Microstructure and trace element occurrence in molybdenite (MoS2) from the Dexing ore field: Implications for the differential enrichment of rhenium

Rhenium (Re), a critical metal of significant importance to national security and military strategies, has garnered extensive attention in recent years. Most of the world’s rhenium is extracted from molybdenite in porphyry deposits. As the primary host-mineral of Re, molybdenite (MoS₂) is a layered sulfide mineral featuring two hexagonally coordinated sulfur layers enclosing a molybdenum layer. Molybdenite, a mineral commonly found in hydrothermal ore deposits, is similar to other layered minerals in that it exhibits polytypism. Nevertheless, the nanoscale distribution and enrichment mechanisms of rhenium (Re) within molybdenite remain largely enigmatic. This research utilizes high-resolution transmission electron microscopy (HRTEM), in combination with the nanobeam techniques, to explore the occurrence and variable enrichment of rhenium (Re) in molybdenite extracted from the Fujiawu and Tongchang deposits within the Dexing ore field, eastern China, where notably diverse average rhenium contents are observed. The molybdenite polytypes identified in the Dexing ore field encompass 2H₁ and 2H₁ + 3R, whereas those from Fujiawu are categorized as 2H₁ and 2H_d, and those from Tongchang as 2H₁, 3R and 2H_d and 3R_d. The disordered molybdenite from the Dexing ore field formed under non-equilibrium conditions, with molybdenite from Fujiawu displaying a higher degree of orderliness compared to that from Tongchang. Rhenium is found adsorbed on the surface of molybdenite from the Dexing ore field in the form of Re-S complexes. By comparing the trace element compositions and microstructures of molybdenite from the Fujiawu and Tongchang deposits, we ascribe the differential enrichment of Re predominantly to the microstructures of molybdenite, the impurity content of ore-forming fluids, the rates of cooling and crystallization during molybdenite formation.