Phlogopite from carbonatitic veins associated with the Poços de Caldas alkaline massif, SE Brazil: mineralogy and 40 Ar/ 39 Ar dating by the laser step heating method - Vlach, Silvio Roberto Farias; Vilalva, Frederico Castro Jobim; Ulbrich, Mabel N. C.; Ulbrich, H.; Vasconcelos, Paulo Marcos (South American Symposium on Isotope Geology, 2003)