Porphyry Mo and distal Zn-Pb mineral system: An example of the Fengyan Zn–Pb–Mo deposit in central Fujian, SE China

Abstract

Central Fujian is an important Zn-Pb-Ag-Cu-Mo-Au mineral province in southeastern China, yet the polymetallic mineralization is still disputed between Proterozoic volcanogenic massive sulfide (VMS) or Mesozoic skarn type. The Fengyan is representative of the deposit type in central Fujian, characterized by shallow-level stratabound Zn-Pb mineralization and deep-level porphyry Mo mineralization. The ores are mainly hosted by Meso-Neoproterozoic marble and schists. Detailed field investigation, petrographic observation, and electron probe microanalysis indicate that the stratabound Zn-Pb ore host comprises a contact metamorphic/metasomatic suite. LA-ICP-MS zircon U-Pb dating of the granite porphyry yielded a weighted mean 206Pb/238U age of 145.0 ± 1.0 Ma (n = 17, MSWD = 0.97). Hydrothermal titanite grains in the stratabound Pb–Zn ores (intergrown with epidote and galena) yielded a weighted mean 207Pb-corrected 206Pb/238U age of 147.3 ± 4.4 Ma (n = 32, MSWD = 0.45), whilst molybdenite from the concealed Mo orebody has a Re–Os model age of ca. 145.3 to 145.5 Ma. Meanwhile, the molybdenite Re content and the published S-Pb isotope evidence indicate a crust source with minor mantle input. The largely similar age (within error) and ore-material source indicate that the Fengyan mineral system comprises an intrusion-proximal porphyry-type Mo mineralization and intrusion-distal Zn-Pb mineralization. This study proposes a genetic model for the mineral system, which would have important implications for exploring concealed porphyry Mo or Cu-Mo deposits, and/or their related magmatic-hydrothermal systems beneath/beyond these Zn-Pb(-Ag) deposits in central Fujian.