Constraining the fluid source of late-stage Cu-Au vein-type mineralization in the Danyore Valley, Kohistan Island Arc, Pakistan: New perspectives from quartz geochemistry

Quartz veins in the Danyore Valley prospect of the Kohistan Island Arc, northern Pakistan, host Cu-Au-bearing sulfide assemblages and provide a useful archive of hydrothermal fluid evolution. Previous geochemical, zircon geochronological, and Ssingle bondPb isotopic studies have constrained the emplacement and geodynamic evolution of mineralized Mesozoic granitoid intrusions, but the sources of the fluids and ore-forming components, as well as the evolution of the ore-forming system, remain poorly understood. This study integrates petrography, scanning electron microscope cathodoluminescence (SEM-CL) imaging, and in situ LA-ICP-MS trace-element analysis of quartz veins hosted mainly in Early Cretaceous intrusions at the Danyore Valley Cusingle bondAu prospect. Four quartz generations (Qz-1 to Qz-4) are identified. The earliest generation (Qz-1) is weakly luminescent and texturally homogeneous; Qz-2 shows oscillatory growth zoning and records renewed quartz precipitation; Qz-3 forms the main vein-filling quartz and is locally cut and sealed by bright, fracture-controlled Qz-4. Chalcopyrite, pyrite, and bornite, and the associated Cusingle bondAu mineralization, are spatially associated only with Qz-4. Trace-element data indicate that Qz-1 to Qz-3 are generally Ti-poor (medians 0.86, 1.24 and 0.11 ppm, respectively), have low base-metal contents, and have Al/Ti and Ge/Al ratios consistent with precipitation from evolved, low-salinity metamorphic (orogenic-style) fluids. Elevated Cu (median 323 ppm) and high Au (up to 118 ppm) in the Qz-4 domains, together with their bright CL response, sharp cross-cutting relationships, and association with sulfides, indicate that Qz-4 records the principal metal-introducing stage. Fluid cooling and possible boiling, accompanied by the loss of volatile components such as CO2 and H2S, may have destabilized metal-ligand complexes and promoted the precipitation of Cu-Au-bearing sulfides. Combined with published sulfur and lead isotope data, these observations suggest that one or more pulses of metal-bearing hydrothermal fluids overprinted an earlier, barren metamorphic-hydrothermal vein system. We therefore interpret the Danyore Valley prospect as a structurally controlled quartz–sulfide vein system with a late magmatic-hydrothermal, possibly porphyry-related, Cusingle bondAu overprint; a distal position within a concealed porphyry system cannot be excluded on present evidence.