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Schonland Research Centre, University of the Witwatersrand, P.O. Wits 2050, South Africa, email: hart{at}schonlan.src.wits.ac.za
Department of Earth Sciences, Cardiff University, P.O. Box 914, Cardiff CF1 3YE, email: iain{at}earth.cf.ac.uk
Department of Geological Sciences, University of Cape Town, Rondebosch 7700, South Africa, email: mtd{at}geology.uct.ac.za, maarten{at}cigc.uct.ac.za
Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, D.C., 20015, USA., email: carlson{at}dtm.ciw.edu
South African Nuclear Energy Corporation, P. O. Box 582, Pretoria, 0001, South Africa, email: marco{at}necsa.co.za
Geology and Geophysics Department., University of Utah 135S 1460E Salt Lake City, UT 84112-0111 USA, email: demoser{at}mines.utah.edu
School of Geosciences, University of the Witwatersrand, Private bag 3, Wits 2050, South Africa, email: ashwall{at}geosciences.wits.ac.za
Granulites exposed in the core of the Vredefort Dome are generally thought to represent components of the Archean middle crust of the central Kaapvaal Craton. These rocks were exhumed from depths of at least 20 km following an ~2.02 Ga meteorite impact event, exposing a "crust on edge" section believed to represent a continuous magmatically-differentiated sequence from upper crust possibly down to Moho. Platinum group element concentrations suggest that mafic and ultramafic enclaves in the lower most sections are fragments of greenstone belt material metamorphosed at granulite grade. Re/Os isotopic data are consistent with previously published U-Pb zircon data, which suggest that the mafic and ultramafic rocks have a primary age of ~3.5 Ga and were metamorphosed to granulite grade at ~3.1 Ga. However, near the core of the Vredefort Dome across a major shear zone, other ~3.5 Ga greenstone belt remnants are at distinctly lower metamorphic grade. The juxtaposition of mafic-ultramafic rocks with a different metamorphic history in the core of the Vredefort structure requires a modified "crust on edge" model that incorporates tectonic stacking of different crustal segments at ~3.1 Ga.
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