Carbonatitic melts along the solidus of model lherzolite in the system CaO-MgO-Al2O3-SiO2-CO2 from 3 to 7 GPa

Article Abstract:

The solidus location of model lherzolite in the system CaO-MgO-Al2O3-SiO2-CO2 was experimentally determined from 3 to 7 GPa by finding the isobaric invariant points where liquid coexists with olivine, orthopyroxene, garnet and carbonate. Findings indicated that in a carbonate-bearing mantle, solidus and near-solidus melts will be CO2-rich and silica poor. The widespread proof for the presence of CO2 in both the oceanic and continental upper mantle indicates that such low degree SiO2-poor carbonatitic melts are common in the mantle, despite the rarity of carbonatites at the Earth's surface.

Carbonatites

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Phase equilibria in the silica-undersaturated part of the KAlSiO4 - Mg2SiO4 - Ca2SiO4 - SiO2 - F system at 1 atm and the larnite-normative trend of melt evolution

Article Abstract:

A study was conducted to analyze the effect of volatiles on the crystal fractionation path of ultramafic alkaline magmatic systems at moderate pressure. It also aimed to determine the link between the stability of liquid phlogopite and the development of larnite normative melilitite melts which may form from the late-stage residual melts by phlogopite, amphibole, clinopyroxene and Fe-Ti oxide fractionation. However, the results were limited in explaining the effect of H2O-F ratio on the crystallization of silicate melts.

Fractionation, Fractional distillation, Alkalic igneous rocks

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