A microinclusion of lower-mantle rock and other minerals and nitrogen lower-mantle inclusions in a diamond

Felix V. Kaminsky*, Richard Wirth, Anja Schreiber

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

A microcrystalline polymineral aggregate was identified as an inclusion in a diamond from the Rio Soriso area, Mato Grosso State, Brazil. It is composed of iron carbides, Fe-rich periclase (with exsolved magnesioferrite), and two orthorhom-bic, postspinel phases-Mg-Cr-Fe and Ca-Cr oxides, which are new mineral phases. This association was formed during several stages and may be considered as a rock microfragment from the lower mantle. In addition to the carbide-oxide fragment, other phases were identified as inclusions in the diamond, such as parascandolaite KMgF3 (that is stable at pressures of up to 50 GPa) in association with orthorhombic MgO, and porous dolomite occurring together with nanoinclusions of calcite, apatite, spinel, Fe-sulfide, and an assemblage of periclase plus wüstite. These minerals belong to the carbonatitic association and, along with syngenetic nanoinclusions of fluid nitrogen, represent the media of diamond formation. The assemblage of peri-clase and wüstite within the carbonatitic matrix points to the origin of diamond from a carbonatitic environment within the lower mantle under pressure conditions of ≥85-86 GPa (∼1,900 km depth).

Original languageEnglish
Pages (from-to)83-104
Number of pages22
JournalCanadian Mineralogist
Volume53
Issue number1
DOIs
Publication statusPublished - 1 Jan 2015
Externally publishedYes

Keywords

  • CaCr O
  • MgCr O
  • Iron carbide
  • Lower mantle
  • Fe SiC
  • Nitrogen
  • Parascandolaite
  • Wüstite

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