Episodic diamond growth beneath the Kaapvaal Craton at Jwaneng Mine, Botswana

Michael U. Gress*, Daniel Howell, Ingrid L. Chinn, Laura Speich, Simon C. Kohn, Quint van den Heuvel, Ellen Schulten, Anna S.M. Pals, Gareth R. Davies

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Important implications for the interior workings of the Earth can be drawn by studying diamonds and their inclusions. To better understand the timing and number of diamond forming events beneath the NW margin of the Kaapvaal Craton, a comprehensive reassessment of Jwaneng’s diamond populations has been undertaken. We report new inclusion abundance data from the visual examination of ~130,000 diamonds that validate the predominance of an eclogitic diamond suite (up to 88%) with on average 5% inclusion-bearing diamonds (with inclusions >10 μm in size). From this population, polished plates from 79 diamonds of eclogitic and peridotitic paragenesis have been studied with cathodoluminescence (CL) imaging and infrared spectroscopy (FTIR) traverses. The majority (80%) record major changes in N concentration and aggregation states, as well as sharp boundaries in the CL images of individual plates that are interpreted to demarcate discrete diamond growth events. In addition, bulk FTIR data have been acquired for 373 unpolished diamonds. Silicate inclusions sampled from distinct growth zones define 2 compositional groups of omphacites and pyrope-almandines associated with different N contents in their diamond hosts. These findings reinforce previous observations that at Jwaneng at least seven individual diamond forming events can be identified – 3 peridotitic and 4 eclogitic. The results demonstrate that detailed examination of diamond plates by CL imaging and FTIR traverses is necessary to unveil the complex history recorded in diamonds.

Original languageEnglish
Pages (from-to)219-229
Number of pages11
JournalMineralogy and Petrology
Issue numberSupplement 1
Early online date24 May 2018
Publication statusPublished - Dec 2018


Acknowledgements The authors sincerely thank Debswana and De Beers for providing access to run of mine production at DTCB and the generous supply of diamonds. Special thank goes to Samantha H. Perritt, Suzette Timmerman, Cas Nooitgedacht, Evalien A.S. van der Valk and Siem Peters who helped with the counting statistics, as well as the members of the Diamond Damage Management Department (DDMD) Tebogo Masire, Keletso Taolo and Robert Phiri accommodating us at DTCB and Onameditse Keitebetse for arranging the sample export. Travel for sampling was sponsored by Stichting Dr. Schurmannfonds. Thomas Stachel is thanked for providing access to the DeBeers Diamond Laboratory in Edmonton for FTIR analyses and to the diamond inclusion database, Sergei Matveev and Peter van Krieken for support with FTIR and EPMA in Utrecht, Frank J.C. Peeters for providing access to the EDF microscopy, Pieter Ouwerkerk and Gassan Diamonds BV for assistance in polishing. The manuscript benefitted from constructive comments of Fanus Viljoen, an anonymous expert, and editor Thomas Stachel.

FundersFunder number
Valk and Siem Peters


    • Cathodoluminescence
    • FTIR
    • Nitrogen aggregation
    • Silicate inclusions


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