Mantle melting versus mantle metasomatism

"the chicken or the egg" dilemma

Ekaterina S. Kiseeva*, Vadim S. Kamenetsky, Gregory M. Yaxley, Simon R. Shee

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Citations (Scopus)
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Abstract

Most eclogitic mantle xenoliths brought to the surface exhibit a certain degree of enrichment with incompatible elements, usually attributed to the effect of mantle metasomatism by a putative metasomatic fluid. The metasomatic overprint is represented mainly by enrichments in Na, K, Ba, Ti and LREE and the original source of this fluid remains unknown. In this paper, we present a detailed petrological study of a typical eclogitic mantle xenolith from the Roberts Victor kimberlite mine in South Africa. We find that its textural and mineralogical features present strong evidence for incipient melting. The melting assemblage we observe did not necessarily require introduction of additional components, that is: in-situ melting alone could produce highly incompatible element enriched melt without involvement of a hypothetical and speculative metasomatic event. Due to the higher abundance in incompatible elements and lower solidus temperature than peridotites, mantle eclogites, some of which represent previously subducted oceanic crust, are much more plausible sources of mantle metasomatism, but on the other hand, they can be considered as highly metasomatised themselves. This brings us to the chicken or egg dilemma - was the secondary mineral assemblage in mantle lithologies a result or a source of mantle metasomatism?

Original languageEnglish
Pages (from-to)120-130
Number of pages11
JournalChemical Geology
Volume455
DOIs
Publication statusPublished - 20 Apr 2017
Externally publishedYes

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Bibliographical note

Copyright the Author(s) 2016. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Carbonated eclogite
  • Cratonic mantle
  • Incipient melting
  • Kimberlite-borne xenolith
  • Roberts Victor
  • Secondary mineral assemblage

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