High-Mg carbonatitic melts in diamonds, kimberlites and the sub-continental lithosphere

Y. Weiss*, W. L. Griffin, D. R. Bell, O. Navon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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The trace elements of high-Mg carbonatitic high-density fluids (HDFs) trapped in six fibrous diamonds from Siberia exhibit patterns that are highly similar to those of Group I kimberlites, but are slightly more fractionated. The patterns of both are similar to the average pattern of post-Archaean xenoliths from the sub-continental lithospheric mantle (SCLM).The Siberian high-Mg carbonatitic HDFs are highly enriched in incompatible elements and have compositions comparable to those of high-Mg HDFs from Kankan, Guinea. However, in detail the latter show depletion of K, Rb, Cs, Nb and Ta and enrichment in Ba, Th, U and LREE relative to the Siberian HDFs. These differences correspond closely to those between the patterns of Group II and Group I kimberlites, respectively.Mixing, fractionation and melting were explored as possible scenarios to explain these similarities and to constrain the possible genetic relationships between HDFs, kimberlites and the SCLM. Addition of 2.5% of Group I kimberlitic magma or 0.5% of the Udachnaya high-Mg HDFs to a depleted peridotite closely reproduces the post-Archaean SCLM pattern. The formation of high-Mg HDFs through fractionation of kimberlitic magma calls for 80% crystallization of olivine, clinopyroxene, garnet, carbonate and ilmenite. However, mismatches in K, Rb, Y and Ho abundances, and absence of the postulated fractionating minerals as inclusions suggest other petrogenetic scenarios are more likely.High-Mg HDFs and kimberlites can be produced by melting of a common source. The pattern of the calculated source for Siberian HDF and Group I kimberlites resembles that of average post-Archean, rather than Archean, SCLM. Batch melting of such a source can produce high-Mg HDFs at 0.5% partial melting and Group I kimberlites at ~. 2%. Kankan HDFs and Group II kimberlites can be produced by 0.1 and 0.8% melting of average Archaean SCLM that carries phlogopite ± Fe-Ti oxides.The close correspondence between the trace-element composition of surface kimberlites and HDFs that were trapped at depth indicates that kimberlitic melts do not change their incompatible trace element contents much on their way to the surface (except for a possible loss of alkalis).The new data on the HDFs suggest a close genetic relation between high-Mg carbonatitic HDFs and kimberlites and reveals the similarity of the trace element of both to that of the post-Archaean SCLM. This similarity may reflect the interaction of such melts with the lithospheric keel, its melting to produce HDF and/or kimberlites or melting of deeper sources that led to formation of HDFs and kimberlite and to widespread metasomatism of the SCLM.

Original languageAmerican English
Pages (from-to)337-347
Number of pages11
JournalEarth and Planetary Science Letters
Issue number3-4
StatePublished - 15 Sep 2011

Bibliographical note

Funding Information:
We thank Suzi Elhlou and Norman Pearson for their advice with the LA-ICP-MS work, Ofra Klein-BenDavid for access and permission to use her unpublished data, Zvi Garfunkel for mentoring, ideas and discussions, Bill McDonough and John Gurney for suggestions and Sonja Aulbach and Graham Pearson for very constructive and helpful reviews. Research was funded by BSF grant 2004161 to Oded Navon and David Bell. This study used instrumentation funded by ARC LIEF and DEST Systemic Infrastructure Grants, Macquarie University and Industry. Y.W. thanks his good friends Arnon Brand and Uri Ryb for their bold spirit. This is contribution 767 from the Australian Research Council National Key Centre for the Geochemical Evolution and Metallogeny of Continents ( http://www.gemoc.mq.edu.au ).


  • Diamond
  • High-Mg carbonatitic HDFs
  • Kimberlite
  • Phlogopite
  • Sub-continental lithospheric mantle (SCLM)
  • Trace elements


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