Exhumation of Limpopo Central Zone granulites and dextral continent-scale transcurrent movement at 2.0 Ga along the Palala Shear Zone, Northern Province, South Africa

The Palala Shear Zone is part of a major tectonic lineament in southern Afr ica, which extends over 1000 km from central Botswana to the Soutpansberg i n South Africa. The lineament is situated between the Central Zone of the L impopo Belt and the Kaapvaal Craton. At its main exposure, in the Koedoesra nd Window 50 km E of Ellisras, Northern Province, the Palala Shear Zone com prises a c. 15 km wide mylonite zone which can be subdivided into a Norther n, Central and Southern Domain. This study addresses the tectono-metamorphi c history of the Palala Shear Zone in the Koedoesrand Window and its role i n the tectonics of the Limpopo Belt. In order to do this, structural and pe trographical work was combined with geochronology. Age data from relic mine ral parageneses show that metapelites from the Central Domain underwent gra nulite facies metamorphism around 2.6 Ga. However, because of an intense Pr oterozoic overprint, field relationships of the Archean event are largely d isrupted. During a second high-grade event at c. 2.0 Ga, granulite facies m etamorphism was reached in the Northern Domain and the adjacent Limpopo Cen tral Zone. Charnockites were emplaced in the Northern Domain after 2.1 Ga a nd were affected by retrograde amphibolite and greenschist facies metamorph ism around 1.97 Ga. Post-orogenic transcurrent faulting under (sub)greensch ist facies conditions characterizes the Central and Southern Domains. Field observations and microstructural investigations indicate a dextral shear s ense for the retrograde mylonitisation. These findings document that the Pa lala Shear Zone played an important role during the exhumation of the Prote rozoic granulites in the Limpopo Central Zone, associated with a transpress ive orogeny between 2.05 and 1.95 Ga. Low-grade post-orogenic transcurrent faulting in the Palala Shear Zone at c. 1.9 Ga may be associated with the t ranstensional opening of the Soutpansberg and Palapye grabens. On the basis of the tectono-metamorphic history in the Koedoesrand Window and regional geophysical, geochemical and sequence-stratigraphic data, the Palala Shear Zone is interpreted as a Proterozoic suture zone, along which the Archean K aapvaal and Zimbabwe Provinces were juxtaposed. (C) 1999 Elsevier Science B .V. All rights reserved.