Genesis of the Huanggoushan Pb-Zn-Au polymetallic deposit in southern Jilin Province, NE China: Constraints from fluid inclusions and C-H-O-S-Pb isotope systematics

摘要

The Huanggoushan Pb-Zn-Au deposit is located in the central part of southern Jilin Province in northeastern portion of the North China Craton. It experienced two types of mineralization, namely, stratabound Pb-Zn mineralization placed close to interlayer fracture zones of banded marble and veined Au mineralization controlled by NNE-trending brittle-ductile shear zones. The Pb-Zn mineralization is characterized by a low-temperature and low-salinity H2O-NaCl system of hydrothermal fluids that yielded delta D and delta O-18(H2O) values similar to those of meteoric water. The delta S-34 values of sulfide minerals in the Pb-Zn ores range from 14.8 parts per thousand to 17.1 parts per thousand with an average of 16.1 parts per thousand, which reflects a sulfur origin in the seawater sulfate. The sulfur of Pb-Zn ores was most possibly transformed from that of sulfate S6+ into the sulfide S2- by bacteriogenic sulfate reduction processes. Lead isotopic compositions of sulfides separated from the Pb-Zn ores show Pb-206/Pb-204 ratios from 15.309 to 16.353, Pb-207/Pb-204 ratios from 15.321 to 15.485, and Pb-208/Pb-204 ratios from 34.883 to 35.550. By contrast, original medium-high-temperature hydrothermal fluids in stage I of the Au mineralization are represented by low-salinity H2O-CO2-NaCl system with relatively higher delta D and delta O-18(H2O) values, which indicates that original ore-forming fluids were possibly sourced from the Mesozoic magmatic fluids. The delta C-13 values of fluid inclusions in hydrothermal quartz from Au ores range from -9.6 parts per thousand to -2.4 parts per thousand, most values of which are similar to those of magmas. The sulfides in Au ores have relatively lower delta S-34 values of 1.0 parts per thousand to 8.0 parts per thousand than those of sulfides in the Pb-Zn ores. The various delta S-34 values of sulfides from the Au ores, similar to those of sulfides from the Mesozoic magmatic hydrothermal Au deposits in Heilongjiang-Jilin region, reflect a magmatic sulfur origin. Lead isotopic compositions of sulfides from the Au ores have relatively higher ratios, with Pb-206/Pb-204 from 17.852 to 20.468, Pb-207/Pb-204 from 15.591 to 15.833, and Pb-208/Pb-204 from 37.051 to 38.899. Collectively, geology, fluid inclusions, and isotope geochemistry suggest that ore-forming fluids of the Pb-Zn mineralization originated from heated seawater with sulfur and lead sourced from seawater sulfate and upper crust, respectively. Thus, the Pb-Zn mineralization can be classified as the Paleoproterozoic SEDEX Pb-Zn category. Whereas, the ore-forming fluids and sulfur of Au mineralization were of the Mesozoic magmatic origin, with the lead materials from the Paleoproterozoic Zhenzhumen Formation. These features demonstrate that the Au minerlization was closely related to the Mesozoic magmatic-hydrothermal activity and thus categorized as Mesozoic magmatic hydrothermal Au.