ARCHEAN AND PROTEROZOIC MINERALIZATION AND TECTONICS AT THE RENCO MINE - NORTHERN MARGINAL ZONE, LIMPOPO BELT, ZIMBABWE

Gold mineralization at the Renco mine occurs within the northern margi nal zone of the Limpopo belt along east-northeast-trending structures that formed in the Late Archean (2.6 Ga Pb-Pb step leach age on syntec tonic garnet) under granulite facies. The mineralization is hosted by a massive enderbite which intruded at 2.57 Ga (U-Pb zircon age). North -northeast-trending pyroxenite dikes were intruded around 2.4 Ga (Pb-P b step leach age of garnet and pyroxene), probably associated with the intrusion of the Great Dyke and satellites. The northern marginal zon e had been exhumed to crustal levels corresponding to greenschist faci es by this time. The major gold-bearing pyrrhotite-chalcopyrite +/- bi smuth mineralization occurred under greenschist facies conditions (< 4 00 degrees C). This occurred at similar to 2.0 Ca as deduced from cool ing of biotite associated with mineralization (1.88 Ga Rb-Sr age). Thi s ca. 2.0 Ga age of the mineralization implies a link with the importa nt Early Proterozoic tectono-thermal event in the Limpopo belt during which shearing occurred under greenschist facies conditions in the Tri angle shear zone. The Renco deposit is not, as formerly suggested, a h igh-grade mineralization, although there is some evidence for a precur sory, high-grade phase of mineralization in the Late Archean. Its gene sis is quite distinct from most of the greenstone associated deposits of the Zimbabwe craton, which are known or inferred to be Late Archean in age.