A Comparison Between the Metamorphism of the Cameros Basin (Spain) and the Witwatersrand Gold Field (South Africa). Metallogenetic Implications

The Witwatersrand Coldfield (WCF) and the Cameros Basin (CB) were subjected to widespread fluid flow during metamorphism. Physical conditions reached at the thermal peaks have been estimated at 1 kb and 340°C in the case of the CB and 1-2kb and 350 ± 50°C in the WCF (i.e. subgreenschist and greenschist facies conditions). In both cases the infiltrating fluids were predominantly of deep intra-basinal and metamorphic origin and the fluid flow was focused along zones of enhanced permeability (pervasive cleavage, shear zones, fractures and bedding). Phyrophillite and chloritoid are common minerals in the internal parts of the metamorphic areas. Cold and U, accompanied by organic matter, were introduced late in the WGF; In the CB no evidence still exist of this economically important event. In the two basins, metamorphism is post-depositional, 300 to 600 Ma younger in the Archean WGF, and inmediatly subsequent in the case of the Mesozoic CB . In this case a relationship with a first stage of basin inversion seems probable. The many similarities between metamorphism in the two basins and the new model of hot migrating fluid-driven metamorphism invoked in both cases, open room for new prospecting strategies of metals of echonomic interest in the C