Structural and compositional constraints on the emplacement of the Bushveld Complex, South Africa

The Bushveld Complex was emplaced and cooled in less than one million years – results of zirconology, and geotectonic implications

“…This upward push could have caused active pumping of magma, which formed and ponded during the previous melting event with storage in numerous melt pockets throughout the SCLM and/or at the crust-mantle boundary. In addition, upward push could have caused re-activation of large fault zones in the crust such as at the Thabazimbi-Murchison-Lineament (e.g., Clarke et al, 2009), which enabled fast ascent of large volumes of mafic magma with high flux into the crust, finally resulting in the extremely fast accretion of the Bushveld magma chamber. It is likely that the Bushveld magma chamber formed at a much faster rate than magma production within the mantle, as has been suggested previously by Silver et al (2006).…”

SHRIMP U–Pb zircon age for the Segwagwa–Masoke Igneous Complex of southeastern Botswana and implications for the deformation history of the Achaean to Proterozoic Transvaal Supergroup of southern Africa

“…In the region, deformation in this time frame coincides with granulite facie metamorphism during the Magondi orogeny at ca. 2.03 Ga or with the tectonothermal activity in the Limpopo belt, which may have affected the western margin of the Kaapvaal-Zimbabwe craton (Barton et al, 1994;Munyanyiwa et al, 1995;Holzer et al, 1998Holzer et al, , 1999Majaule et al, 2001;Mapeo et al, 2001;Clarke et al, 2008). The linkage with deformation during the Magondi orogeny is consistent with the fact that the upper Transvaal and Magondi Supergroup sedimentary rocks have the same age of deposition (Mapeo et al, 2001(Mapeo et al, , 2006a and were therefore deformed at about the same time at ca.…”

“…1927 Ma, probably during the closing of the Magondi basin in the north-eastern Botswana or as a consequence of geodynamic conditions created by the collision between the Zimbabwe and Kaapvaal cratons documented between ca. 2.05 and 2.0 Ga in the Limpopo belt (Barton et al, 1994;Munyanyiwa et al, 1995;Holzer et al, 1998Holzer et al, , 1999Mapeo et al, 2001;Majaule et al, 2001;Ranganai et al, 2002;Zeh et al, 2007;Clarke et al, 2008). The Magondi orogeny represents a major Palaeoproterpozoic subduction event, which, based on collision rift tectonic models, may have led to the reactivation of the Limpopo belt leading to the emplacement of the Bushveld Complex and its satellite intrusions in southern Africa (Silver et al, 2004).…”

“…A major pre-Bushveld deformation event is favoured for much of the deformation seen in the Transvaal (Bushveld) Basin, whilst in the Griqualand West basin folding and thrusting of Transvaal rocks is thought to pre-date the Namaqua Kibaran tectonothermal events (Altmann and Hälbich, 1991). The concept of pre-Bushveld deformation for much of the Transvaal Supergroup implies that a greater portion of the Bushveld Igneous Complex is largely undeformed by tectonic compression but exhibits structures related to diapiric magmatic growth (Uken and Watkeys, 1997;Clarke et al, 2008), although the overall lobe shape of the Bushveld Complex has also been linked to tectonic deformation (Buchanan et al, 1999 and references therein) whilst other workers suggests the post-Bushveld deformation in the Transvaal Supergroup was in response to the development of the ca. 2.0 Ga Vrederfort Dome (Courtenage et al, 1995).…”

Abstracts

“…The Zebediela fault forms a constituent part of the major Thabazimbi-Murchison Lineament array that separates the eastern and northern limbs and is thought to control magmatic facies distribution in the Bushveld Complex (Clarke et al, 2009). The greatest thickness of the Lower Zone throughout the whole Complex, was up to 1700 m. This was reported for the Grasvally area Rock types: The main rock types in the Lower zone include dunite, harzburgite, olivine pyroxenite, pyroxenite and feldspathic pyroxenite that form cyclic units of variable thickness.…”