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Tholeiite from the Simien alkali basalt centre, Ethiopia

Published online by Cambridge University Press:  01 May 2009

M. J. LeBas  and
P. A. Mohr
M. J. LeBas
Affiliation:
Department of Geology, University of Leicester, Leicester LE1 7RH, England
P. A. Mohr
Affiliation:
Smithsonian Inst. AstroPhysical Observatory, 60 Garden Street, Cambridge, Mass. 02138, U.S.A.
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Summary

The Ethiopian Cainozoic volcanics associated with the African rift system comprise one of the world's most voluminous alkaline igneous provinces. The Simien Mountains are the remnants of a Miocene alkali olivine-basalt volcanic centre in the north-western part of this province. The end-phase activity at Simien featured intrusion of dyke-swarms of two trends, one parallel to the rift system, the other almost perpendicular to it. Dykes of the rift trend are typically alkaline, but a dyke sampled from the other trend proves to be an olivine-tholeiite. Its presence is interpreted, along with similar rocks from the Harar region in eastern Ethiopia, in terms of upper mantle rifting extending from the Gulf of Aden and Red Sea under the continental blocks of the Ethiopian swell.

Type
Articles
Information
Geological Magazine , Volume 107 , Issue 6 , November 1970 , pp. 523 - 529
Copyright
Copyright © Cambridge University Press 1970

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References

REFERENCES

Comucci, P. 1933. Rocce dello lemen raccolte della missione di S. E. Gasperi. Periodico Miner., 4, 86–131.Google Scholar
Comucci, P. 1950. Le vulcaniti del lago Tana (Africa Orientale). Acad. Naz. Lincei Roma.Google Scholar
Cox, K.G., Gass, I.G. & Mallick, D.I.J. 1969. The evolution of the volcanoes of Aden and Little Aden, South Arabia. Q. Jl geol. Soc. Lond., 124, 283–308.CrossRefGoogle Scholar
Davies, K.A. 1953. A basalt flow and feeding dyke N.E. Uganda. Geol. Mag. 90, 268–273.CrossRefGoogle Scholar
Gass, I.G. & Gibson, I.L. 1969. Structural evolution of the rift zones in the Middle East. Nature, Lond. 211, 926–930.CrossRefGoogle Scholar
Girdler, R.W. 1970. An aeromagnetic survey of the junction of the Red Sea, Gulf of Aden and Ethiopian rifts. Phil. Trans. R. Soc., A, 267, 359–368.Google Scholar
Gortani, M. & Bianchi, A. 1937. Osservazioni geologiche e petrografiche nella regione di Harar (Africa orientale italiana). Boll. Soc. geol. ital., 56, 499–516.Google Scholar
Harris, P.G. 1969. Basalt type and African Rift valley tectonism. Tectonophysics, 8, 427–436.CrossRefGoogle Scholar
Hieke-Merlin, O. 1950. I basalti dell'Africa Orientale. Mem. Ist. Geol. Min. Univ. Padova, 17, 1–18.Google Scholar
Le Bas, M.J. & Mohr, P.A. 1968. Feldspathoidal rocks from the Cainozoic volcanic province of Ethiopia. Geol. Rdsch., 58, 273–280.CrossRefGoogle Scholar
Mohr, P.A. 1967. Review of the geology of the Simien mountains. Bull. Geophys. Obs. Addis Ababa, 10, 79–93.Google Scholar
Mohr, P.A. & Rogers, A.S. 1966. Gravity traverses in Ethiopia. Bull. Geophys. Obs. Addis Ababa, 9, 7–58.Google Scholar
Youssef, M.I. 1968. Structural pattern of Egypt and its interpretation. Bull. Am. Ass. Petrol. Geol., 52, 601–614.Google Scholar