Contributions to Mineralogy and Petrology

, Volume 140, Issue 1, pp 16–27

Kankan diamonds (Guinea) II: lower mantle inclusion parageneses

  • Thomas Stachel
  • Jeff W. Harris
  • Gerhard P. Brey
  • Werner Joswig
Article

DOI: 10.1007/s004100000174

Cite this article as:
Stachel, T., Harris, J., Brey, G. et al. Contrib Mineral Petrol (2000) 140: 16. doi:10.1007/s004100000174

Abstract

Frequent inclusions of ferropericlase, some coexisting with phases of MgSiO3, CaSiO3 and SiO2 composition, suggest that a large proportion of diamonds from Guinea are derived from the lower mantle. Low aluminium contents in MgSiO3 inclusions indicate derivation from the uppermost lower mantle, where Al solubility in perovskite is low. Trace element analyses (SIMS) of CaSiO3 inclusions reveal extreme degrees of LREE (200–2000 times chondritic) and Sr enrichment (70–1000 times chondritic) together with negative and positive Eu anomalies. This implies a highly enriched lower mantle source, possibly a product of a subducted oceanic slab. A number of phases that are only stable in the upper mantle are found to coexist with lower mantle phases and thereby indicate retrograde equilibration during slow exhumation within a rising plume or convection cell. In one case, however, an inclusion paragenesis of ferropericlase and olivine can be shown to have formed within the upper mantle, indicating that the occurrence of ferropericlase inclusions alone is an unreliable indicator of lower mantle origin.

Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Thomas Stachel
    • 1
  • Jeff W. Harris
    • 2
  • Gerhard P. Brey
    • 3
  • Werner Joswig
    • 3
  1. 1.Institut für Mineralogie, Universität Frankfurt, Senckenberganlage 28, 60054 Frankfurt, GermanyGermany
  2. 2.Division of Earth Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UKUK
  3. 3.Institut für Mineralogie, Universität Frankfurt, Senckenberganlage 28, 60054 Frankfurt, GermanyGermany

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