Digestion Fractional Crystallization (DFC): an Important Process in the Genesis of Kimberlites. Evidence from Olivine in the Majuagaa Kimberlite, Southern West Greenland

Pilbeam, L. H. and Nielsen, T. F. D. and Waight, T. E. (2013) Digestion Fractional Crystallization (DFC): an Important Process in the Genesis of Kimberlites. Evidence from Olivine in the Majuagaa Kimberlite, Southern West Greenland. Journal of Petrology, 54 (7). pp. 1399-1425. ISSN Print ISSN 0022-3530 - Online ISSN 1460-2415 DOI https://doi.org/10.1093/petrology/egt016

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Abstract

High-precision electron microprobe data for major and trace elements (nickel, calcium and manganese) in the margins and rims of groundmass olivine grains from the Majuagaa kimberlite (sensu stricto) in southern West Greenland are presented. Despite a range of olivine core compositions defining several zoning types most of the olivine grains have similar margins. The olivine cores are considered to be xenocrysts in the kimberlite magma whereas the margins represent cognate olivine crystallized from the kimberlite melt itself. We evaluate models of olivine margin formation by fractional crystallization, fractional crystallization with simultaneous digestion of xenoliths, and diffusion. Only fractional crystallization coupled with digestion of xenocrysts (primarily orthopyroxene), with subsequent minor diffusion, can account for the observed compositional profiles in the olivine margins. We propose that the digestion crystallization process, whereby the entrained xenolithic material reacts with the kimberlite melt, is important in the evolution of kimberlite magmas. We suggest that this type of reaction gives a distinct local flavour to the parental kimberlite melt and can account for the similarities and differences between the various kimberlitic (sensu lato) magma types present in southern West Greenland and worldwide.

Item Type:	Article
Uncontrolled Keywords:	2013AREP; IA65;
Subjects:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title:	Journal of Petrology
Volume:	54
Page Range:	pp. 1399-1425
Identification Number:	https://doi.org/10.1093/petrology/egt016
Depositing User:	Sarah Humbert
Date Deposited:	03 May 2013 17:21
Last Modified:	14 Nov 2013 17:56
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2760

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