Tourmaline-bearing quartzites at western contact of Kopan and Matkal gabbro complexes

A peculiar horizon of tourmaline-bearing quartzites has been identified in the study of basic intrusives of the South Urals. This horizon is quite consistent along the contacts of gabbro massifs, with the quartzites strongly metasomatized and altered in both structure and mineral composition. The tourmaline appears to be the result of an alkali metasomatism related to granitic intrusions. The principal sequence is albite, tourmaline and quartz. The quartzites appear to be of sedimentary origin, as they form a consistent horizon traceable for tens of kilometers and are intercalated with similarly consistent horizons of hornfels and schists. — F. E. Ingerson.