The large Zijinshan high-sulfidation epithermal Cu-Au deposit, together with the adjacent Luoboling porphyry Cu-Mo deposit, constitutes a major porphyry-epithermal ore district in South China. Current debate centers on whether the Zijinshan and the adjacent Luoboling deposits are cogenetic or represent separate ore-forming events, which is a question of importance for exploration in the district. In this contribution, the magmatichydrothermal history of the relationship between Zijinshan and Luoboling is reconstructed based on new alunite ⁴⁰Ar/³⁹Ar ages from Zijinshan and zircon U-Pb ages of ore-related intrusions from both deposits. This study has been complemented by S isotope analysis on the dated alunite to assess their origin. Three types of coexisting alunite and sulfide assemblages exist at Zijinshan, namely, (1) alunite-quartz-covellite cemented breccias; (2) alunite-digenite veins and (3) banded alunite-pyrite veins. Their field occurrences and S isotope features suggest a magmatic-hydrothermal origin for alunite-quartz-covellite cemented breccias and alunite-digenite veins, whereas the origin of alunite-pyrite veins is likely to be related to magmatic steam. Given the intimate textural coexistence between sulfides and alunite, four undisturbed ⁴⁰Ar/³⁹Ar plateau ages obtained from alunite-quartz-covellite cemented breccia and alunite-digenite vein-type alunite define the timing of Zijinshan high-sulfidation mineralization from 102.86 ± 0.61 to 101.19 ± 0.60 Ma. These agree with bracketing zircon U-Pb ages of pre-ore dacite porphyry at 104.8 ± 0.9 Ma and 104.7 ± 0.5 Ma and a zircon U-Pb age of a post-ore granite porphyry dike at 99.5 ± 0.7 Ma. Combined with their field occurrences, the four alunite ages imply two discrete hydrothermal pulses and a possible time span of over 500 k.y. for the overall high-sulfidation mineralization. Two alunite samples from alunite-pyrite veins yield a slightly disturbed ⁴⁰Ar/³⁹Ar plateau age at 101.67 ± 0.61 Ma and an apparently undisturbed age at 99.91 ± 0.59 Ma, probably reflecting partial or complete thermal resetting related to the coeval granite porphyry dikes. At Luoboling, zircon U-Pb analysis yields an age of 133.6 ± 1.1 Ma for a dark, ore vein-bearing quartz-diorite porphyry sample and confirms the petrographic observation that they are xenoliths of early wall rocks for the porphyry mineralization. A granodiorite porphyry sample with abundant A-veins is interpreted as an intermineral porphyry phase, dated at 106.5 ± 1.4 Ma. This age is interpreted as the upper limit for porphyry Cu-Mo mineralization and agrees well with previously reported molybdenite Re-Os and biotite ⁴⁰Ar/³⁹Ar ages, which collectively suggest porphyry Cu-Mo mineralization and potassic alteration at Luoboling were formed within the interval between ca. 106 and 104 Ma. Taken together, the age of the Zijinshan high-sulfidation mineralization is substantially younger than the porphyry mineralization at Luoboling, and we conclude that there is no direct genetic link between the two deposits. However, the Zijinshan Cu-Au deposit is temporally associated with the deep porphyritic granodiorite, which gives zircon U-Pb ages from 102.1 ± 0.8 to 101.8 ± 0.5 Ma, overlapping with the alunite ⁴⁰Ar/³⁹Ar ages for the high-sulfidation mineralization. This finding has important implications for the ongoing exploration for the two mineralization types in the ore district and elsewhere.

The large-scale Maoping W–Sn deposit in the Gannan metallogenic belt of the eastern Nanling Range, South China, spatially associated with the Maoping granite pluton, hosts total ore reserves of 103,000 t WO₃ and 50,000 t Sn. Two different types of mineralization developed in this deposit: Upper quartz vein-type mineralization, mostly within the Cambrian metamorphosed sandstone and slate, and underneath greisen-type mineralization within the Maoping granite. Cassiterites from both types of mineralization coexist with wolframite. Here we report for the first time in situ U–Pb data on cassiterite and zircon of the Maoping deposit obtained by LA-ICP-MS. Cassiterite from quartz vein and greisen yielded weighted average ²⁰⁶Pb/²³⁸U ages of 156.8 ± 1.5 Ma and 156.9 ± 1.4 Ma, respectively, which indicates that the two types of mineralization formed roughly at the same time. In addition, the two mineralization ages are consistent with the emplacement age of the Maoping granite (159.0 ± 1.5 Ma) within error, suggesting a close temporal and genetic link between W–Sn mineralization and granitic magmatism. The two types of mineralization formed at the same magmatic-hydrothermal event. Cassiterite from both types of mineralization shows high Fe, Ta, and Zr contents with a low Zr/Hf ratio, suggesting that the ore-forming fluid should be derived from the highly differentiated Maoping granite pluton. Cassiterite in greisen has higher contents of Nb and Ta but a lower concentration of Ti compared with that in quartz vein, indicating that the formation temperature of greisen-type mineralization is little higher than that of quartz-vein-type mineralization.