Résumé
Orogenic processes, including metamorphism and deformation, can significantly impact the interpretation, understanding and economic value of mineral deposits. Critical metals and metalloids (CMs) such as gallium (Ga), germanium (Ge), indium (In), platinum group elements (PGE), and cobalt (Co) are commonly mined as byproducts of base metals (i.e., Zn, Fe, Cu, Ni). The impact of metamorphism on CMs (re)distribution is frequently overlooked, underestimated or not investigated by adequate and representative analytical procedures. In this review article, we evaluate the importance of metamorphism and deformation on the remobilization of CMs. The timing of ore emplacement relative to orogen formation, mineralogy and ore textures of ca. 170 deposits reported in the literature have been extracted in three continental districts (Australia, China, and Europe). This synthesis shows that metamorphism frequently overprints ore deposits and might create favorable conditions for the redistribution of CMs within ore minerals. Orogenic minerals rich in CMs can be broadly defined as the large-scale remobilization or sample-scale redistribution product of pre-existing CMs concentrations, present in the primary ore, driven by metamorphism and/or tectonic processes. Contrasting behaviors for the formation of orogenic minerals rich in CMs is described in the literature. Under low-to medium-grade conditions (<450 • C; <2-3kbar), Ge-rich orogenic minerals are generally well preserved while In, Co-PGE-rich orogenic minerals form newly at higher temperature (> 450 • C). In several sulfides potentially rich in CMs, experimental and natural observations have demonstrated ductile behavior at low grades (~100-200 • C; <2kbar), which may affect the distribution of CMs in sulfide ore. This review highlights the challenges ore geologists face in apprehending primary signatures in sulfide minerals within systems affected by secondary orogenic events as well as the potential of CMs system analysis in understanding the conditions of ore (de)formation.