MANTLE SOURCES AND DIFFERENTIATION OF ALKALINE MAGMATIC SUITE OF LAGES, SANTA-CATARINA, BRAZIL

The alkaline-carbonatite district of Lages (Santa Catarina, Brazil) co ntains mafic-ultramafic and prevalent leucocratic bodies mainly compos ed of olivine melilitites, olivine nephelinites, basanites, phonotephr ites, nepheline syenites and peralkaline phonolites. Kimberlitic pipe breccias and carbonatitic rocks are also present. Petrography, mineral and bulk-rock chemistry and mass balance calculations show that diffe rentiated leucocratic rock-types can be derived by fractional crystall ization processes from basanitic magmas. Trace element and Sr-Nd isoto pic data suggest metasomatized mantle sources for the primary magmas a nd variable crystal contamination for the more differentiated rock-typ es.