Sources Of Ore-forming Metals,Metalligenic Age And Geodynamic Background Of The Tonggou Gold Deposit,Xiaoqinling Goldfield

Situated in the southern margin of the North China Craton,the Xiaoqinling goldfield is the second largest gold producer in China,which can be roughly divided into the north,the middle,and the south ore belts.A large number of previous studies mainly focused on the south and north ore belts,but relatively few on the middle ore belt,which affected the comprehensive understanding of the characteristics,mechanism and law of gold mineralization in Xiaoqinling gold field as a whole.In this paper,the Tonggou gold deposit in the middle ore belt,which is less studied,is taken as the research object,and systematic geological,trace element,isotope geochemistry and geochronology of the deposit are carried out,and the main conclusions are summarized as the follows:1.The mineralization process of Tonggou gold deposit in Xiaoqinling can be divided into four stages from early to late:(?)pyrite-quartz stage,(?)natural gold-quartz-pyrite stage,(?)natural gold-quartz-polymetallic sulfides stage and (?)quartz-carbonate stage,and stage ? and stage ? are the main mineralization stages.Additionally,tellurides associated with gold,such as tellurobismuthite and altaite,are also well developed.2.LA-ICP-MS trace element composition characteristics of pyrite in-situ micro area show that pyrite in Tonggou gold deposit is poor in as,while in pyrite of stage ? and stage ?,there is a significant positive correlation between Au and Ag,Te,Bi,indicating that Au mainly occurs as submicroscopic inclusions of Au-Ag-Te-Bi assemblages in the pyrite.Au,Te and Bi migrate,enrich and precipitate together in the form of melt.The Au(Ag)-Te-Bi enrichment in Tonggou gold deposit and Xiaoqinling gold field indicates that the ore-forming metals are related to deep magmatism.3.The in-situ S isotopic compositions of sulfides in different mineralization stages are significantly different from those of pyrites in the wall rocks of Taihua Group,indicating magmatic sulfur source.The in-situ Pb isotopic composition of galena indicates a mixed Pb source with a certain proportion of mantle derived components.S-Pb isotope analysis shows that the ore-forming metals of Tonggou gold deposit are derived from mantle derived magmatic hydrothermal activity.4.The U-Pb age of the hydrothermal monazite associated with gold-bearing pyrite is 128±16 Ma.The large-scale mineralization of the Xiaoqinling goldfield,including the Tonggou gold deposit,was formed in regional extensional tectonic system in eastern China in early Cretaceous,which was the product of mantle derived magmatic hydrothermal activity in the process of large-scale lithospheric thinning.