Magmatism and mineralization of the Taolin Pb–Zn–Cu deposit in the Mufushan area, central Jiangnan Orogen (South China): Insightfvs from zircon U–Pb and sphalerite Rb–Sr geochronology, and H–O–S–Pb isotope geochemistry

Abstract

The large Taolin Pb–Zn–Cu deposit contains 0.98 Mt Pb + Zn @ 2.35 % and 0.04 Mt Cu @ 0.1 %, and is associated with the Mufushan granitic complex in the central Jiangnan Orogen (JNO), South China. It consists of sulfides in hydrothermal veins, resulting from three successive mineralization stages (I–III). However, the geochronology of mineralization and ore-related granite, and sources of ore-forming fluids and materials are not well defined. Here we present zircon U–Pb dating for granite, Rb–Sr age of sphalerite, and H–O–S–Pb isotopes for ores that served to constrain the magmatism and mineralization at Taolin better. Zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) dating of the biotite monzogranite gave an age of 136 ± 0.8 Ma (MSWD = 1.8). Furthermore, an Rb–Sr isochron of sphalerite separates yielded an age of 135.4 ± 2.6 Ma (MSWD = 1.0). These results suggest that the intrusion of biotite monzogranite and Pb–Zn–Cu mineralization are contemporaneous with a close temporal relationship. δDH2O values of quartz samples from stage II range from –67.4 % to –62.5 % and calculated δ18OH2O values from –4.1 % to –1.8 ‰, indicating a mixing source of magmatic fluids and meteoric water for ore-forming fluids. S and Pb isotopic compositions of sphalerite and galena from stage II support the genetic relationship between the Pb–Zn–Cu mineralization and biotite monzogranite at Taolin and probably indicate a common source. However, previous high δ34S values (12.6 ‰ to 17.7 ‰) for barite from stage III suggest the involvement of high sulfur isotopes, which could be derived from gypsum layers within the Early-Middle Triassic sedimentary strata. The ore-related biotite monzogranite, with εHf(t) values ranging from –6.8 to –3.0 and two-stage Hf model ages ranging from 1625 to 1383 Ma, was probably derived from Neoproterozoic lower crust with a minor injection of the asthenospheric mantle. Geochronological and isotopic data demonstrate a magmatic-hydrothermal origin for the Taolin Pb–Zn–Cu deposit.