Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Prendergast, M.D. Articles by Wingate, M.T.D. Search for Related Content GeoRef GeoRef Citation

Zircon geochronology and partial structural re-interpretation of the late Archaean Mashaba Igneous Complex, south-central Zimbabwe

Guesachan, Shielhill Road, Kirriemuir, Angus DD8 4PA, Scotland, United Kingdom, e-mail: marprend{at}hotmail.com

M.T.D. Wingate

Geological Survey of Western Australia, 100 Plain St., East Perth, WA 6004, Australia, and Tectonics Special Research Centre, School of Earth and Geographical Sciences, University of Western Australia, WA 6004, Australia, e-mail: michael.wingate{at}doir.wa.gov.au

Ion microprobe (SHRIMP) U-Pb zircon dating has determined the age of a gabbroic enclave within the supraregional intrusive komatiitic Mashaba Igneous Complex (MIC) to be 2743 ± 11 Ma and that of an interpreted comagmatic thick differentiated komatiitic flow within the adjacent Mashava-Masvingo greenstone belt to be 2754 ± 13 Ma. Recent geological observations support a revised structural interpretation of the MIC as an assemblage of three separate horizontal layered sills emplaced almost coevally at two different crustal depths: the chromititiferous Prince Sill intruded concordantly, and prior to regional folding, into the basal sedimentary rocks of the late Archaean Upper Bulawayan Supergroup, the relatively thin and evolved West Sill within early Archaean greenstone and gneissic basement, and the major Northwest Arm-Main Sill mainly within adjacent basement gneiss. The sill assemblage was vertically linked via ultramafic dykes and, as previously proposed, was fed through the dyke-like Northeast Arm, whose overlying layered rocks are here interpreted as correlatives of the Northwest Arm-Main Sill. The new precise age for the MIC is 50 Ma years older than the former geological estimate of ~2.7 Ga. The comparable date for the volcanic phase supports the interpretation of both as component phases of a putative Masvingo W komatiitic sill-flow complex but is incompatible with interpretation of the late Archaean lithostratigraphy of the Mashava-Masvingo belt as a thrust-stacked package of unrelated continental and oceanic rocks.

This article has been cited by other articles:

				M. D. Prendergast Archean Komatiitic Sill-hosted Chromite Deposits in the Zimbabwe Craton Economic Geology, August 1, 2008; 103(5): 981 - 1004. [Abstract] [Full Text] [PDF]