Fe–Pb–Zn Zonation and Overprinting in the No. VI Ore Block of the Galinge Skarn Deposit, East Kunlun: Constraints from Geochemistry of Two Intrusive Pulses and Ore-Mineral Trace Elements

The No. VI ore block of the Galinge skarn system in the Qimantagh metallogenic belt, East Kunlun, contains proximal Fe-oxide mineralization and distal Pb–Zn sulfide mineralization that are spatially zoned and locally overprinted along faults and interlayer fracture zones. To constrain the controls on Fe–Pb–Zn zonation and overprinting within this ore block, we integrated LA–ICP–MS zircon U–Pb dating, zircon Lu–Hf isotopes, whole-rock major and trace elements, and in situ trace elements of magnetite, pyrite, chalcopyrite, pyrrhotite, and arsenopyrite. Zircon U–Pb ages indicate two Indosinian intrusive pulses: an early granodiorite at 235.1 ± 0.51 Ma and a younger granodiorite–quartz diorite at 229.52 ± 0.46 Ma. Excluding the hydrothermally altered sample ZK26804-805, the intrusive rocks are metaluminous, medium- to high-K calc-alkaline I-type granitoids mainly derived from remelting of ancient crustal material, with a greater juvenile crustal or mantle contribution in the younger phase. Magnetite is generally Zn-rich and Pb-poor, whereas late pyrite and chalcopyrite are enriched in Pb, Ag, Cd, and Bi; local Sb–As anomalies in magnetite and arsenopyrite indicate late hydrothermal overprinting. The Fe and Pb–Zn mineralization is best interpreted as staged products of one multipulse magmatic–hydrothermal system controlled not only by intrusive pulses but also by inherited structural pathways, host-rock reactivity, and evolving redox-sulfidation conditions. The interpretation of Sb–As enrichment in magnetite is therefore used cautiously because these elements may occur as lattice substitutions and/or micro- to nano-inclusions introduced or modified during retrograde alteration.