The role of garnetization of olivine in olivine-diopside-jadeite system in the ultramafic-mafic evolution of the upper-mantle magmatism (experiment at 6 GPa).

Peritectic mechanisms, controlling fractional ultrabasic-basic evolution of the upper mantle magmatism and genesis of the peridotitepyroxeniteeclogite rock series, are substantiated in theory and experiment. Melting phase relations of a differentiated mantle material are studied with polythhermal section method in the multicomponent olivineclinopyroxene/omphacitecorundumcoesite system with boundary compositions duplicated these of peridotitic and eclogitic minerals. The peritectic reaction of orthopyroxene and melt with formation of clinopyroxene (the opthopyroxene clinopyroxenization reaction) has been determined at a liquidus surface of the ultrabasic olivineorthopyroxeneclinopyroxenegarnet system. As a result of the reaction the temperature-regressive univariant curve olivine + clinopyroxene + garnet + melt is formed. A further evolution of magmatism has experimentally studied at 6 GPa in the ultrabasic-basic olivinediopsidejadeitegarnet system with changeable compositions of the diopsidejadeite solid solutions (controlling the clinopyroxene omphacite mineralogy). Peritectic reaction of olivine and melt with formation of garnet was established on the liquidus surface of the ternary olivinediopsidejadeite system as the mechanism of olivine garnetization and going to the univariant curve omphacitegarnetmelt with formation of bimineral eclogites. Structure of the liquidus surface for the olivinediopsidejadeitegarnet system is inferred, and its role as a physic-chemical bridge between ultrabasic olivinebearing peridotitepyroxenitic and basic silica-saturated eclogitic compositions of the garnetperidotite facies matter. The new experimental physic-chemical results reveal the genetic links between ultrabasic and basic rocks as well as mechanisms of the uninterrupted fractional magmatic evolution and petrogenesis from the olivinebearing peridotitepyroxenitic to silica-saturated eclogite-grospyditicrocks. This provides an explanation for the uninterrupted composition trends for rock-forming components in clinopyroxenes and garnets of the differentiated rocks of the garnetperidotite facieis.