A primary natrocarbonatitic association in the Deep Earth

Abstract

In addition to ultramafic and mafic associations, a primary natrocarbonatitic association occurs in the lower mantle. To date, it was identified as inclusions in diamonds from the Juina area, Mato Grosso State, Brazil. It comprises almost 50 mineral species: carbonates, halides, fluorides, phosphates, sulfates, oxides, silicates, sulfides and native elements. In addition, volatiles are present in this association. Among oxides, coexisting periclase and wüstite were identified, pointing to the formation of the natrocarbonatitic association at a depth greater than 2,000 km. Some ironrich (Mg,Fe)O inclusions in diamond are attributed to the lowermost mantle. The initial lower-mantle carbonatitic melt formed as a result of low-fraction partial melting of carbon-containing lower-mantle material, rich in P, F, Cl and other volatile elements, at the core-mantle boundary. During ascent to the surface, the initial carbonatitic melt dissociated into two immiscible parts, a carbonate-silicate and a chloride-carbonate melt. The latter melt is parental to the natrocarbonatitic lower-mantle association. Diamonds with carbonatitic inclusions were formed in carbonatitic melts or high-density fluids.

Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition

“…Previously, a mineral with the probable composition of KMgF 3 had been reported in sublimates from Nyiragongo volcano (Democratic Republic of Congo) by Herman et al (1960), although this was not recognised as a novel mineral species. Parascandolaite, has also been found as nano-inclusions in diamonds from Juina by Kaminsky et al (2016).…”

“…Although Al-fluorides had been recognized in fumaroles from the Hekla (Oskarsson, 1981) and Mount Erebus (Rosenberg, 1988) volcanoes, a complete structural characterization was not available until material from fumaroles of the Eldfell volcano (Iceland) was undertaken by Jacobsen et al (2014). A mineral with the composition of oskarssonite, together with parascandolaite, has also been found as nano-inclusions in diamonds from Juina by Kaminsky et al (2016). Oskarssonite [Al(F 2.62 (OH) 0.49 )] adopts the rhombohedral space group R 3c (#167) in common with the synthetic analogue α-AlF 3 (Le Bail and Calvayrac, 2006).…”

Isotopic fractionation of oxygen and carbon in decomposed lower-mantle inclusions in diamond

“…Both studied mineral assemblages in these diamonds belong to the natrocarbonatite association, in which nyerereite (Na,K) 2 Ca(CO 3 ) 2 forms the matrix of the inclusion (Kaminsky et al 2009(Kaminsky et al , 2015.…”

The inclusions of SiO2 in sublithospheric diamonds

“…Подобное взаимодействие может привести к формированию при давлениях 10-16 гПа новых минеральных ассоциаций, которые должны быть промежуточными между метаперидотитами и метабазитами (Thomson et al, 2016). В качестве источника карбонатных расплавов в мантии рассматривают как перидотитотовые субстраты (Kaminsky et al, 2016;Рябчиков, когарко, 2016), так и субдуцированные породы океанической литосферы (Walter et al, 2008). характеристики изотопного состава кислорода включений силикатов (в т.ч.…”