Towards composition of carbonatite melts in peridotitic mantle

Shatskiy, Anton; Bekhtenova, Altyna; Podborodnikov, Ivan V.; Arefiev, Anton V.; Litasov, Konstantin D.

doi:10.1016/j.epsl.2022.117395

Cited by 8 publications

(1 citation statement)

References 46 publications

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“…These had high proportions of melt to circumvent the difficulty of finding the products of the reaction: carbonate-rich melts have low viscosity and are highly mobile at low melt fractions, so evidence of reaction with the peridotite may be challenging to observe. These experiments confirm the observation from earlier studies [20][21][22][23] , that carbonatitic melt consumes orthopyroxene in the peridotite and may crystallize garnet 20 , clinopyroxene 21 , and magnesite 20 . Only small chemical changes are observable in the harzburgite wall rock: alkalies do not form new, distinct phases, but are carried further in the carbonatitic melt 20,21 .…”

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confidence: 90%

Diamonds, dunites, and metasomatic rocks formed by melt/rock reaction in craton roots

Pintér

Foley

Yaxley

2022

Commun Earth Environ

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The thick mantle lithosphere beneath cratons consists of strongly reduced rocks that have reacted with oxidized melts. These low-silica, incipient melts are rich in CO2 and H2O and react with surrounding rocks forming an enriched zone at the base of the lithosphere, which is the source region for many diamonds. Here, we reproduce these reactions in novel experiments in which oxidised, hydrous carbonate-rich melts are reacted with reduced, depleted peridotite at 5 GPa pressure. Results explain several key features of the mantle sample in kimberlites as products of a single process, namely the formation of diamonds, phlogopite and alkali-amphibole bearing rocks, iron-rich dunites, and garnets and clinopyroxenes with pyroxenitic compositions. Initially, redox freezing occurs where melts meet the reduced peridotite, depositing diamonds and associated garnet and clinopyroxenes. The spreading reaction front leaves behind Fe-rich dunite, and crystallizing phlogopite and amphibole when the melt solidifies at the reaction front.

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