Spatial and Temporal Variations in Scheelite Composition Record Fluid Evolution Pathways in the Yongping Cu-W Skarn Deposit, South China

Abstract The trace element composition of scheelite has been widely used to constrain the temporal evolution of ore-forming fluids; however, its spatial compositional variations remain poorly understood. This study addresses this gap by integrating cathodoluminescence (CL) imaging, in situ U-Pb dating, trace element geochemistry, and Sr-Nd isotopic analyses of four types of scheelite from the proximal skarn and distal carbonate replacement deposit (CRD) ore bodies of the Yongping Cu-W skarn deposit, South China. U-Pb ages of scheelite from the proximal skarn and distal CRD ore bodies are 155.5 ± 3.4 Ma and 153.4 ± 1.8 Ma, respectively, indicating that W mineralization coincides with the emplacement of spatially associated Late Jurassic biotite granite porphyry. Scheelite trace element profiles across the deposit reveal decreasing Mo concentrations and Mo/Sr ratios, accompanied by increasing U, Sr, Re, and δEu from proximal to distal zones. We interpret that these compositional trends are influenced by progressive fluid-rock interaction, temperature, and pH along the fluid flow path. Correspondingly, scheelite from the proximal skarn ore exhibits lower 87Sr/86Sr ratios (0.716261–0.720616), whereas scheelite from the distal CRD ore shows higher values (0.721162–0.723463), further supporting enhanced interaction between magmatic fluids and sedimentary wall rocks in distal settings. In contrast, initial ɛNd(t) values of scheelite range widely from –26.7 to –11.2 and do not correlate with the variation of 87Sr/86Sr ratios, suggesting that fluorite precipitation in proximal and distal locations may have modified Sm/Nd ratios and introduced Nd from the wall rock. These results demonstrate that the trace element and Sr isotopic composition of scheelite can serve as effective tracers of fluid evolution and flow direction, which may also be useful for exploration vectoring.