Abstract
Phlogopites from the carbonatites intruded into the Jacupiranga alkalic complex have FeO/(FeO + MgO) within the restricted range 0.06 to 0.12, and BaO varying from 0.1 up to 10.3 wt.%. Zoning with respect to BaO may be small, or it may exceed 3–4% BaO. Phlogopites and biotites from other carbonatites contain much less BaO, commonly below 0.7%, but values of FeO/(FeO + MgO) range up to 0.66. Phlogopites from mantle peridotite nodules and kimberlites have BaO contents less than 0.7%, with FeO/(FeO + MgO) varying from low values for mantle phlogopites (corresponding to those of the Jacupiranga carbonatites) up to values of at least 0.7 for kimberlite phlogopites. Leucite-bearing lavas contain high Ba micas with FeO/(FeO + MgO) from 0.09–0.6, and BaO up to 7.3%.
