Salala (Sofaya)

This occurrence is formed of two overlapping ring complexes about 50% of the larger northern one being hidden beneath recent alluvium. The highly variable country rocks include andesitic lavas and tuffs, diorite and other intrusive rocks, and a range of sediments. The central areas of both halves are occupied by basic non-alkaline rocks. The 500-600 m wide, discontinuous part of the southern ring is a quartz-riebeckite syenite consisting of about 80% microcline, perthite, rare discrete sodic plagioclase, biotite and riebeckite/arfvedsonite with occasional aegirine inclusions. The central part of the southern ring is occupied by a meladiorite while to the north of the centre is a leucocratic syenite of orthoclase, a little perthite and albite. The northern ring intrusion consists of a riebeckite-aegirine syenite which forms an almost complete outer ring within which are irregular areas of pyroxene syenite, nepheline syenite, troctolite and a volcanic breccia. The rock of the outer ring comprises about 60% perthite, some oligoclase, hornblende, riebeckite, which sometimes rims hornblende, aegirine and biotite, the mafic minerals being very irregular in their distribution. The pyroxene syenite is essentially a perthite - aegirine-augite rock with some alteration of the pyroxene to amphibole and biotite. The nepheline syenite carries xenoliths of the pyroxene syenite and meladiorite and consists of perthite, nepheline, aegirine, arfvedsonite and biotite. A small area of troctolite which is present in the northern ring contains intermediate plagioclase, olivine and accessories. There are numerous dykes the majority being of various types of microsyenite with some dolerites. A range of chemical analyses, including some trace elements, are given by Jar-en-Nabi (1976) and palaeomagnetic data by Cavanagh (1979).