矿床地球化学国家重点实验室知识库

Located in the northern Guangdong Province, the Dabaoshan Pb–Zn polymetallic massive sulfide deposit is one of the most important regions to have produced Fe, Cu, Pb, Zn and S in southern China. While much progress has been made with respect to the geology and geochemistry of the deposit, a better understanding of ore genesis is warranted. This ore body contains abundant bismuth element, only few studies exist on the distribution characteristics and existing states of bismuth. Electron microprobe study yields that native bismuth, tellurides (e.g. hedleyite) and sulfide minerals, are the main forms in which this element is found. The occurrence and characteristics of native bismuth and its mineral assemblages are different with high-T gold-bearing deposits, but are more similar to those of mid-low temperature hydrothermal deposits. Our research shows that the Bi(Te) at Dabaoshan derived from the Late Yanshanian dacite porphyry. The Bi(Te)-rich ore-forming fluid developed during intrusion of the dacite and mineralized along fractures, and overprint the earlier Pb–Zn mineralization. During the early overprinting event, the ore-forming fluid was rich in Bi and Te and poor in S, under uniform mid-temperature conditions. As the hydrothermal fluids evolved, they became enriched with Ag and Pb. Sulfur was rich in the fluid during the late overprinting event; this may have been related to dissolution of sulfide. The low abundances of Bi, Te and Ag in sulfide minerals (e.g., galena and sphalerite), indicate that ore genesis and the ore-forming materials were different between the Pb–Zn and Bi–Te–Ag stages. Thus, new geological and geochemical data were used to delineate the sequence ore genesis of Dabaoshan Pb–Zn mineralization.