Experimental evidence on the origin of Ca-rich carbonated melts formed by interaction between sedimentary limestones and mantle-derived ultrabasic magmas

Abstract In this experimental study, we documented the formation of strongly ultrabasic and ultracalcic melts through interaction melilititic basanitic with calcite. Three to moderately SiO2-undersaturated volcanic rocks from Bohemian Massif (central Europe) were mixed 10, 30, 50 wt% CaCO3 melted at 1100, 1200, 1300 °C 2 kbar evaluate maximum amount carbonate that can be assimilated by natural shallow depths. Experiments revealed a surprisingly complete dissolution CaCO3, only rarely reaching saturation, typical liquidus phases represented olivine, spinel, melilite, clinopyroxene. Only in runs most compositions did abundant monticellite form instead For all starting mixtures, (SiO2 down 15.6 wt%), lime-rich (CaO up 43.6 (CaO/Al2O3 ~27) melt produced 1200 °C, ~25 dissolved CO2. When present, quenched olivine showed much higher forsterite content (Fo95–97) than samples (Fo79–85). The two major results study are (1) silicate-carbonatite do not necessarily imply existence carbonatitic components mantle, because they also during limestone assimilation, (2) Fo-rich olivines cannot used infer any primitive character nor high potential temperature (Tp).