Geochemistry and Genetic Significance of Scheelite in the Nanwenhe Tungsten Deposit, Yunnan Province, Southwestern China

The Nanwenhe tungsten deposit is located in the southeastern Yunnan Laojunshan mineral district and is hosted in the Paleoproterozoic Mengsong Group strata. It can be divided into two periods and four stages: skarn (early and late) and the vein type (feldspar–quartz–scheelite–tourmaline and calcite. There are two types of scheelite occurrences: one in skarn (Sch-1) and the other in feldspar–quartz–scheelite–tourmaline veins (Sch-2). The latter is further divided into two types: Sch-2a and Sch-2b. The REE content and Eu anomaly of skarn scheelite (Sch-1) are affected by early mineral crystallization; Sch-2a in feldspar–quartz–scheelite–tourmaline veins forms in a Na+-rich environment, and Eu2+ released into the fluid through hydrolysis may have largely entered tourmaline, resulting in the weak positive Eu anomaly of Sch-2a; the negative Eu anomaly of Sch-2b is likely inherited from the metamorphic fluid. The mineralization is likely closely related to the metamorphic fluid activity generated by the tensional structural environment at the end and after the regional uplift, forming ore by reducing fluids associated with regional metamorphism. The Laojunshan mineral district hosts several tungsten and tin polymetallic deposits and occurrences that share similar geological characteristics with the Nanwenhe tungsten deposit. No granite bodies related to mineralization have been identified within the mining area. Therefore, research on the genesis of the Nanwenhe tungsten deposit holds significant value for guiding exploration efforts.