Isotopic (H-O-S-Pb) geochemistry and zircon U-Pb geochronology of the Kaladaban Pb-Zn deposit, in Xinjiang, NW China

The Kaladaban Pb-Zn-Cu volcanogenic massive sulphide deposit (VMS), located within the Altyn region of Xinjiang in NW China, is an economically significant deposit with known reserves of 414,400 t Zn with a grade of 4.14%, 265,200 t Pb with a grade of 2.52%, and 149,200 t Cu with a grade of 1.10%. The mineralization is hosted in basalt, rhyolite, and rhyolite porphyry, with the latter two rock types yielding zircon U-Pb ages of 516 and 505 Ma, respectively, representing the timing of crystallization. Samples of the host volcanic rocks show fractionated rare-earth element (REE) patterns and enrichment in both large-ion lithophile elements (e.g., Ba, Rb, U, and light REEs) and high-field-strength elements (e.g., Th, Hf, and Zr). These features are similar to those of oceanic island basalt. delta O-18 values of ore fluids from quartz in orebodies range from +8.1 parts per thousand to +13.4 parts per thousand, and fluid delta D-18(water) values vary from -68.5 parts per thousand to -99.1 parts per thousand, indicating a mixture of magmatic hydrothermal and seawater. delta S-34 values range from +8.5 parts per thousand to +14.9 parts per thousand, suggesting that S that in the Kaladaban ore minerals had a mixed origin of magmatic hydrothermal fluids and sulphate-reduced seawater. Ratios of Pb-206/Pb-204, Pb-207/Pb-204, and Pb-208/Pb-204 from metal minerals in Kaladaban deposit are 18.513-18.740, 15.633-15.727, and 38.236-38.398, respectively, indicating extremely radiogenic characteristics, similar to the host volcanic rocks. We infer that the Kaladaban Pb;Zn deposit formed in an active continental margin setting related to southward subduction of the North Altyn oceanic crust during the early Palaeozoic.