Geology and geochronology of Inaccessible Island, South Atlantic

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Authors:Chevallier, L.; Rex, D. C.; Verwoerd, W. J.
Author Affiliations:Primary:
Univ. Stellenbosch, Dep. Geol., Stellenbosch, South Africa
Univ. Leeds, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 129(1), p.1-16. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:1992
Note:In English. 19 refs.; illus. incl. 48 anal., 1 table, sect., sketch maps
Summary:Inaccessible Island (part of the Tristan da Cunha group) is the eroded remnant of an extinct volcano dominated by flows of alkaline olivine basalt. The oldest stratigraphic unit is a hydrothermally altered basement of questionable early Pliocene (6.5 m.y.) age (by K-Ar method). This is overlain by a volcanic superstructure built during the last 3 m.y. 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 m.y. may be spurious and their relationship with the second volcanic stage is uncertain. Reliable age determinations of 0.95-0.72 m.y. were obtained on lava flows of the second stage, the latest of which include benmoreite, trachyte and rhyolite. The main volcanic centre was located immediately offshore and was attached to an E-W volcanic rift zone. [C.H.D.]
Subjects:Age; Areal geology; Chemical composition; Igneous rocks; Volcanic rocks; Atlantic Ocean Islands; Tristan da Cunha; Inaccessible Island
Abstract Numbers:92M/3450
Record ID:1992036994
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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