GUN Min-shan1,2，LV Xin-biao2,3*，ZENG Dao-guo1，LI Jie2，CHEN Chao3，LI Jian-yang2，WANG Hua-jian2
(1. Institute of Geological and Mineral Exploration, Non-Ferrous Metals and Nuclear Industry Geological Exploration Bureau of Guizhou, Guiyang 550005, China;
2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;
3. Institute of Geological Survey, China University of Geosciences, Wuhan 430074, China)
Abstract: The Erdahe deposit is a large skarn type Pb-Zn-Ag polymetallic deposit discovered in the northern-central part of the Greater Khingan Mountains in recent years. The mineralization of the deposit had undergone five evolution stages including the early skarn, late skarn, pyrrhotite-pyrite-quartz, quartz polymetallic sulfides, and quartz-carbonate stages. In order to discuss the source of metallogenic materials, S and Pb isotopes of the main metal sulfides, granite-porphyry, diorite, and Mesozoic volcanic rocks in the deposit have been analyzed in this paper. The results show that the δ34S values of major metal minerals in the deposit are ranged from 5.8‰ to 8.9‰, with a tower shaped histogram. They are similar to the sulfur isotopic compositions of the typical skarn type lead-zinc deposits and the regional typical lead-zinc deposits, and are relatively similar to those of granotoids, indicating that the sulfur of the deposit could be mainly derived from the deep-seated magmatic-hydrothermal system. The sulfur isotope exchange occurred between the Ordovician marine strata and the evolved hydrothermal fluid. The sulfur isotopic compositions of sulfides of main-ore stage of the deposit are subsequently changed in order of δ34Spy＞δ34SSp＞δ34SCcp＞δ34SGn, indicating that the balance of sulfur isotopic fractionation has been reached in the main-ore stage of the deposit, with the calculated equilibrium temperatures of those co-existed mineral pairs of227－382 ℃. Lead isotopic compositions show that the lead of ore minerals was characterized with highly radioactive crustal lead, while the lead of granitic porphyry, diorite, and Mesozoic volcanic rocks was characterized with low radioactive lead. The lead isotopic data are all plotted in the vicinity of the evolution line of orogenic belt in the tectonic discrimination diagram with obvious linear distribution characteristics, indicating that they have the same lead source and lead isotope evolution characteristics. The lead data are all plotted into the lead source area of the mixed subduction zone, related to magmatism, of the upper crust and mantle in the Δγ-Δβ diagram. In summary, the ore-forming materials were sourced from the contribution of multiple components. However, the isotopic compositions, μ values, and Th/U ratios of ore minerals are respectively similar to those of granite-porphyry and diorite, indicating that the main ore-forming materials could be mainly sourced from magma of the Yanshanian medium- acidic intrusive rocks, combined with the occurrence of ore bodies mainly in the contact zones between intrusive bodies (granite porphyry and diorite) and carbonates.
Keywords: S, Pb isotopes; the northern-central part of the Greater Khingan Mountains; lead-zinc deposit; Ore-forming materials
ACTA MINERALOGICA SINICA Vol. 41, No.2, 2021, page 150-162
