Rb-Sr Dating of Sphalerites from Shizishan Pb-Zn Deposit in Huayuan Ore Concentration Area,Western Hunan, and Its Geological Significance
Duan Qifa
Cao Liang
Zeng Jiankang
Zhou Yun
Tang Zhaoyang
Li Kun
Abstract：The Huayuan ore concentration area in the western Hunan Province,located in transitional zone between the south-eastern margin of Yangtze block and the Xuefeng (Jiangnan)orogenic belt,is important section of the Xiangxi-Exi metalloge-netic belt,and is the only one which occurs in limestone of Lower Cambrian strata in the Yangtze block.The Shizishan Pb-Zn deposit which was one of recently discovered Pb-Zn deposits in Xiangxi-Exi metallogenetic belt is located in the center of the Huayuan ore concentration area,and its main ore bodies occur in stratoid with the same trending as the strata and are sharply bounded by wall rocks with weak hydrothermal alteration such as calcitization.Ore bodies are strictly controlled by algal lime-stone of the third section of the lower member of the Lower Cambrian Qingxudong Formation.Ore minerals are mainly sphal-erite,and a small amount of galena and pyrite,whereas gangue mineral is mainly calcite,and a small amount of barite and flu-orite.Using the total-sample-dissolution method and leaching method to sphalerite in the Shizishan Pb-Zn deposit for Rb-Sr iso-chron dating.The isochron ages are obtained 410±12 Ma (MSWD=2.20)with initial 87 Sr/86 Sr value of 0.709 1 6 for mineral-phase+residue phase,which shows that the Early Devonian is the main time for the formation of the Shizishan Pb-Zn deposit. Research results indicate that the formation of the deposit is probably related to the regional migration of the basin fluid when the crust is stretched behind the Late Caledonian tectonic movement in Early Devonian,and the age is also a constraint on the Pb-Zn ore-forming time of the whole Huayuan ore concentration area.The initial 87 Sr/86 Sr value of the mineral phase+residue phase is 0.709 1 6,which is slightly higher than those of the ore-bearing limestone,and close to those of the overlying dolostone of Middle-Upper Cambrian strata,indicating that the ore-forming materials of the ore bodies in the Shizishan Pb-Zn deposit are possibly derived from the overlying dolostone strata.It is thus concluded that direct dating of the ages of metal minerals by u-sing Rb-Sr isochron method for single minerals and mineral residues could serve as a routine dating method.
Keywords：sedimentologyinclusionssphalerite Rb-Sr isotopic datingisochron agemineralization epochShizishan Pb-Zn depositHuayuan ore concentration areaore deposit
Publication Date：2014-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：11( 977-986,999 )