Metallogeny of early Precambrian granulite facies terrains

Abstract

Few mineral deposits have been found in Early Precambrian granulite facies terrains and there are widespread beliefs that even if there were mineral concentrations in these high grade areas these would have been destroyed or dispersed by the metamorphic-tectonic processes. However, the paucity of mineralization is actually a function of the poor exposure and the structural-stratigraphic-metamorphic complexity, and the general opinion is that these areas are not promising targets for mineral exploration. A survey of the literature indicates that many economic mineral deposits are located in Early Precambrian granulite facies terrains and are found in rock associations that are common to unmetamorphosed and lower grade metamorphosed ores in Early Precambrian granite-greenstone areas. Ores of mafic-ultramafic associations are common (Selebi-Pikwe, Cu, Ni, Botswana), those of felsic (anorthosite) associations are widespread (Fiskenaesset, Cr, Greenland), and Fe concentrations of sedimentary affiliations are found in the banded iron formations (Imataca, Venezuela) and similar Mn ores (Kodur, India). Stratiform sulphides of marine-volcanic associations are important (Broken Hill, Pb, Zn, Australia) and stratabound ores of sedimentary affiliation are known (Ookiep, W, South Africa).