Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 432, Issue -, Pages 374-380Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.epsl.2015.10.023
Keywords
diamonds; stable isotopes; subduction; majorite; stishovite
Categories
Funding
- Natural Environment Research Council [NE/J008583/1]
- EIMF [IMF512/2013]
- NERC [NE/J008583/1, IMF010001] Funding Source: UKRI
- Natural Environment Research Council [IMF010001, NE/J008583/1, 1108948] Funding Source: researchfish
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Sub-lithospheric diamonds from the Juina-5 and Collier-4 kimberlites and the Machado River alluvial deposit in Brazil have carbon isotopic compositions that co-vary with the oxygen isotopic compositions of their inclusions, which implies that they formed by a mixing process. The proposed model for this mixing process, based on interaction of slab-derived carbonate melt with reduced (carbide- or metal-bearing) ambient mantle, explains these isotopic observations. It is also consistent with the observed trace element chemistries of diamond inclusions from these localities and with the experimental phase relations of carbonated subducted crust. The O-18-enriched nature of the inclusions demonstrates that they incorporate material from crustal protoliths that previously interacted with seawater, thus confirming the subduction-related origin of superdeep diamonds. These samples also provide direct evidence of an isotopically anomalous reservoir in the deep (>= 350 km) mantle. (C) 2015 Elsevier B.V. All rights reserved.
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