Journal Article

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

L. H. Pilbeam, T. F. D. Nielsen and T. E. Waight

in Journal of Petrology

Volume 54, issue 7, pages 1399-1425
Published in print July 2013 | ISSN: 0022-3530
Published online April 2013 | e-ISSN: 1460-2415 | DOI: https://dx.doi.org/10.1093/petrology/egt016
Digestion Fractional Crystallization (DFC): an Important Process in the Genesis of Kimberlites. Evidence from Olivine in the Majuagaa Kimberlite, Southern West Greenland

Show Summary Details

Preview

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.

Keywords: kimberlite; carbonatite; olivine; orthopyroxene; crystallization

Journal Article.  14044 words.  Illustrated.

Subjects: Petrology

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content. subscribe or login to access all content.