The age and petrology of the Chimbadzi Hill Intrusion, NW Zimbabwe: first evidence for early Paleoproterozoic magmatism in Zimbabwe

Manyeruke, T. D., Blenkinsop, Thomas G., Buchholz, P., Love, D., Oberthur, T., Vetter, U. K. and Davis, D. W. 2004. The age and petrology of the Chimbadzi Hill Intrusion, NW Zimbabwe: first evidence for early Paleoproterozoic magmatism in Zimbabwe. Journal of African Earth Sciences 40 (5) , pp. 281-292.

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Abstract

The mafic-ultramafic Chimbadzi Hill intrusion in the NW of the Zimbabwe craton is a dyke with inward-dipping margins comprising magnetite peridotite, troctolite and magnetite melatroctolite. The magnetite peridotite is composed of about equal amounts of V- and Ti-bearing magnetite and olivine (∼Fo60). The troctolite is composed of about 50% olivine (∼Fo50-54), 40% plagioclase (An53-58), 7% clinopyroxene and minor apatite and magnetite with ilmenite lamellae. Geochemical trends suggest that the Chimbadzi Hill Intrusion formed by fractional crystallisation from a single initial magma. However, the more primitive magnetite peridotite overlies the more evolved troctolite in the intrusion. This ‘apparent’ inverted stratigraphy may be due to emptying of a fractionated magma chamber from the top, or to floor subsidence during intrusion. U–Pb dating on baddeleyite reveals that the age of the Chimbadzi Hill Intrusion is 2262 ± 2 Ma. This age does not correspond to any known tectono-thermal event in the Zimbabwe Craton or adjacent metamorphic belts. It is ∼300 Ma younger than the late Archean Great Dyke, and ∼230 Ma older than other Paleoproterozoic events in and around the craton. Therefore, it may represent a so far undocumented very early Proterozoic igneous event in the Zimbabwe Craton. The intrusion represents a vanadium resource for Zimbabwe, with titanium potentially being mined as by-product.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Ocean Sciences
Subjects:	Q Science > QE Geology
Uncontrolled Keywords:	Fractional crystallisation; Intrusion; Magnetite peridotite; Troctolite Paleoproterozoic; Mafic-ultramafic complex; Cumulate
Publisher:	Elsevier
ISSN:	1464-343X
Last Modified:	04 Jun 2017 05:18
URI:	http://orca.cf.ac.uk/id/eprint/50610

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