Carbonatitic Melts and Their Role in Diamond Formation in the Deep Earth

Carbonatitic high-density fluids and carbonate mineral inclusions in lithospheric and sub-lithospheric diamonds reveal comparable compositions to crustal carbonatites and, thus, support the presence of carbon-atitic melts to depths of at least the mantle transition zone (similar to 410-660 km depth). Diamonds and high pressure-high temperature (HP-HT) experiments confirm the stability of lower mantle carbonates. Experiments also show that carbonate melts have extremely low viscosity in the upper mantle. Hence, carbonatitic melts may participate in the deep (mantle) carbon cycle and be highly effective metasomatic agents. Deep carbon in the upper mantle can be mobilized by metasomatic carbonatitic melts, which may have become increasingly volumetrically significant since the onset of carbonate subduction (similar to 3 Ga) to the present day.

Automated summary

Carbonatitic high-density fluids and carbonate mineral inclusions found in diamonds suggest the presence of carbonatitic melts in the crust and deep mantle. High pressure-high temperature experiments and diamond studies indicate the stability and behavior of carbonate melts in different regions of the Earth's mantle, playing a key role in the deep carbon cycle and metasomatism.