Chimbiri Hills

These are a group of small hills in the plain north-northwest of the Namangali Vent (No. 103-00-039), to which they may be related. They consist of basement gneisses cut by dykes of dolerite, microfoyaite, phonolite and solvsbergite. Three small vents, on the Salambidwa, Mikomwa and Chipalanje Hills, are filled with agglomerate consisting of fragments of country rock and trachyte in a matrix of alkali feldspar laths and abundant carbonate. In two of the occurrences alkali feldspar locally forms spherulitic structures.