Superdeep Diamonds

✦ Optical photomicrograph of a large, gem-quality 'CLIPPIR' diamond showing shiny, linear, metallic inclusion and adjacent wing-shaped, black rosette fracture (photo: Evan Smith).

Superdeep diamonds are derived from below the continental lithosphere and most likely from the transition zone (670km deep) or the top of the lower mantle. A full understanding of their origins and the compositions of the high pressure mineral phases has potential to revolutionize our understanding of deep mantle circulation. The region of the mantle from which these diamonds are derived fills a critical gap in the modern mantle convection cycle known as plate tectonics. Oceanic lithosphere moves away from the ridge, ages, then subducts under arcs often, as seen by seismology, reaching into the lower

Relevant publications

Smith, E.M., Peng, N., Shirey, S.B., Richardson, SH., Wang, W., and Shahar, A. (2021) Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances 7: eabe9773 https://doi.org/10.1126/sciadv.abe9773

Shirey, S., Smit, K., Pearson, D., Walter, M., Aulbach, S., Brenker, F. E., Bureau, H., Burnham, A. D., Cartigny, P., Chacko, T., Frost, D. J. , Hauri, E. H., Jacob, D. E., Jacobsen, S. D., Kohn, S. C., Luth, R. W., Mikhail, S., Navon, O., Nestola, F., Nimis, P., Smith, E. M., Stachel, T., Stagno, V., Steele, A., Thomassot, E., Thomson, A. R., Weiss, Y. (2019) Diamonds and the Mantle Geodynamics of Carbon: Deep Mantle Carbon Evolution from the Diamond Record. In B. Orcutt, I. Daniel, & R. Dasgupta (Eds.), Deep Carbon: Past to Present (pp. 89-128). Cambridge: Cambridge University Press. doi:10.1017/9781108677950.005. https://www.cambridge.org/core/books/deep-carbon/diamonds-and-the-mantle-geodynamics-of-carbon/E46212484DDAA32B1DA14B796EB3D9BC

Smith, E. M., Shirey, S. B., Richardson, S.H., F. Nestola, F., Bullock, E. S., Wang, J. and Wang, W. (2019) Reply to: Evidence for two blue (type IIb) diamond populations, Nature 570, E28-E29, 2019. https://www.nature.com/articles/s41586-019-1246-8

Smith, E. M., Shirey, S. B., Richardson S. H., Nestola, F., Bullock, E. S., Wang, J., & Wang, W. (2018) Blue boron-bearing diamonds from Earth’s lower mantle. Nature, 560 (7716), 84–87. http://doi.org/10.1038/s41586-018-0334-5

Smit, K. V. and Shirey, S. B.​ (2018) Diamonds help solve the enigma of Earth's deep water, Gems & Gemology, Vol. 54 (no. 2) 220-223. https://www.gia.edu/doc/Summer-2018-Gems-Gemology.pdf

Smith, E. M., Shirey, S. B. & Wang, W. (2017) The very deep origin of the world's biggest diamonds. Gems and Gemology, Vol. 53, No. 4, pp. 388–403. https://www.gia.edu/gems-gemology/winter-2017-worlds-biggest-diamonds

Smith, E. M., Shirey, S. B., Nestola, F., Bullock, E. S., Wang, J., Richardson Stephen, H., & Wang, W. (2016) Large gem diamonds from metallic liquid in Earth’s deep mantle. Science, 354, 1403–1405. http://doi.org/10.1126/science.aal1303

Shirey, S.B., and Shigley, J.E. (2013) Recent advances in understanding the geology of diamonds: Gems and Gemology, v. 49, 188–222. http://dx.doi.org/10.5741/GEMS.49.4.188

Shirey, S.B., Cartigny, P., Frost, D.J., Keshav, S., Nestola, F., Nimis, P., Pearson, D.G., Sobolev, N.V., and Walter, M.J. (2013) Diamonds and the Geology of Mantle Carbon: Reviews in Mineralogy and Geochemistry, v. 75, p. 355–421. http://doi.org/10.2138/rmg.2013.75.12

Walter, M. J., Kohn, S. C., Araujo, D., Bulanova, G. P., Smith, C. B., Gaillou, E., et al. (2011) Deep Mantle Cycling of Oceanic Crust: Evidence from Diamonds and Their Mineral Inclusions. Science, 334, 54–57. http://doi.org/10.1126/science.1209300

Harte, B. (2011) Diamond Window into the Lower Mantle. Science, 334, 51–52. http://doi.org/10.1126/science.1213012

Pearson, D.G., Canil, D., and Shirey, S.B. (2003) Chapter 7 - Mantle samples included in volcanic rocks: xenoliths and diamonds, in Carlson, R.W., ed., Teatise On Geochemistry: Vol. 2, The Mantle: New York, Elsevier, p. 171-277. https://www.sciencedirect.com/science/article/pii/B0080437516020053?via%3Dihub