Diamond, subcalcic garnet, and mantle metasomatism: Kimberlite sampling patterns define the link

V. G. Malkovets, W. L. Griffin, S. Y. O'Reilly, B. J. Wood

Research output: Contribution to journalArticle

83 Citations (Scopus)

Abstract

A genetic relationship between diamond and subcalcic Cr-pyrope garnet, both being produced by a metasomatic process, can be inferred from the sampling patterns of kimberlites in the Daldyn-Alakit province, Yakutia, Russia. Pressure-temperature estimates for xenoliths and xenocrysts show a strong concentration of highly depleted rocks in a well-defined zone 140-190 km deep; diamond inclusions and diamond-bearing xenoliths show that most diamonds come from harzburgites within this layer. Xenocryst distribution curves indicate that diamondiferous kimberlites have sampled both garnet and chromite from the harzburgitic layer, but low-grade pipes have sampled only chromite. Diamond formation probably is due to the oxidation of methane-rich, silica-bearing fluids: Fe2O3 (in chromite) + CH4 → C + H2O + FeO (in chromite), accompanied by another reaction: chromite ± olivine ± orthopyroxene + Si, Ca (in fluid) → low-Ca, high-Cr garnet. The presence or absence of diamond in kimberlites thus reflects the distribution of metasomatized fluid conduits in a lithosphexic mantle that originally consisted of highly refractory harzburgites containing neither garnet nor diamond.

Original languageEnglish
Pages (from-to)339-342
Number of pages4
JournalGeology
Volume35
Issue number4
DOIs
Publication statusPublished - Apr 2007
Externally publishedYes

Fingerprint

kimberlite
metasomatism
diamond
garnet
chromite
mantle
sampling
fluid
pyrope
orthopyroxene
olivine
pipe
silica
methane
oxidation
rock

Keywords

  • Archean mantle
  • Diamond genesis
  • Mantle harzburgite
  • Mantle metasomatism
  • Subcalcic garnet

ASJC Scopus subject areas

  • Geology

Cite this

Malkovets, V. G., Griffin, W. L., O'Reilly, S. Y., & Wood, B. J. (2007). Diamond, subcalcic garnet, and mantle metasomatism: Kimberlite sampling patterns define the link. Geology, 35(4), 339-342. https://doi.org/10.1130/G23092A.1

Diamond, subcalcic garnet, and mantle metasomatism : Kimberlite sampling patterns define the link. / Malkovets, V. G.; Griffin, W. L.; O'Reilly, S. Y.; Wood, B. J.

In: Geology, Vol. 35, No. 4, 04.2007, p. 339-342.

Research output: Contribution to journalArticle

Malkovets, VG, Griffin, WL, O'Reilly, SY & Wood, BJ 2007, 'Diamond, subcalcic garnet, and mantle metasomatism: Kimberlite sampling patterns define the link', Geology, vol. 35, no. 4, pp. 339-342. https://doi.org/10.1130/G23092A.1
Malkovets, V. G. ; Griffin, W. L. ; O'Reilly, S. Y. ; Wood, B. J. / Diamond, subcalcic garnet, and mantle metasomatism : Kimberlite sampling patterns define the link. In: Geology. 2007 ; Vol. 35, No. 4. pp. 339-342.
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