Portal de Periódicos da CAPES

Ethiopian rift and plateaus: Some volcanic petrochemical differences

1971; American Geophysical Union; Volume: 76; Issue: 8 Linguagem: Inglês

10.1029/jb076i008p01967

2156-2202

P. A. Mohr,

Geology and Paleoclimatology Research

Journal of Geophysical Research (1896-1977)Volume 76, Issue 8 p. 1967-1984 Ethiopian rift and plateaus: Some volcanic petrochemical differences P. A. Mohr, P. A. MohrSearch for more papers by this author P. A. Mohr, P. A. MohrSearch for more papers by this author First published: 10 March 1971 https://doi.org/10.1029/JB076i008p01967Citations: 55AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Volcanism on the Arabo-Ethiopian swell has accompanied the development of the three traversing spreading zones conjoining at Afar: the Red Sea, Gulf of Aden, and African rift systems. The Red Sea and Gulf of Aden floors are formed by oceanic tholeiites, but Afar and the main Ethiopian rift show a wider range of more alkaline volcanics. related to slower crustal spreading rates. The high plateaus between the rifts have had a strongly alkaline volcanism. The plateau basalts and especially the intermediate lavas are much more undersaturated than their rift equivalents, and are enriched in potash and Al/Fe. The silicic volcanics of the rift are soda-iron enriched relative to the plateau silicics. Magmatic composition can be equated with depth of melting, but the voluminous silicic volcanics are not the products of fractionation, direct partial melting, or anatexis of continental crust: the accretion hypothesis of Battey is supported and developed. References Augustithis, S. S., On the origin of olivine and pyroxene nodules in basalts, Chemie der Erde, 24, 197–210, 1965. Aumento, F., Magmatic evolution on the mid-Atlantic ridge, Earth Planet. Sci. Lett., 2, 225–230, 1967. Aumento, F., The mid-Atlantic ridge near 45°N. II. Basalts from the area of Confederation Peak, Can. J. Earth Sci., 5, 1–21, 1968. Baker, B. H., P. A. Mohr, L. A. J. Williams, Geology of the eastern rift system of Africa, Geol. Soc. Amer., 1971. Barberi, F., S. Borsi, G. Ferrara, G. Marinelli, J. Varet, Relationships between tectonics and magmatology of the northern Afar (or Danakil) Depression, Phil. Trans. Roy. Soc. London, A267, 293–311, 1970. Battey, M. H., The 'two-magma theory' and the origin of ignimbrites, Bull. Volcan., 29, 407–424, 1966. Cole, J. W., Gariboldi volcanic complex, Ethiopia. Bull. Volcan., 33, 566–578, 1969. Comucci, P., Le vulcaniti del lago Tana (Africa Orientale), Atti. Accademia Nazionale Lincei (Roma), 209, 1950. Gass, I. G., Evolution of volcanism in the junction area (of the Red Sea, Gulf of Aden and Ethiopian rifts), Phil. Trans. Roy. Soc. London, A267, 369–381, 1970. Gibson, I. L., Origin of some Icelandic pitch-stones, Lithos, 2, 343–349, 1969. Girdler, R. W., J. D. Fairhead, R. C. Searle, W. T. C. Sowerbutts, Evolution of rifting in Africa, Nature, 224, 1178–1182, 1969. Gouin, P., Seismic and gravity data from Afar in relation to surrounding areas, Phil. Trans. Roy. Soc. London, A267, 338–358, 1970. Green, D. H., A review of experimental evidence on the origin of basaltic and nephelinitic magmas, Phys. Earth Planet. Interiors, 3, 221–235, 1970. Harkin, D. A., The Rungwe volcanics at the northern end of Lake Nyasa, Mem. Geol. Surv. Tanganyika, II, 172, 1960. Harris, P. G., Zone refining and the origin of potassic basalts, Geochim. Cosmochim. Acta, 12, 195–208, 1957. Harris, P. G., Basalt type and African rift tectonism, Tectonophysics, 8, 427–436, 1969. Hurley, P. M., Absolute abundance and distribution of Rb, K and Sr in the Earth, Geochim. Cosmochim. Acta, 32, 273–283, 1968. Lacroix, A., Les roches hyperalcalines du massif du Fantale et du Col de Balla (Abyssinie), Mem. Soc. Geol. Fr., 6, 89–102, 1930. Laughton, A. S., The Gulf of Aden, Phil. Trans. Roy. Soc. London, 259A, 150–171, 1966. Le Bas, M. J., P. A. Mohr, Feldspathoidal rocks from the Cainozoic volcanic province of Ethiopia, Geol. Rundsch., 58, 273–280, 1968. Le