Diamond, fluids and mantle metasomatism

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For scientists, diamond is not just another mineral. Its scientific value stems from the fact that diamond offers the deepest geochemical probe of the earth's interior. The exceptional chemical and physical properties of diamond allow it to store and preserve information about the deep mantle from where it originates. Diamond is also unique in that it occurs only in the most ancient, 2-3 billion year old segments of continents (i.e., cratons). Diamonds and their fluid and mineral inclusions record information about the mineralogy, composition and fluids percolating through the ancient lithospheric mantle. There are only 10 blocks of such stabilization older than 2.5 billion years in the world, and data on each of them provide invaluable insights into ancient geological processes and the formation of continents. The proposed research investigates how diamonds and diamondiferous melts are formed, and uses this information for constraints on the evolution of the proto-continents and their deep roots. Metasomatism is the physicochemical transformation of rocks driven by percolating fluid; metasomatism of the mantle may be a factor in diamond formation. Mantle fluids and gases are also crucial for generation of melts that entrain diamonds. I aim to constrain the nature and role of the metasomatic fluids in, both, diamond-forming processes and in magmatism affecting these proto-continents. The program will study several suites of diamonds, mantle xenoliths and diamondiferous rocks from Canadian and worldwide diamond deposits. Traditional analytical methods will include spectroscopic techniques, electron microanalysis, microscopy and mass-spectrometry. In addition, we will develop an innovative technique that will use X-ray diffraction for identification of micron-size minerals included in diamond hosts. This research will also provide important practical geological information to Canadian companies involved in diamond exploration.