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Mantle melting versus mantle metasomatism - “the chicken or the egg” dilemma


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Kiseeva, ES, Kamenetsky, VS ORCID: 0000-0002-2734-8790, Yaxley, GM and Shee, SR 2017 , 'Mantle melting versus mantle metasomatism - “the chicken or the egg” dilemma' , Chemical Geology, vol. 455 , pp. 120-130 , doi: 10.1016/j.chemgeo.2016.10.026.

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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?

Item Type: Article
Authors/Creators:Kiseeva, ES and Kamenetsky, VS and Yaxley, GM and Shee, SR
Keywords: kimberlite-borne xenolith, Roberts Victor, carbonated eclogite, incipient melting, cratonic mantle, secondary mineral assemblage
Journal or Publication Title: Chemical Geology
Publisher: Elsevier Science Bv
ISSN: 0009-2541
DOI / ID Number: 10.1016/j.chemgeo.2016.10.026
Copyright Information:

© 2016 The Authors. Published by Elsevier B.V. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

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