Geological bases and types of gold in carbonate deposits of the Birimian stage in West Africa

Abstract

Relevance. The Paleoproterozoic region of the West African craton (WAC) includes numerous world-class gold deposits. These deposits are located in belts of volcanic and volcanic-sedimentary Birimian greenstone rocks. Gold mineralization of the orogenic type is spatially, chronologically, and genetically associated with the compression stage in the northwest and southeast. Several deposits are located in more or less unaltered and deformed zones west of Côte d’Ivoire (Guinea) and the Keniba–Kedugou Senegal-Mali salient. To date, the role of this type of rocks from the standpoint of the model of “local structural traps” for hydrothermal and (or) metamorphogenic gold-bearing fluids remains underestimated. The purpose of the research. The purpose and objectives of the research are to study and reveal the relationship of precious metal mineralization with regional and provincial geotectonic events, igneous and volcanic rock complexes of different ages, types of metamorphic and metasomatic transformation of ore-bearing rocks and types of ores within the West African Сraton. Particular attention is paid to the origin and location of gold mineralization in the carbonate formations of the lower (early) Birimian dating up to 2.12 billion years. Conclusions. The author demonstrates the differences between the Proterozoic gold mineralization of the preorogenic and, in fact, orogenic stages of the geological development of West Africa (Burkina Faso, Ghana) from modern regional-geological, geohistorical and metallogenic positions. The results of our own research have shown and proved the endogenous nature of the precious metal mineralization of the region. This is especially important for gold ores in sedimentary carbonate strata, which for a long time were considered syngenetic (placer).