Element redistribution during hydrothermal evolution of the Dexing porphyry Cu deposit: Insights from geochemistry, XRD, and μXRF mapping

• Quartz-sericite alteration hosts the principal Cu-Mo-Au mineralization in the Dexing porphyry system. • As, Bi, Cs, and S provide effective geochemical vectors for porphyry Cu exploration. • Integrated mass-balance calculations and high-resolution µXRF mapping quantitatively reveal hydrothermal overprints and element redistribution. Recognition of hydrothermal alteration and element mobility patterns in porphyry systems is critical for understanding ore-forming processes and developing effective exploration vectors. The Dexing porphyry Cu-(Mo-Au) deposit, with proven resources of 9.7 Mt Cu, 0.4 Mt Mo, and 265 t Au and representing the largest porphyry deposit in eastern China, offers an ideal case for investigating hydrothermal evolution and metal redistribution in a large porphyry system. This study integrates petrography, whole-rock geochemistry, X-ray diffraction (XRD), quantitative mass-balance calculations, and high-resolution micro-X-ray fluorescence (μXRF) mapping to investigate the spatial distribution of hydrothermal alteration and element mobility in two representative drill cores from the Tongchang orebody. The results reveal a systematic alteration sequence from early potassic alteration to quartz-sericite and outer chlorite-sericite alteration. Quantitative mass-balance calculations demonstrate distinct alteration-related element mobility patterns. The potassic zone exhibits enrichment in Fe 2 O 3 T, K 2 O, SO 3 , Ag, Cu, Au, and W, accompanied by depletion of CaO, Na 2 O, and Ni. The quartz-sericite zone shows strongest enrichment in Cu and Mo, together with enrichment in SiO 2 , Fe 2 O 3 T, K 2 O, SO 3 , Ag, Au, As, Bi, and W, indicating intense fluid-rock interaction and major ore-metal precipitation during this stage. In contrast, the chlorite-sericite zone displays moderate enrichment in Fe 2 O 3 T, MgO, K 2 O, SO 3 , Ag, Cu, Au, Mo, As, Bi, W, and Zn, reflecting distal and lower temperature hydrothermal overprinting. High-resolution μXRF mapping further constrains the spatial relationships among alteration minerals, sulfide veins, and ore-forming elements, revealing that Cu-Mo mineralization is closely associated with quartz-sericite alteration and commonly overprints earlier potassic assemblages. Elements such as As, Bi, Cs, and S exhibit mobility patterns comparable to Cu and Mo and may therefore serve as useful pathfinder elements for exploration. The integrated application of mass-balance calculations and μXRF mapping provides an effective workflow for quantifying hydrothermal overprints, tracking metal redistribution, and distinguishing ore-related alteration domains in complex porphyry systems.