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Geology and geochemistry of the Ol Doinyo Nyokie trachyte ignimbrite vent complex, south Kenya rift valley

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Abstract

The Ol Doinyo Nyokie complex is of late Pleistocene age and occurs in the floor of the south Kenya rift valley. It consists of a shallow depression 5 km long and 3 km wide occupied by ash-flows, surrounded by a zone of trachyte dykes, and with a dome-shaped ignimbrite vent at its eastern end. The complex began to form approximately 0.7 m.y. ago with eruption of ash-flows from fissures accompanied by subsidence, followed by emplacement of dykes in the fissures and the growth of a steep-sided ignimbrite tuff-ring. The rocks are all of quartz trachyte compositions similar to those of the flood lavas upon which the complex is built. Detailed geochemical evidence indicates that the ignimbrite magma was derived from the flood lava magma by alkali feldspar fractionation.

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  1. Center for Volcanology, University of Oregon, Eugene, Oregon, U.S.A.

    B. H. Baker

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Baker, B.H. Geology and geochemistry of the Ol Doinyo Nyokie trachyte ignimbrite vent complex, south Kenya rift valley. Bull Volcanol 39, 420–440 (1975). https://doi.org/10.1007/BF02597265

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  • DOI: https://doi.org/10.1007/BF02597265

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