A review of the characteristics and geological settings of orogenic gold deposits of the Boule Mossi Domain: implication for gold exploration

This paper reviews the geological characteristics and settings of orogenic gold deposits in the Boule Mossi Domain of West Africa. Understanding the geological characteristics of these deposits is crucial for effective gold exploration in the region. Some of the gold deposits of the Birimian of West Africa were formed during the Eoeburnean magmatic accretion cycle and, more generally, during the tectonic accretion and reworking phases of the Eburnean orogenic cycle. The deposits are controlled by first-order structures, but in most cases are located within second order structural discontinuities. The auriferous fluid found within these deposits is CO2-rich with intermediate salinities. The CO2-rich fluids may have originated from the thermal breakdown of organic materials in deeply buried biogenetic carbonaceous rocks. The nature of the hydrothermal sulphide complexes suggests that the most probable source of the gold is the metamorphic devolatilization of the underlying metasedimentary rocks. The strong association between mineralization and structural discontinuities, as well as the distinguishable mineralogical and isotopic mineralization signatures in the Birimian, lends itself to a variety of techniques in gold exploration such as machine learning and stable isotope geochemistry. This review has important implications for the exploration of orogenic gold deposits in western Africa.