Geochronology and Geochemical Characteristics of Mineralized and Barren Intrusions in the Fengyan Porphyry‐Skarn Zn‐Pb‐Mo Deposit, Central Fujian Region, and their Metallotectonic Implications

Abstract Porphyry‐skarn deposits are genetically associated with multistage intrusive complexes. However, their ore fertility varies markedly, as exemplified by the coexistence of mineralized and barren intrusions within a single pluton. The factors controlling this disparity, particularly whether high oxygen fugacity ( f O 2 ) and volatile‐rich magmas are essential, remain poorly constrained. This study investigates the Fengyan Zn‐Pb‐Mo deposit in the central Fujian region by comparing geochronological and geochemical features of ore‐associated granite porphyry and barren monzogranite. SIMS zircon U‐Pb dating reveals the mineralized intrusion crystallized at 142.5 ± 1.6 Ma, significantly later than the barren monzogranite (150.3 ± 1.3 Ma). The ore‐associated porphyry exhibits higher magma temperatures and sulfur contents, yet lower f O 2 and water content relative to the barren monzogranite. Hf‐O isotopes reveal greater mantle input in the ore‐related granite porphyry ( ε Hf ( t ) = –11.5 to –7.5; δ 18 O = 6.50‰ to 7.11‰) than in the ore‐barren monzogranite ( ε Hf ( t ) = –16.0 to –9.5; δ 18 O = 6.81‰ to 8.00‰). Furthermore, elevated f O 2 and volatile‐rich conditions are not prerequisites for Zn‐Pb‐Mo mineralization, implying other factors are key. The barren rock formed during low‐angle subduction of the Paleo‐Pacific plate, whereas the mineralized porphyry originated during slab rollback and lithospheric extension. This study highlights that medium–low f O 2 (mean ΔFMQ +0.39 in granite porphyry vs. +1.80 in monzogranite), volatile‐poor magmatic systems in extensional settings can form significant mineralization, offering new insights for exploration in central Fujian and analogous regions.