Bas, M. J., P. A. Mohr, Tholeiite from the Simien alkali basalt centre, Ethiopia, Geol. Mag., 1970. Lipman, P. W., Alkalic and tholeiitic basaltic volcanism related to the Rio Grande depression, southern Colorado and northern New Mexico, Geol. Soc. Amer. Bull., 80, 1343–1354, 1969. Macdonald, R., I. L. Gibson, Pantelleritic obsidians from the volcano Chabbi (Ethiopia), Contrib. Miner. Pet., 24, 239–244, 1969. Manasse, E., Contribuzioni allo Studio Petrografico della Colonia Eritrea, 169, Siena, 1909. McBirney, A. R., Andesitic and rhyolitic volcanism of orogenic belts, The Earth's Crust and Upper Mantle, Geophysical Monograph, 13 P. J. Hart, 501–507, American Geophysical Union, Washington, D. C., 1969. McBirney, A. R., I. G. Gass, Relations of oceanic volcanic rocks to mid-oceanic rises and heat flow, Earth Planet. Sci. Lett., 2, 265–276, 1967. McKenzie, D. P., D. Davies, P. Molnar, Plate tectonics of the Red Sea and East Africa, Nature, 226, 243–248, 1970. Mohr, P. A., The Ethiopian rift system, Bull. Geophys. Obs. Addis Ababa, 3serial no. 5, 33–62, 1962. Mohr, P. A., The Ethiopian Cainozoic lavas—a preliminary study of some trends: spatial, temporal, and chemical, Bull. Geophys. Obs. Addis Ababa, 3serial no. 6, 103–144, 1963. Mohr, P. A., The Ethiopian rift system, Bull. Geophys. Obs. Addis Ababa, 11, 1–65, 1967. Mohr, P. A., The Cainozoic volcanic succession in Ethiopia, Bull. Volcan., 32, 5–14, 1968. Mohr, P. A., The Afar triple junction and sea-floor spreading, J. Geophys. Res., 75, 7340–7352, 1970a. Mohr, P. A., Plate tectonics of the Red Sea and East Africa—a comment on the paper by McKenzie et al., 1970, Nature, 228, 547–548, 1970b. Mohr, P. A., Catalogue of chemical analyses of rocks from the intersection of the African, Gulf of Aden, and Red Sea rift systems, Smithsonian Contrib. Earth. Sci., 2, 269, 1970c. Molly, E., Études pétrographiques en Ethiopie: 3, observations sur les roches alcalines d'Abyssine, C. R. Soc. Phys. Hist. Nat. Genève, 51, 76–79, 1934. Niazi, M., Crustal thickness in the central Saudi Arabian Peninsula, Geophys. J., 15, 545–547, 1968. Nixon, P. H., L. Clark, The alkaline centre of Yelele and its bearing on the petrogenesis of other eastern Uganda volcanoes, Geol. Mag., 104, 455–472, 1967. Pagliani, G., Pantelleriti e basalti di Gimma (A. O. I.), Rend. R. Ist. Lombardi Sci. Lett., 123, 33–43, 1940. Raisin, C. A., Petrological notes on rocks from southern Abyssinia, Quart. J. Geol. Soc. London, 59, 292–306, 1903. Saggerson, E. P., L. A. J. Williams, Ngurumanite from southern Kenya and its bearing on the origin of rocks in the northern Tanganyika alkaline district, J. Petrol., 5, 40–81, 1964. Schilling, J.-G., Red Sea floor origin: Rare-earth evidence, Science, 165, 1357–1359, 1969. Sigurdsson, H., The Icelandic basalt plateau and the question of sial, Iceland and Mid-Ocean Ridges S. Björnsson, Soc. Sci. Islandica, 38, 32–49, 1967. Sowerbutts, W. T. C., Crustal structure of the East African plateau and rift valleys from gravity measurements, Nature, 223, 143–146, 1969. Sutherland, D. S., Potash-trachytes and ultra-potassic rocks associated with the carbonatite complex of the Toror Hills, Uganda, Mineral. Mag., 35, 363–378, 1965. Tazieff, H., J. Varet, Signification tectonique et magmatique de l'Afar septentrional (Ethiopie), Rev. Geog. Phys. Geol. Dynam., 11, 429–450, 1969. Tramontini, C., D. Davies, A seismic refraction survey in the Red Sea, Geophys. J., 17, 225–241, 1969. Weber, M., Die petrographische Ausbeute der expeditionen O. Neumann-v. Erlanger nach Ostafrika und Abessynien 1900–1901, Mitt. Munchen Geog. Gesellsch., 1, 637–660, 1906. Williams, L. A. J., Volcanic associations in the Gregory Rift Valley, East Africa, Nature, 224, 61–64, 1969. Williams, H., A. R. McBirney, Volcanic history of Honduras, Univ. Calif. Publ. Geol. Sci., 85, 101, 1969. Wright, J. B., Petrographic sub-provinces in the Tertiary to Recent volcanics of Kenya, Geol. Mag., 102, 541–557, 1965. Citing Literature Volume76, Issue810 March 1971Pages 1967-1984 ReferencesRelatedInformation