stripes
Ankur consists of a central stock of quartz syenite and concentric rings of aegirine syenite and gabbro, the whole complex being 3 km in diameter. The gabbro of the outer ring contains labradorite, often highly altered, augite, usually uralitized to fibrous amphibole and biotite, with the latter minerals also present as primary phases; quartz is present close to the inner ring. The inner syenite ring contains large gabbro xenoliths and comprises microcline perthite, small crystals of albite-oligoclase, quartz and up to 20% aegirine plus arfvedsonite. The quartz syenite of the central stock consists of microcline perthite, oligoclase, quartz and occasional biotite. Chemical analyses are available in Jar-en-Nabi (1976) and palaeomagnetic data on three gabbro samples in Cavanagh (1979).
CAVANAGH, B.J. 1979. Rb-Sr geochronology of some pre-Nubian igneous complexes of central and northeastern Sudan. Ph.D. Thesis, University of Leeds. 239 pp. (unpublished)GASS, I.G. 1955. The geology of the Dunganab area, Anglo-Egyptian Sudan. M.Sc. thesis, University of Leeds. 100 pp. (unpublished)JAR-EN-NABI, M.E. 1976. The geology of some ring complexes from the Red Sea Hills (N.E. Sudan). Ph.D. thesis, Portsmouth Polytechnic. 151 pp. (unpublished)