Diamond From the Los Coquitos Area, Bolivar State, Venezuela

Kaminsky, Felix V.; Zakharchenko, Olga D.; Khachatryan, Galina K.; Griffin, William L.; Channer, Dominic M. DeR.

doi:10.2113/gscanmin.44.2.323

Cited by 9 publications

(2 citation statements)

References 22 publications

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“…It has an FeO content of 97 wt.%, with only 0.09 wt.% MgO, and Mg# = 0.2. It has been suggested that this wüstite might belong to the lowermost mantle (Kaminsky et al, 2006). The present study has identified other wüstite inclusions in diamond from the Juina area, Brazil.…”

Section: Carbonatitic Mineral Association In Diamondsupporting

confidence: 49%

Nyerereite and nahcolite inclusions in diamond: evidence for lower-mantle carbonatitic magmas

et al. 2009

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Nyerereite and nahcolite have been identified as micro- and nano-inclusions in diamond from the Juina area, Brazil. Alongside them are Sr- and Ba-bearing calcite minerals from the periclase-wiistite series, wollastonite II (high), Ca-rich garnet, spinels, olivine, phlogopite and apatite. Minerals of the periclase- wustite series belong to two separate groups: wustite and Mg-wustite with Mg# = 1.9—15.3, and Fe- periclase and periclase with Mg# = 84.9—92.1. Wollastonite-II (high, with Ca:Si = 0.992) has a triclinic structure. Two types of spinel were distinguished among mineral inclusions in diamond: zoned magnesioferrite (with Mg# varying from 13.5—90.8, core to rim) and Fe spinel (magnetite). Olivine (Mg# = 93.6), intergrown with nyerereite, forms an elongate, lath-shaped crystal and most likely represents a retrograde transformation of ringwoodite or wadsleyite. All inclusions are composed of poly-mineralic solid mineral phases. Together with previously found halides, sulphates and other mineral inclusions in diamond from Juina, they form a carbonatitic-type mineral paragenesis in diamond which may have originated in the lower mantle and/or transition zone. Wustite inclusions with Mg# = 1.9—3.4, according to experimental data, may have formed in the lowermost mantle. The source for the observed carbonatitic-type mineral association in diamond is lower-mantle natrocarbonatitic magma. This magma may represent a juvenile mantle melt, or be the result of low-degree partial melting of deeply-subducted carbonated oceanic crust. This magma was rich in volatiles, such as Cl, F and H, which played an important role in the formation of diamond.

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Section: Carbonatitic Mineral Association In Diamondsupporting

confidence: 49%

Nyerereite and nahcolite inclusions in diamond: evidence for lower-mantle carbonatitic magmas

et al. 2009

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“…Compositional features and associations of some grains of ferropericlase gave reasons to suggest their origin within the D" layer at the core -mantle boundary (Harte et al, 1999;Kaminsky et al, 2006). Recently one of diamond crystals from the Juina area in Brazil was found to contain carbonate and halide inclusions associated with wüstite + periclase association, presumably from the D" layer (Kaminsky et al, 2009a).…”

Section: Introductionmentioning

confidence: 99%

Iron Carbide Inclusions in Lower-Mantle Diamond From Juina, Brazil

Kaminsky

Wirth

2011

The Canadian Mineralogist

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121

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Iron carbides in association with native iron, graphite, and magnetite were identified in a diamond from the Juina area, Brazil, which contains a series of other, lower-mantle mineral inclusions. Among iron carbides, Fe 3 C, Fe 2 C ("chalypite"), and Fe 23 C 6 (haxonite) are present; the two latter are identified in the terrestrial environment for the first time. Some of the analyzed iron carbide grains contain 7.3-9.1 at.% N and are, in fact, nitrocarbide. It is suggested, based on the high-pressure mineral paragenesis previously observed in the diamond and experimental data on the system Fe-C, that "chalypite" crystallized, within a pressure interval of 50-130 GPa, from an iron-carbon melt, rich in nitrogen. Following crystallization, iron carbides and native iron were partially oxidised to magnetite, and encapsulated in diamond along with other highpressure minerals. The finds of various iron carbides, some of which are rich in nitrogen, in lower-mantle diamond confirm a significant role of carbides and nitrogen in the Earth's interior.

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