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Geology and geochronology of Inaccessible Island, South Atlantic

Published online by Cambridge University Press:  01 May 2009

L. Chevallier ,
D. C. Rex  and
W. J. Verwoerd
L. Chevallier
Affiliation:
Department of Geology, University of Stellenbosch, Stellenbosch 7600, South Africa
D. C. Rex
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
W. J. Verwoerd
Affiliation:
Department of Geology, University of Stellenbosch, Stellenbosch 7600, South Africa
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Abstract

Inaccessible Island is the eroded remnant of an extinct, comparatively small intraplate volcano dominated by flows of alkaline olivine basalt. The oldest stratigraphie unit is a hydrothermally altered basement of somewhat questionable early Pliocene (6.5 Ma) age. This is unconformably overlain by a volcanic superstructure built up during the last three million years. The two formations have different trace element signatures that may be attributed to different mantle sources. Boulders of gabbro are common but the presence of an in situ plutonic intrusion could not be confirmed. Their K-Ar age of 12.8 Ma may be spurious and their possible relationship with the volcano is uncertain. Reliable age determinations of 0.95–0.72 Ma were obtained on lava flows of the second volcanic stage, subdivided into four units or stratigraphie members. The latest unit consists of plugs, sills and flows of an evolved magma fraction (benmoreite and trachyte) of which benmoreite is considered to be the more voluminous. Several dyke swarms of different ages reveal the internal structure of the volcano. It is concluded that the main volcanic centre was located immediately offshore to the northwest and that the edifice was attached to an east–west volcanic rift zone. Apart from marine erosion, massive land-sliding probably took part in shaping the island and its submarine platform.

Type
Articles
Information
Geological Magazine , Volume 129 , Issue 1 , January 1992 , pp. 1 - 16
Copyright
Copyright © Cambridge University Press 1992

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References

Baker, P. E., Gass, I. G., Harris, P. G. & Le Maitre, R. W. 1964. The volcanological report of the Royal Society Expedition to Tristan da Cunha, 1962. Philosophical Transactions of the Royal Society of London, Series A 256, 439–578.Google Scholar
Briden, J. C., Rex, D. C., Faller, A. M. & Tomblin, J. F. 1979. K–Ar geochronology and palaeomagnetism of volcanic rocks in the Lesser Antilles island arc. Philosophical Transactions of the Royal Society of London, Series A 291, 485–528.Google Scholar
Chevallier, L. 1986. Tectonics of Marion and Prince Edward volcanoes (Indian Ocean): result of regional control and edifice dynamics. Tectonophysics 124, 155–75.CrossRefGoogle Scholar
Chevallier, L. 1987. Tectonic and structural evolution of Gough volcano: a volcanological model. Journal of Volcanology and Geothermal Research 33, 325–36.CrossRefGoogle Scholar
Chevallier, L. & Bachelery, P. 1981. Evolution structurale du volcan actif du Piton de la Fournaise, Ile de la Réunion, Océan Indien Occidental. Bulletin Volcanologique 44, 723–41.CrossRefGoogle Scholar
Chevallier, L. & Vatin Perignon, N. 1982. Volcano-structural evolution of Piton des Neiges, Reunion Island, Indian Ocean. Bulletin Volcanologique 45, 285–98.CrossRefGoogle Scholar
Chevallier, L. & Verwoerd, W. J. 1987. A dynamic interpretation of Tristan da Cunha volcano, South Atlantic Ocean. Journal of Volcanology and Geothermal Research 34, 35–49.CrossRefGoogle Scholar
Cliff, R. A., Baker, P. E. & Mateer, N. J. in press. Geochemistry of Inaccessible Island volcanics. Chemical Geology.Google Scholar
Dunne, J. C. 1941. Volcanology of the Tristan da Cunha group: results of the Norwegian Scientific Expedition to Tristan da Cunha, 1937–1938. Oslo, Norske Videnskaps Akademi 2, 1–145.Google Scholar
Fornari, D. 1987. The geomorphic and structural development of Hawaiian submarine rift zones. In Volcanism in Hawaii, vol. 1 (eds Decker, R. W., Wright, T. L. and Stauffer, P. H.), pp. 125–32. U.S. Geological Survey Professional Paper no. 1350.Google Scholar
Gass, I. G. 1967. Geochronology of the Tristan da Cunha Group of Islands. Geological Magazine 104, 160–70.CrossRefGoogle Scholar
Krafft, M. 1982. L'éruption volcanique du Karthala en avril 1977 (Grande Comore, Oceacute;an Indien). Comptes Rendus de l'Académie des Sciences de Paris 294, 753–8.Google Scholar
Le Maitre, R. W. 1984. A proposal by the IUGS subcommission on the systematics of igneous rocks for a chemical classification of volcanic rocks based on the total alkali silica (TAS) diagram. Australian Journal of Earth Sciences 31, 243–55.Google Scholar
Maund, J. G., Rex, D. C., Le Roex, A. P. & Reid, D. L. 1988. Volcanism on Gough Island: a revised stratigraphy. Geological Magazine 125, 175–81.CrossRefGoogle Scholar
Preece, R. C., Bennett, K. D. & Carter, J. R. 1986. The Quaternary paleobotany of Inaccessible Island (Tristan da Cunha group). Journal of Biogeography 13, 1–33.Google Scholar
Strong, D. F. & Jacquot, C. 1970. The Karthala caldera. Grande Comore. Bulletin Volcanologique 34, 663–80.CrossRefGoogle Scholar
Swales, M. K., Sidall, C. P., Mateer, N. J., Hall, H. N., Preece, R. C. & Fraser, M. W. 1985. The Denstone expedition to Inaccessible Island. The Geographical Magazine 151, 347–50.CrossRefGoogle Scholar
Treuil, M., Joron, M. & Jaffrezic, H. 1982. Géochimie du manteau: distribution des éléments en traces dans les magmas basaltiques. Part II. Proposition l'une méthode l'identification des effets de source et de distinction de ceux de la fusion partielle et de la différenciation des magmas. Exemples des domaines l'expansion océanique. Journal of Radioanalytical Chemistry 71, 347–63.Google Scholar
Verwoerd, W. J. 1971. ‘Geology.’ In Marion and Prince Edward Islands and map (eds Van Zinderen Bakker, E. M. and Dyer, R. A.), pp. 40–62. Balkema: Cape Town.Google Scholar