Graphite and diamond formation via the interaction of iron carbide and Fe,Ni-sulfide under mantle P-T parameters

摘要

Experimental research in the Fe3C-(Fe,Ni)S system was carried out. The objective of the investigation was to model the reactions of carbide-sulfide interaction related to graphite (diamond) formation in reduced lithosphere mantle domains. T ae 1200A degrees C is the formation temperature of the Ni-cohenite + graphite assemblage coexisting with two immiscible melts such as sulfide (Fe-60-Ni-3-S-37)(L) and metal-sulfide (Fe-71-Ni-7-S-21-C-1)(L) containing dissolved carbon. D cent ae 1300A degrees C is the generation temperature of a unified melt such as (Fe-80-Ni-6-S-10-C-4)(L) characterized by graphite crystallization and diamond growth. The extraction of carbide carbon during the interaction with the sulfide melt can be considered as one of the potential mechanisms of graphite and diamond formation in the reduced mantle.