Kila-Warji (Kila-Wurji)

About 26 km long and covering 240 km2 this complex comprises two centres, Kila in the north and the rather larger Warji centre to the south. Kila rises to a high central hill whereas Warji forms low hills rarely rising to more than 60 m. Kila is composed mainly of ring-dykes and stocks but Warji consists essentially of volcanic rocks that have been intruded and domed by syenites and granites. The complex contains the most extensive area of syenites and trachytes in the whole alkaline province. The development of the centre involved a rather elaborate sequence of intrusion, extrusion and structural events which are detailed by Turner (1968) and summarised by Bennett et al. (1984). Initial activity was focussed on the Warji centre and commenced with extrusion of voluminous rhyolitic ignimbrites, some agglomerates and minor trachytes, which in the east are estimated to be 450-600 m thick. These were followed by feldsparphyric trachytes that are thought to fill a caldera and both are intruded by syenite that is compositionally similar to the trachytes. The syenite contains phenocrysts of alkali feldspar and labradorite-andesine with, in one area, poikilitic olivine and ferroaugite rimmed by hornblende and ferrorichterite, while the rims elsewhere are of biotite and ferrorichterite-arfvedsonite. Two 0.5-0.6 km diameter trachyte plugs cut the syenite in the southwest and there is also a dyke of porphyry with phenocrysts including fayalite and ferrohedenbergite and a small intrusion of porphyritic granite. There are also two large intrusions of arfvedsonite granite in which the amphibole is poikilitic and aegirine and astrophyllite are accessory. The Kila centre consists of four overlapping intrusions that Bennett et al. (1984) call ring structures, although from the maps this is far from clear, earlier intrusions being mostly destroyed by the later ones. The remnants of Centre 1 are porphyritic trachyte and peralkaline granites including a porphyritic variety containing varying proportions of aegirine or amphibole and an aegirine granite with a little arfvedsonite. The second centre consists of a syenite while the third, which occupies two thirds of the complex, is mainly a quartz syenite porphyry ring intrusion around a body of quartz porphyry. The fourth centre consists principally of aegirine granite which was emplaced between Centres 2 and 3. The rock consists of quartz, perthite, aegirine, a little arfvedsonite, aenigmatite, astrophyllite, zircon and fluorite.