Early Precambrian basic rocks of Africa

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Authors:Smith, H. S.
Author Affiliations:Primary:
Univ. Cape Town, Dep. Geochem., Cape, South Africa
Volume Title:Early Precambrian basic magmatism
Volume Authors:Hall, R. P., editor; Hughes, D. J.
Source:Early Precambrian basic magmatism, edited by R. P. Hall and D. J. Hughes, p.352-378. Publisher: Chapman and Hall, New York, NY, United States
Publication Date:1990
Note:In English; illus. incl. 5 tables, geol. sketch maps
Summary:There is very little information that can be condensed out of the Archaean rocks in Africa to imply a uniform tectono-magmatic evolution. A summary is given for African Archaean mafic and ultramafic metavolcanic rocks. Reliable ages have been established for only two greenstone belts, namely, the Belingwe (approx 2700 m.y.) and Barberton (approx 3500 m.y.). Other well established ages include the Pongola supergroup and Usushwana intrusives in the Kaapvaal craton and the Great Dyke in Zimbabwe. In most Archaean cratons in Africa at least two ages of greenstone belt formation have been identified, and three occur in the Zimbabwe craton. In the Kaapvaal craton the situation is not so clear. Until recently most greenstone fragments were considered in terms of the Barberton model and were thought to be of similar age to the Barberton greenstone belt. However, there may be two ages of greenstone development within the Barberton belt and it now appear that the Barberton 'model' is no longer applicable to other greenstone belt assemblages. Geochronological information for other greenstones in the Kaapvaal craton is not sufficiently well constrained at present to establish any clear history of the early to mid Archaean evolution of this terrain. After the craton stabilized at approx 3000 m.y., the sequence of geological events is more clearly established to the end of the Archaean. [J.M.H.]
Subjects:Absolute age; Archean; Dates; Distribution; Greenstone belts; IGCP; Igneous rocks; Mafic composition; Metamorphic belts; Petrology; Precambrian; Terranes; Africa; Igneous activity
Abstract Numbers:91M/2105
Record ID:1991002619
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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