The experiments demonstrate that kamafugite and alkali-rich carbonatite melts are immiscible at 1.7 GPa, 1220 ¡ãC. Trace element partition coefficients obtained from static- and centrifuging piston cylinder experiments are within factor 5 from unity and deviate less than a factor of 2 from unity for 26 out of 37 trace elements investigated. The alkali- and earth alkali-elements have Di ¡Ý 1, indicating that carbonatite melts in equilibrium with alkaline silicate melts should be at least as alkali-rich as the silicate melts. HFSE partition preferentially into the silicate melt.
A comparison of the experimental partition coefficients with natural carbonatite-kamafugite pairs from the Intra Apennine Province reveals good agreement (except for the alkalis), supporting that liquid immiscibility could indeed explain the observed rock suites. Original carbonatite compositions are not well preserved due to secondary leaching that almost completely removed the alkalis leading to significant uncertainties and compositional variations and potentially modified trace element concentrations too. Based on the observed trace element concentrations, large volume assimilation of sedimentary calcite is unlikely. We thus propose that CO2 was already present in the parental primitive magmas forming the kamafugites. The carbonatites formed by unmixing from the silicate magmas and the related CO2-saturation were most probably responsible and triggered the explosive eruptions in the Intra Apennine Province.