Zhou Jiaxi

Isotopic Compositions of Sulfur in the Jinshachang Lead-Zinc Deposit Yunnan, China, and its Implication on the Formation of Sulfur-Bearing Minerals

: The Jinshachang lead–zinc deposit is mainly hosted in the Upper Neoproterozoic carbonate rocks of the Dengying Group and located in the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn–Ag multi-metal mineralization area in China. Sulfides minerals including sphalerite, galena and pyrite postdate or coprecipitate with gangue mainly consisting of fluorite, quartz, and barite, making this deposit distinct from most lead-zinc deposits in the SYG. This deposit is controlled by tectonic structures, and most mineralization is located along or near faults zones. Emeishan basalts near the ore district might have contributed to the formation of orebodies. The δ34S values of sphalerite, galena, pyrite and barite were estimated to be 3.6‰–13.4‰, 3.7‰–9.0‰, −6.4‰ to 29.2‰ and 32.1‰–34.7‰, respectively. In view of the similar δ34S values of barite and sulfates being from the Cambrian strata, the sulfur of barite was likely derived from the Cambrian strata. The homogenization temperatures (T≈ 134–383°C) of fluid inclusions were not suitable for reducing bacteria, therefore, the bacterial sulfate reduction could not have been an efficient path to generate reduced sulfur in this district. Although thermochemical sulfate reduction process had contributed to the production of reduced sulfur, it was not the main mechanism. Considering other aspects, it can be suggested that sulfur of sulfides should have been derived from magmatic activities. The δ34S values of sphalerite were found to be higher than those of coexisting galena. The equilibrium temperatures calculated by using the sulfur isotopic composition of mineral pairs matched well with the homogenization temperature of fluid inclusions, suggesting that the sulfur isotopic composition in ore-forming fluids had reached a partial equilibrium.

H‐O‐S‐Cu‐Pb Isotopic Constraints on the Origin of the Nage Cu‐Pb Deposit, Southeast Guizhou Province, SW China

: The Nage Cu-Pb deposit, a new found ore deposit in the southeast Guizhou province, southwest China, is located on the southwestern margin of the Jiangnan Orogenic Belt. Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations, and are structurally controlled by EW-trending fault. It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb. Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks. The ore minerals include chalcopyrite, galena and pyrite, and gangue minerals are quartz, sericite and chlorite. The H-O isotopic compositions of quartz, S-Cu-Pb isotopic compositions of sulfide minerals, Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit. The δCuNBS values of chalcopyrite range from −0.09% to +0.33‰, similar to basic igneous rocks and chalcopyrite from magmatic deposits. δ65CuNBS values of chalcopyrite from the early, middle and final mineralization stages show an increasing trend due to 63Cu prior migrated in gas phase when fluids exsolution from magma. δ34SCDT values of sulfide minerals range from −2.7‰ to +2.8‰, similar to mantle-derived sulfur (0±3‰). The positive correlation between δCuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma. δDH2O-SMOW and δ18OH2O-SMOV values of water in fluid inclusions of quartz range from −60.7‰ to −44.4‰ and +7.9‰ to +9.0‰ (T=260°C), respectively and fall in the field for magmatic and metamorphic waters, implicating that mixed sources for H2O in hydrothermal fluids. Ores and sulfide minerals have a small range of Pb isotopic compositions (208Pb/204Pb=38.152 to 38.384, 207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve, and similar to Neoproterozoic host rocks (208Pb/204Pb=38.201 to 38.6373, 207Pb/204Pb=15.648 to 15.673 and 206Pb/204Pb=17.820 to 18.258), but higher than diabase (208Pb/204Pb=37.830 to 38.012, 207Pb/204Pb=15.620 to 15.635 and 206Pb/204Pb=17.808 to 17.902). These results imply that the Pb metal originated mainly from host rocks. The H-O-S-Cu-Pb isotopes tegather with geology, indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type.

Research Progress of the Mineralization of Carbonate-Hosted Pb-Zn Deposits in the Sichuan-Yunnan-Guizhou Pb-Zn Metallogenic Province, Southwest China

The Sichuan-Yunnan-Guizhou(SYG)Pb-Zn metallogenic province in the western Yangtze Block,is a key component of the low-temperature metallogenic domain in South China.In this area,more than 400 Pb-Zn deposits have been discovered,and the total proven reserves are up to 260 million tons with lead and zinc grade reaching 10%,even up to 30%.Another important