Mantle sources and differentiation of alkaline magmatic suite of Lages, Santa Catarina, Brazil

Abstract

The alkaline-carbonatite district of Lages (Santa Catarina, Brazil), contains mafic-ultramafic and prevalent leucocratic bodies mainly composed of olivine melilitites, olivine nephelinites, basanites, phonotephrites, 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 differentiated leucocratic rock-types can be derived by fractional crystallization processes from basanitic magmas. Trace element and Sr-Nd isotopic data suggest metasomatized mantle sources for the primary magmas and variable crustal contamination for the more differentiated rock-types.