Geology, isotopes and geochronology of the Caijiaping Pb–Zn deposit in the North Wuyi area, South China: Implications for petrogenesis and metallogenesis

The Caijiaping Pb–Zn deposit is a recently discovered subvolcanic hydrothermal deposit in the North Wuyi area. Its mineralization is generally distributed at the contact of rhyolite porphyry and sandstone, and in the interlayer crushed zone of Early Jurassic sandstone. Sulfide minerals in this deposit mainly consist of abundant sphalerite, galena, pyrite and chalcopyrite. Silicification, chloritization and sericitization are widely developed and closely related to the Pb–Zn mineralization. The δ34S values of early dark brown sphalerite (marmatite), main-stage sphalerite and galena (− 1.1–2.5‰, average 0.83‰) suggest that the sulfur was mainly sourced from a magmatic system. Lead isotope ratios in the sulfide minerals, rhyolite porphyry and sandstone are relatively homogeneous (206Pb/204Pb = 17.786–18.612, 207Pb/204Pb = 15.504–15.635, 208Pb/204Pb = 38.115–38.798), and are compatible with metamorphic rocks of Mesoproterozoic Zhoutan Group (Wuyi metamorphosed basement). Early Jurassic sandstone, deposited in an active continental margin or continental arc setting, exhibits low textural maturity and displays geochemical similarities to the Zhoutan Group. The rhyolite porphyry, with features of volcanic arc granite, also shows an affinity with the Zhoutan Group. SIMS zircon U–Pb dating shows that the rhyolite porphyry was emplaced at 156.0 ± 1.2 Ma, indicating that Caijiaping mineralization formed later than 156 Ma. Hf isotope compositions of the rhyolite porphyry [εHf(t) = − 14.3 to − 8.5, average − 10.6] imply that it was mainly derived from reworking of ancient crust. Potassium feldspar selected from felsic veins within the ore-cutting F4 fault yields a 40Ar/39Ar age of 120.0 ± 4.0 Ma, indicating that the Pb–Zn mineralization formed before 120 Ma. Therefore, the age of mineralization is bracketed between 156 and 120 Ma. Combined with regional geological information, we propose that the Caijiaping mineralization mainly formed from magmatic hydrothermal processes in a regionally extensional setting, and the Wuyi metamorphosed basement significantly contributed to diagenetic and metallogenic processes in this deposit.