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1 Earth and Atmospheric Sciences, University of Alberta, Edmonton T6G 2E3,
Canada
2 Institut für Mineralogie, Universität Frankfurt, 60054 Frankfurt,
Germany
3 Division of Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
Correspondence: E-mail: tstachel{at}ualberta.ca
Diamonds originate in the deep roots of ancient continental blocks (cratons) that extend into the diamond stability field beneath about 140 km. Over the last two decades, rare diamonds derived from even greater depths—the deep upper mantle, the transition zone (410-660 km), and the lower mantle—have been recognized. Inclusions in diamonds from the deep upper mantle and the transition zone document sources of basaltic composition, possibly related to subduction of old oceanic crust back into Earth's mantle. Diamonds from the lower mantle carry inclusions that largely confirm predictions of the composition and mineralogy of the deep mantle based on a "pyrolite" (primitive peridotitic) composition of silicate Earth. For some inclusions, however, the chemical evidence again points to a connection with subducting oceanic slabs, possibly ponding at the top of the lower mantle.
KEYWORDS: diamond inclusion, majorite, perovskite, phase transition, transition zone, lower mantle, subduction, megalith
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