Lower mantle diamonds from Rio Soriso (Juina area, Mato Grosso, Brazil)

Patrick C. Hayman, Maya G. Kopylova*, Felix V. Kaminsky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Citations (Scopus)

Abstract

The morphology, colour, fluorescence, cathodoluminescence, nitrogen content and aggregation state, internal structure and mineral inclusions have been studied for 69 alluvial diamonds from the Rio Soriso (Juina area, Mato Grosso State, Brazil). Nitrogen in most diamonds (53%) is fully aggregated as B centres, but there is also a large proportion of N-free stones (38%). A strong positive correlation between nitrogen and IR-active hydrogen concentrations is observed. The diamonds contain (in order of decreasing abundance) ferropericlase, CaSi-perovskite, magnetite, MgSi-perovskite, pyrrhotite, 'olivine', SiO2, perovskite, tetragonal almandine-pyrope phase and some other minerals represented by single grains. The Rio Soriso diamond suite is subdivided into several subpopulations that originated in upper and lower mantle of ultramafic and mafic compositions, with the largest subgroup forming in the ultramafic lower mantle. Analysed ferropericlase grains are enriched in Fe (Mg#=0.43-0.89), which is ascribed to their origin in the lowermost mantle. The Juina kimberlites may be unique in sampling the material from depths below 1,700 km that ascended in a plume formed at the core-mantle boundary.

Original languageEnglish
Pages (from-to)430-445
Number of pages16
JournalContributions to Mineralogy and Petrology
Volume149
Issue number4
DOIs
Publication statusPublished - Jun 2005
Externally publishedYes

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