A combined cathodoluminescence and electron backscatter diffraction examination of the growth relationships between Jwaneng diamonds and their eclogitic inclusions

Gareth R. Davies*, Quint van den Heuvel, Sergei Matveev, Martyn R. Drury, Ingrid L. Chinn, Michael U. Gress

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


To fully understand the implications of the compositional information recorded by inclusions in diamond it is vital to know if their growth was syn- or protogenetic and the extent to which they have equilibrated with diamond forming agents. The current paradigm is that the majority of inclusions in diamond are syngenetic but recently this assumption has been questioned. This study presents an integrated cathodoluminescence (CL) and electron backscatter diffraction (EBSD) study of 8 diamonds containing eclogitic inclusions: 19 pyrope-almandine garnets, 12 omphacitic clinopyroxenes, 4 sulphides, 1 coesite and 1 rutile from the Jwaneng diamond mine, Botswana. Diamond plates were sequentially polished to expose inclusions at different levels and CL imaging and EBSD were performed to constrain the relationship between diamond and inclusion growth. Despite complex growth and resorption, individual diamonds are single crystals with a homogeneous crystallographic orientation. All individual inclusions have homogeneous crystallographic orientation and no resolvable compositional zonation. The combined CL and EBSD data suggest that epitaxial inclusion-diamond growth is rare (none of 24 inclusions) and that the imposition of cubo-octahedral faces on inclusions does not necessarily result in epitaxy. Individual diamonds contain inclusions that record evidence of both syngentic and protogenetic relationships with the host diamond and in one case an inclusion appears syngenetic to the diamond core but protogenetic to the growth zone that surrounds 70% of the inclusion. These findings emphasise that inclusions in diamonds have multiple modes of origin and that in order to validate the significance of geochronological studies, further work is needed to establish that there is rapid chemical equilibration of protogenetic inclusions with diamond forming agents at mantle temperatures.

Original languageEnglish
Pages (from-to)231-242
Number of pages12
JournalMineralogy and Petrology
Issue numberSupplement 1
Early online date18 Sept 2018
Publication statusPublished - Dec 2018


Acknowledgements Debswana Diamond Company and The De Beers Group of Companies are thanked for allowing access to run of mine production and diamond donation. Gassan Diamonds and particularly Pieter Ouwerkerk are thanked for help with diamond polishing. Constructive reviews and comments by Jeff Harris and Fabrizio Nestola and guest editor Thomas Stachel are gratefully acknowledged. Travel for sampling was sponsored by Stichting dr Schűrmannfonds.

FundersFunder number
Stichting dr Schűrmannfonds


    • Diamond
    • Protogenetic
    • Silicate inclusion
    • Syngenetic


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