Research

Diamonds are unique in that they isolate inclusions of other minerals from diffusive exchange, even at mantle temperatures on a billion year time scale. This makes them near-perfect time capsules from the early history of continents. Steve's research is focused on determining the isotope systematics of different generations of lithospheric diamonds as a way to trace the evolution of subcontinental mantle that avoids the secondary effects seen in xenoliths. These studies have led to new insights into a global change in tectonic regime and the onset of modern-style plate tectonics between 3.2 and 3.0 billion years ago. Recent work on sublithospheric diamonds is aimed at elucidating the deep recycling of surficial components including boron, carbon and water back into the convecting mantle sampled by oceanic basalts.

Latest Publications

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1. Howarth, G.H., Kahle, B., Janney, P.E., Kahle, R., Du Plessis, A., Richardson, S.H. and Gurney, J.J., 2023. Caught in the act: Diamond growth and destruction in the continental lithosphere. Geology.
2. Howarth, G.H., Marsh, J.S., Duncan, A.R., Harris, C., Heinonen, J.S., Richardson, S.H., le Roex, A., Carlson, R.W. and Zartman, R.E., 2023. Petrogenesis of the Tuli Basin high-Ti picrites and basalts, Karoo CFB, southern Africa: Classification, stratigraphy, emplacement, and mantle source heterogeneity. Lithos, 440, p.107040.
3. Hartnady, M.I., Johnson, T.E., Schorn, S., Smithies, R.H., Kirkland, C.L. and Richardson, S.H., 2022. Fluid processes in the early Earth and the growth of continents. Earth and Planetary Science Letters, 594, p.117695.
4. Smit, K.V., Timmerman, S., Aulbach, S., Shirey, S.B., Richardson, S.H., Phillips, D. and Pearson, D.G., 2022. Geochronology of diamonds. Reviews in mineralogy and geochemistry, 88(1), pp.567-636.
5. Smith, E.M., Ni, P., Shirey, S.B., Richardson, S.H., Wang, W. and Shahar, A., 2021. Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances, 7(14), p.eabe9773.