Evidence for evolution of growth media in superdeep diamonds from Sao-Luis (Brasil)

D. A. Zedgenizov, A. L. Ragozin, V. S. Shatsky, H. Kagi, S. Odake, W. L. Griffin, D. Araujo, O. P. Yuryeva

    Research output: Contribution to journalMeeting abstract

    Abstract

    Diamonds from Sao-Luis (Brazil) are known to be originated from the depths of transition zone and lower mantle [1]. In this study we consider some aspects of the composition and evolution of growth media for diamonds from this locality. CL imaging has revealed the complex growth history for most diamonds, reflecting their formation in several stages. Nitrogen content in an individual diamonds varies from several to 500 ppm. An apparent tendency for the 3107 cm (super -) (super 1) peak intensity to increase with increasing the nitrogen content gives support to the idea that the conditions favouring the incorporation of nitrogen in these diamonds might also favour the incorporation of hydrogen. Specific feature of diamonds from Sao-Luis is extremely high nitrogen aggregation state (90-100 ±). The set of luminescence centers N3, H3, H4, 490.7 is typical for all diamonds. Radiation-induced centers with peaks at 536 and 576 nm are often observed. The total range of carbon isotope composition in diamonds studied by SIMS makes up from -3.3 to -20.3 ppm of d (super 13) C. Some diamonds show local variations of d (super 13) C between different growth zones (up to 7 ppm). The dominant inclusions in studied diamonds are CaSi-perovskite and AlSi-phases. MgSi- and CaTi-perovskites, ferropericlase, native iron, coesite and zircon have also been found. Raman shift of coesite peak show high residual pressure (>3 GPa at ambient temperature). FTIR study of some microinclusion-bearing diamonds showed that water and carbonates are not major components of diamond-forming fluids. LA-ICPMS bulk composition has significant enrichment in Ca, Fe and Al and strong depletion in Mg. Trace elements show general enrichment in Ti and V and depletion in Sr, LREE and Ni. Most probable source for such environments might be fluids from deeply subducted rocks of metasomatized oceanic lithosphere.
    Original languageEnglish
    Pages (from-to)2244
    Number of pages1
    JournalMineralogical Magazine
    Volume75
    Issue number3
    Publication statusPublished - 2011
    EventGoldschmidt Conference (21st : 2011) - Prague, Czech Republic
    Duration: 14 Aug 201119 Aug 2011

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