. Gurney, J. L. Gurney, M. D. Pascoe, and S. H. Richardson), Red Root Designs, Cape Town, vol. 1, pp. 372-382. 

Hayman, P.C., Kopylova, M.G., and Kaminsky, F.V., 2005. Lower mantle diamonds from Rio Soriso (Juina area, Mato Grosso, Brazil). Contrib. Mineral. Petrol., 149, 430-45. 

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