Sulfur, carbon and lead isotope studies of the Dajing polymetallic deposit in Linxi County, Inner Mongolia, China - Implication for metallogenic elements from hypomagmatic source

The Dujing Cu-polymetallic ore deposit in Linxi county, Inner Mongolia Autonomous Region, China, is economically a valuable Cu-Sn-Ag-Zn-Pb deposit in the southern section of the Da Hinggan metallogenic province. For the analyzed 23 samples of sulfide minerals, including chalcopyrite, pyrite, sphalerite and galena, the delta(34)S values range from -1.8 to +3.8 parts per thousand with an average of +0.65parts per thousand. The narrow distributions of the delta(34)S values with similar to+1parts per thousand peak value, including the published data, and the delta(13)C values around -5parts per thousand indicate that the sulfur and carbon of the hydrothermal fluids are derived from a hypomagmatic source, and exclude the possibility that the hosted strata, i.e., the Upper Permian Linxi Formation, provided certain amounts of sulfur and carbon. The Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 ratios of sulfide ores range respectively within 18.257similar to18.368, 15.476similar to15.609, and 37.916similar to38.355 with the model ages of 122similar to209 Ma. The black shale, however, contains higher radiogenic lead with the Pb-206/Pb-204 ratios of 18.473similar to20.156, differing from the ores. However, the Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 ratios of the ore, basaltic porphyrite and feldspar leads are similar, and lie on the Same lines in the diagrams of Pb-208/Pb-204 vs. Pb-206/Pb-204 and Pb-207/Pb-204 vs. Pb-206/Pb-204. The fact that these mixing lines are composed of the two end members, the mantle and orogenic belt, strongly supports that all the metallogenic elements were carried by the hypomagma mixing the matters of the mantle and orogenic belt prior to the Mesozoic. Therefore, the Dajing ore deposit is a typical magmatic-hydrothermal vein type ore deposit associated with subvolcanic rocks.