<p>Both tungsten (W) and tin (Sn) are crust-affiliated elements that tend to concentrate in highly fractionated granitic magmas. However, their mineralization is often decoupled, with some intrusions hosting predominantly W deposits while others being enriched in Sn. The mechanisms controlling this W-Sn mineralization decoupling remain unclear. This study investigates the role of fluorine (F) in this process by examining W-and Sn-mineralized granites in the Nanling Range, South China, with key findings as follows: (1) Sn-mineralized granites generally exhibit higher F contents (up to several thousand ppm) than W-mineralized granites (100–700 ppm), representing high-F and moderate-F magmatic systems, respectively. (2) Elevated F enhances the solubility of H₂O and chlorine (Cl) in silicate melts, which inhibits fluid exsolution and premature Sn extraction, thereby enabling Sn enrichment in highly evolved melts to form Sn deposits. In moderate-F systems, early fluid exsolution at deep crustal levels leads to Sn loss in the form of stable Sn-Cl complexes to the fluid phase, leaving residual melts to form W-dominated deposits. (3) The higher F content in Sn-related magmas is attributed to inputs of volatiles associated with mantlederived mafic magmas. (4) Sn-mineralized granites can be classified as crust-mantle hybrid “H-type” granites associated with the flux of mantle-derived melt across trans-crustal magmatic systems. In contrast, W-mineralized granites are predominantly crust-derived “C-type” granites produced by either heat-induced melting (magmatic underplating) or decompression melting with limited mantle contribution. We propose that the difference in F content essentially governs W-Sn mineralization decoupling. Future research should focus on the identification of deep mantle halogen reservoirs beneath Sn-polymetallic provinces and experimental investigations into the geochemical behavior of halogens, W, and Sn in magmatic-hydrothermal systems.</p>