Lower mantle multicomponent systems in physico-chemical experiments

Abstract

Ferropericlase, bridgmanite, Ca-perovskite, magnesiowustite and stishovite have been justified as the major rock-forming lower mantle minerals. This deduction is in excellent agreement with diamond-hosted inclusions and experimental subsolidus phases of pyrolite. The minerals belong to ultrabasic-basic lower mantle system MgO-FeO-CaO-SiO2. Experimental study of melting relations on the boundary MgO-FeO-SiO2 join of the system has revealed a peritectic reaction of bridgmanite and melt with formation of SiO2 (stishovite) and MgO-FeO solid solution oxides after bridgmanite breakdown (effect of stishovite paradox). The invariant peritectic point forms the basis for the liquidus structure of most representative lower mantle system MgO-FeO-SiO2-CaSiO3 being studied in physico-chemical experiments at 24 GPa. The peritectic reaction of bridgmanite opens the door to ultrabasic-basic evolution of lower mantle magmatism.