Home – Home – Jornals – Russian Geology and Geophysics 2015 number 11

Omphacite is a typomorphic mineral of eclogites, which is inappropriate to mineral assemblages of per-idotites. Nevertheless, findings of this mineral in inclusions in peridotitic diamonds can be considered as indi-rect evidence for the existence of this paradoxical mineral assemblage. In this paper we present experimental results on the interaction between carbonate-bearing amphibolite and olivine that model processes operated at the crust–mantle boundary in subduction zones. The experiments demonstrate growth of omphacite at the in-terface between acid melt and peridotite media at 2.9 GPa and 850–900 ºC; the omphacite coexists either with garnet and orthopyroxene or with phlogopite. The synthetic omphacite is exclusively of reactive-magmatic origin and does not form in metasomatic way. Findings of omphacite inclusions in peridotitic diamonds and in some pyroxenites from kimberlites are discussed in scope of the obtained experimental data.