The alkaline district of Fortaleza (Cearä, Brazil) consists of a number of phonotephritic plugs, domes, and dykes cropping out in the Precambrian basement, aged around 30 Ma.Chemically and petrographically the rocks range in composition from tephrites and phonolitic tephrites to peralkaline phonolites. At one locality (Caruru), olivine clinopyroxenite, essexite, and nepheline syenite xenoliths of cognate origin...