Sulfur isotopic characteristics of the Zhaxikang Sb-Pb-Zn-Ag deposit in southern Tibet

The Zhaxikang Sb-Pb-Zn-Ag deposit is the only super-large deposit in the North Himalayan Metallogenic Belt, but its genesis is debated. Genetic models include hot springs, magmatic-hydrothermal fluids and sedimentary exhalative overprinted by hydrothermal fluids. Here, we present sulfur isotopic data to constrain the genetic models for this deposit. The delta(34)S(V-CDT)values of sulfides in the first pulse of mineralisation range from 7.8 to 12.2 parts per thousand (average = 10.7 parts per thousand), and in the second pulse of mineralisation have lower delta S-34 values of 4.5-11.3 parts per thousand (average = 8.5 parts per thousand), suggesting the sulfur source for the first pulse of mineralisation is mainly seawater sulfur mixed with some mantle-derived sulfur, whereas the second pulse of mineralisation originated from mantle-derived sulfur and sulfur from earlier formed sulfides and wall rocks. Together with previously published Fe-Zn-Cd isotope evidence for the Zhaxikang deposit and regional S isotopic and geochronological data, the new data suggest that the first pulse of mineralisation is related to multiple seafloor volcanic events during the synsedimentary period (220-130 Ma) with submarine hydrothermal sedimentation (metasomatism) genesis that is overprinted by the second pulse of mineralisation associated with the magmatic-hydrothermal activity during the post-collision period (25 Ma to now).