A Study On The Characteristics And Genesis Of Pb-Zn(Au) Polymetallic Deposits, Dongzhi, Anhui

The Zhaojikou Pb-Zn deposit is a medium-sized deposit discovered currentlyin southern Anhui province and fewer attention has been paid to this region. Basedon the general knowledge of the regional geology, the field investigation of1:10000geological mapping, cross-sections measurement and drill-core samplesobservation have been carried out in this paper, as well as petrography to obtaingeological characteristics of Zhaojikou Pb-Zn deposit and Xucun gold deposit.Furmore, ore-forming fluid inclusions and stable isotopic geochemistry of thePb-Zn deposit and ore-forming elements of the related stratum and rocks were alsosystematically investigated in Zhaojikou region. The main results are as follows:Zhaojikou Pb-Zn deposit is located in Huansha Formation of Jixian System inthe the Mesoproterozoic. The occurrence of ore-body controlled by regionalstructures is vein and stockwork. The ore mineral assemblage is comparativelysimple with galena and sphalerite, with fewer chalcopyrite and pyrite. The gangueminerals include quartz, calcite and fewer siderite. The ore is characterized by vein,stockwork and massive structure, filling texture, inclusion texture and droplet-liketexture. The Xucun gold deposit consists of Dongkengwu, Fangkengwu andGaohuatang deposits. The ore-body primarily exists in Xiuning Formation of SinianSystem, Xiaoanli and Dengjia Formation of Qingbaikou System. They arecontrolled by unconformity surfaces and structural fracture belts with the mainlymineralized type of quartz vein type. The primary ore mineralis gold, pyrite withfewer galena, sphalerite and chalcopyrite, and quartz is the gangue mineral. The orehas massive structure, breccias structure and disseminated structure, finecrystallized texture.The ore-controlling structure and depositing ore structure of Zhaojikou Pb-Zndeposit is Zhaojikou overturned fold, Dongzhi fault and westward secondary fault.The argillaceous sedimentary induced by fault activities in Dongzhi fault has animportant effect on the ore formation.The ore-forming elements characteristics of the related stratum and rocks,carbon-oxygen isotope and sulfur isotope features of deposit all indicated that mostof the ore-forming matters were main from deep magma with a minor of stratum inorigin. The geochemical characteristics of ore-forming fluid inclusions andhydrogen-oxygen isotopic geochemisty show that the ore-forming fluid was charactered by low-temperature and medium-low salinity which was a mixture ofmagmatic water and meteoric water in origin. Evidneces from the mentioned asabove, it can be proposed that Zhaojikou Pb-Zn deposit is an epithermal Pb-Zndeposit related to late Yanshanian magma activity.