Daura

The form of this complex is not clear, consisting as it does of outcrops of granite, syenite and rhyolite scattered over an area of 25x10 km. Rhyolite is the most abundant rock type and includes lavas, tuffs, agglomerates and, locally, ignimbrites as well as numerous intrusions. The extrusive rhyolites, which are considered by Turner and Webb (1974) to have emanated from many pipes and fissures, are sparsely feldsparphyric and the ignimbrites are comenditic. The intrusive rhyolites form dykes and broad dyke-like intrusions and contain phenocrysts of quartz, alkali feldspar and hedenbergitic pyroxene with arfvedsonite, aegirine-augite and aenigmatite in the groundmass. A quartz syenite intrusion of about 1 km2 in the central part of the area has chilled margins inside which is a zone of fine- to medium-grained quartz-rich, peralkaline syenite containing sodic amphibole, aegirine-augite and aenigmatite. This grades into a coarse-grained, quartz-poor hornblende syenite which forms the central part of the intrusion. Biotite granite occupies an isolated hill to the southeast. It is of variable granularity and includes varieties with fluorite and accessory columbite and zircon.