Evidence for Archaean lamprophyre from the Kaapvaal Craton, South Africa

Prevec, Stephen A. and Anhaeusser, Carl R. and Poujol, Marc (2004) Evidence for Archaean lamprophyre from the Kaapvaal Craton, South Africa. South African Journal of Science, 100 (11 & 12). pp. 549-555. ISSN 0038-2353

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Abstract

A suite of mafic dykes occurs as a late component in a wellcharacterized trondhjemite–tonalite–diorite–granodiorite assemblage in the Johannesburg Dome of the central Kaapvaal Craton, southern Africa. The dykes have been subdivided into two sets, based on their orientation, and major and trace element geochemistry. Set 1 dykes are characterized by elevated SiO2, Al2O3 and TiO2, and particularly by enriched LILE and HSFE (e.g. Zr > 200 ppm, Nb > 20 ppm, Ba > 300 ppm), higher than in any of the accompanying felsic rocks. REE and trace element values for Set 1 dykes are similar to those for calc-alkaline lamprophyres. The Set 2 dykes have similar trace element distributions, but are significantly less enriched in general, and are broadly tholeiitic in composition, with enriched MgO (>11 wt.%) indicative of an olivine–phyric tholeiitic basaltic protolith. Field relationships and available U–Pb zircon geochronology indicate that the dykes are contemporaneous with components of the trondhjemitic host rocks, and with late granodiorites. The geochemical, geochronological and field petrological setting indicates partial melting of basaltic and eclogitic lithosphere at c. 3120 Myr ago in the basal Kaapvaal Craton, and subsequent emplacement into pre-existing c. 3430 Myr tonalitic to dioritic crust.

Item Type:Article
Additional Information:Rhodes Centenary issue
Uncontrolled Keywords:mafic dykes, Johannesburg Dome, Kaapvaal Craton, South Africa
Subjects:Y Unknown > Subjects to be assigned
Divisions:Faculty > Faculty of Science > Geology
ID Code:107
Deposited By: Rhodes Library Archive Administrator
Deposited On:25 Aug 2005
Last Modified:06 Jan 2012 16:17
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