Tappert, R., Stachel, T., Harris, J., Muehlenbachs, K., Ludwig, T. and Brey, G.P. (2005) Subducting oceanic crust: The source of deep diamonds. Geology, 33, pp. 565-568. (doi: 10.1130/G21637.1)
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Abstract
Inclusions of majoritic garnet in diamonds from the Jagersfontein kimberlite formed at unusually great depths of ∼250 to >500 km in the asthenosphere and transition zone. The original host rocks were derived from a much shallower, basaltic (eclogitic) source. The presence of negative Eu anomalies in all majoritic garnets requires a crustal origin, thereby linking these very deep diamond sources to subducting oceanic crust. The carbon isotope values (δ13C) of the host diamonds fall within a narrow range at ∼−20‰, which is fundamentally different from the broad range (−24‰ to −2‰) and bimodal distribution of carbon isotopes of Jagersfontein diamonds that formed in the shallower lithosphere. This indicates that majoritic garnet-bearing diamonds at Jagersfontein inherited their light carbon isotopic composition directly from organic matter contained in a subducting slab. These diamonds were likely formed by direct conversion from graphite, well within the diamond stability field.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Harris, Dr Jeff |
| Authors: | Tappert, R., Stachel, T., Harris, J., Muehlenbachs, K., Ludwig, T., and Brey, G.P. |
| College/School: | College of Science and Engineering > School of Geographical and Earth Sciences |
| Journal Name: | Geology |
| ISSN: | 0091-7613 |
| ISSN (Online): | 1943-2682 |
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