The Alkaline Centre of Yelele and its Bearing on the Petrogenesis of other Eastern Uganda Volcanoes

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Abstract
An account is given of Yelele, a Miocene volcano, situated on the Turkana escarpment, north-east Uganda. It is composed of lavas and dykes of nephelinite, phonolite, tephrite, and trachyte together with olivine-bearing varieties, and has a central plug of ijolite and nepheline syenite.The lavas are described and compared with those of other eastern Uganda centres and the petrogenesis discussed in the light of experimental data from the Geophysical Laboratory of the Carnegie Institution of Washington.A northern (Yelele) plagioclase-bearing suite of lavas and a southern (Elgon) melilite-bearing suite are derived by different fractionation trends from an olivine melanephelinite parent which itself is the dense portion of a nephelinitic parent magma.