Geochemistry and geochronology of wolframite and scheelite from the Zhuxi W(Cu) polymetallic deposit, South China

The factors controlling tungsten mineralization type dominated by scheelite or wolframite are still not well constrained. The Zhuxi tungsten–copper deposit is dominated by scheelite mineralization, yet recently-discovered orebodies in depth contain wolframite-bearing veins in which wolframite is locally replaced by scheelite. To constrain genetic association and precipitation mechanisms of the two types of W minerals, we conducted in situ U–Pb dating and trace elemental analyses of wolframite and scheelite. The results show that wolframite is dated at 151.9 ± 1.9 Ma, whereas scheelite has ages of 150.2 ± 5.0 Ma. Additionally, both wolframite and scheelite at Zhuxi show elevated Y/Ho (32.07–84.05) and decreased Zr/Hf (0–12.35) ratios, deviating from charge and radius controlled (CHARAC) behavior. Combined with low Mo contents and positive Eu anomalies in scheelite, and the local presence of fluorite coexisting with scheelite, we propose that W minerals at Zhuxi were precipitated from an F-rich, low f O 2 magmatic hydrothermal fluid. In addition, wolframite occurs as hübnerites with Mn/(Mn + Fe) ratios of 0.59–0.80 and is closely associated with scheelite. These features suggest the following evolutionary sequence: an F-rich fluid exsolved from highly fractionated granites initially suppressed scheelite precipitation; with progressive cooling, Mn-rich wolframite precipitated; subsequently, interaction between the fluid and carbonate wall rocks caused a sharp increase in Ca activity, triggering scheelite precipitation in direct contact with Mn-rich wolframite. This model demonstrates that tungsten mineral assemblage at Zhuxi records a dynamic interplay between fluid composition, temperature evolution, and host-rock reactivity, rather than being controlled by lithology alone.