Immiscibility of Sulfide-Silicate Melts in the Mantle: Role in the Syngenesis of Diamond and Inclusions (Based on Experiments at 7.0 GPa)

摘要

Sulfides of Fe, Ni, and Cu are the most abundant accessory minerals of mantle peridotites, pyroxenites, and eclogites, including their diamond-bearing varieties. These sulfides are found as contact coatings and often as syngenetic solid inclusions in close association with diamonds from kimberlites. Multiphase diamond-sulfide-phlogopite intergrowths are known as inclusions in garnets from the garnet-cli-nopyroxene-quartz rock of the Kokchetav Massif. This testifies to the occurrence of sulfide phases in the parental material during the nucleation and growth of diamond. Sulfides have also been found in the immediate parental carbonate-silicate material represented by the fluid-bearing multiphase inclusions in diamonds from kimberlites. Inclusions of this type also contain silicates, carbonates, phosphates, carbon dioxide, and water as fluid components that are stable at room temperature and 1.5-2.1 GPa. The material of these inclusions was likely captured as carbonatite melts by growing diamonds. After cooling, the inclusions were either transformed into an assemblage of solid and "fluid" phases or quenched as carbonatitic glasses with accompanying minerals.