Unusual noble gas compositions in polycrystalline diamonds: Preliminary results from the Jwaneng kimberlite, Botswana

Masahiko Honda*, David Phillips, Jeffrey W. Harris, Igor Yatsevich

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

We have undertaken noble gas analyses of four polycrystalline framesite diamonds from the Jwaneng kimberlite pipe, Botswana. These samples yielded complex, multiple noble gas components (crustal, atmospheric and in situ radiogenic/fissiogenic), which were successfully deconvoluted by combining vacuum crushing and step-heating experiments and examining a full suite of noble gas isotope and elemental abundances. The most striking observation is the presence of crustal nucleogenic neon, released on graphitisation of the framesites. Neon of this composition can only have been produced in the crust and subsequently incorporated during formation of the framesites in the mantle. This may indicate that noble gases produced in the crust, such as nucleogenic neon and possibly xenon, and some radiogenic 4He and 40Ar and fissiogenic xenon, were introduced into the subcontinental mantle source during ancient subduction-related processes. If correct, then some parts of the mantle may contain significant quantities of crustal noble gases.

Original languageEnglish
Pages (from-to)347-358
Number of pages12
JournalChemical Geology
Volume203
Issue number3-4
DOIs
Publication statusPublished - 16 Feb 2004
Externally publishedYes

Keywords

  • Diamond
  • Mantle evolution
  • Mantle lithosphere
  • Noble gas

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