ARCHEAN RAPAKIVI GRANITE ANORTHOSITE RHYOLITE COMPLEX IN THE WITWATERSRAND BASIN HINTERLAND, SOUTHERN AFRICA

The Gaborone granite suite and the Kanye Formation formed during a sin gle magmatic event in the late Archean evolution of the Kaapvaal crato n, southern Africa, and may be the oldest rapakivi granite-anorthosite -rhyolite suite in the world. The Gaborone granite suite underlies an area of >6000 km2 in the northwestern part of the craton and comprises A-type rapakivi granite, leucogranite, granophyric microgranite, and minor anorthosite. It is partly surrounded by the Kanye Formation, a 1 000-m-thick pile of pyroclastic and flow-banded rhyolitic lava. Precis e U-Pb dating of granitic and granophyric components of the Gaborone s uite and rhyolite of the Kanye Formation shows that all three rock typ es are the same age within error (2783-2785 Ma). Emplaced in the sourc e area during upper Witwatersrand Supergroup sedimentation, the Gaboro ne-Kanye event has important implications for the tectonic and magmati c evolution of the northern Kaapvaal craton and possibly also played a n important role in the development of the adjacent auriferous sedimen ts.