Sulfur, Carbon and Lead Isotope Studies of the Dajing Polymetallic Deposit in Linxi County, Inner Mongolia, China - Implication for Metallogenic Elements from Hypomagmatic Source

摘要

The Dajing Cu-polymetallic ore deposit in Linxi county, Inner Mongolia Autonomous Region, China, is economically a valuable Co-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~34S values range from -1.8 to +3.8 per thousand +0.65 per thousand distributions of the delta~34S values with approx +1 per thousand peak value, including the published data, and the delta ~13C values around -5 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 ~206Pb/~204Pb, ~207Pb/~204Pb and ~208Pb/~204Pb ratios of sulfide ores range respectively within l8.257 approx l8.368, l5.476 approx l5.609, and 37.9l6 approx 38.355 with the model ages of l22 approx 209 Ma. The black shale, however, contains higher radiogenic lead with the ~206Pb/~204Pb ratios of 18.473 approx 20.156, differing from the ores. However, the ~206Pb~204Pb, ~207Pb/~204Pb and ~208Pb/~204Pb ratios of the ore, basaltic porphyrite and feldspar leads are similar, and lie on the same lines in the diagrams of ~208Pb/~204Pb vs. ~206Pb~204Pb and ~207Pb/~204Pb vs. ~206Pb/~204Pb. 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.