Carbon, hydrogen and oxygen isotopes of the Huayuan Pb-Zn ore deposit in western Hu'nan Province and their implications for the source of ore-forming fluid

With more than ten million tons of lead and zinc resource reserves, the Huayuan lead-zinc deposit is expected to become the largest Pb-Zn deposit in China and one of the world-class superlarge ore deposits.In this paper, researches on carbon, hydrogen, oxygen isotope of calcite and sphalerite from the Huayuan lead-zinc deposit formed during the main mineralization period are report-ed.The analytical results show that δ¹³C_PDB values of calcite samples display the range from 2.71‰ to 1.21‰, the δ¹⁸O_SMOW values are in the range from 16.09‰ to 22.48‰.The δ¹³C_PDB and δ¹⁸O_SMOW isotope values of calcite minerals from the Tuanjie, Limei, Tu-diping, Fengtang and Dashigou lead-zinc deposits are gradually reduced in turn, falling between native carbonate rock and marine carbonate in the δ¹⁸O_SMOW-δ¹³C_PDB diagram.In the Huayuan lead-zinc deposit, the carbon in the ore-forming fluid was mainly de-rived from marine carbonate dissolution.The δ¹³C_PDB values of surrounding rocks in the Huayuan lead-zinc deposit vary from 0.15‰ to 1.17‰, the δ¹⁸O_SMOW values vary from 19.79‰ to 23.89‰, and the surrounding rock is sedimentary marine carbonate.The δD_SMOW values of fluid in calcite and sphalerite vary from 91.1‰ to 15‰, the δ¹⁸O fluid vary from-4.1‰ to 9.25‰, and the migra-tion direction of fluid in the ore district was from north to south.The δ¹⁸O_fluid-δD_SMOW diagram shows that the main source of oreforming fluid was formation water and atmospheric precipitation.Water-rock reaction between ore-forming fluid and wall rock was the main mechanism leading to the precipitation and crystallization of calcite and sphalerite in the Huayuan Pb-Zn deposit of western Hu'nan Province.