Journal article

Apatite compositions and groundmass mineralogy record divergent melt/fluid evolution trajectories in coherent kimberlites caused by differing emplacement mechanisms

Ashton Soltys, Andrea Giuliani, David Phillips



Kimberlites are pipe-like igneous bodies, consisting of a pyroclastic crater and diatreme, commonly underlain by coherent root-zone rocks, and with associated dyke/sill complexes. The processes that control the different modes of coherent kimberlite emplacement remain uncertain. In addition, late evolution of kimberlite melts during emplacement into the upper crust remains poorly constrained. Therefore, it is unclear whether there is a link between melt composition/evolution and the emplacement mechanism of coherent kimberlites (i.e. planar dykes/sills vs. irregular bodies in the root zone). An absence of comparative studies on late-stage magmatic phases across the different emplacement mode..

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Awarded by Swiss National Science Foundation

Funding Acknowledgements

We thank Graham Hutchinson for his tireless assistance during SEM and EPMA analysis at the University of Melbourne. We are grateful to Phillip Janney for facilitating access to the John J. Gurney Upper Mantle Room Collection (University of Cape Town), from which samples of the De Beers dyke were loaned. In addition, we thank the De Beers Group and Petra Diamonds for provision of additional samples and for allowing access to the Wesselton mine and Benfontein Farm for sample collection. Jock Robey organised access to various sites in the Kimberley area and supervised sample collection, for which we are exceptionally appreciative. We also thank Stephen Sparks for supplying samples of the Wesselton water tunnel sills. AS thanks Angus Fitzpayne, Hayden Dalton, Madeline Tovey, Lynton Jaques, Simon Shee, and Bruce Wyatt for fruitful discussions on kimberlite emplacement. AG acknowledges funding from the Swiss National Science Foundation (Ambizione grant n. PZ00P2_180126/1).