Early Precambrian crustal development; changing styles of mafic magmatism

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doi: 10.1144/gsjgs.150.4.0625
Authors:Hall, R. P.; Hughes, D. J.
Author Affiliations:Primary:
University of Portsmouth, Department of Geology, Portsmouth, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.150 (Part 4), p.625-635. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1993
Note:In English. 127 refs.; illus. incl. sketch map
Summary:There is growing evidence that, with certain clear provisions, the principle of uniformitarianism can be applied as equally to the early Precambrian as it can through the rest of the geological record. In terms of mafic magmatism, there are similarities between some ancient and modern suites, both intrusive and extrusive, but there are also some major differences, such as the presence of komatiites in the Archaean and the formation of large- scale layered intrusions and extensive dyke swarms at the end of the late Archaean and in the early Proterozoic. The mantle has evolved continuously with the progressive extraction of mafic magmas but, allowing for this, continental tholeiites appear to have changed little with time. The geochemistry of mafic volcanic rocks occurring in many greenstone belts suggests a continental contamination component and that these volcanic rocks are most closely akin to those from present-day arc systems. The relative abundance of early Precambrian intrusive mafic suites reflects the global crustal accretion-differentiation superevent towards the close of the Archaean. Bimodal tholeiitic-noritic mafic magmatism associated with many of these intrusive suites stems from this rapid turnover in the mantle-mafic crust-continental crust system. This, in turn, may give a link between the respective evolution of Archaean to Recent komatiitic, noritic and boninitic suites. [R.A.H.]
Subjects:Accretionary wedges; Andesites; Archean; Basalts; Boninite; Chemical composition; Crust; Gabbros; Igneous rocks; Komatiite; Mafic composition; Norite; Ophiolite; Plutonic rocks; Precambrian; Ultramafic composition; Volcanic rocks; Evolution; Igneous activity
Abstract Numbers:94M/1132
Record ID:1993027239
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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