Geologic Feature And Discussion On Genesis Of The Dongping Gold Deposit,Northern Hebei Province

Dongping Gold Deposit is located in the Chongli County,Hebei Province,Which is located at the middle part of North edge of North China Craton,in the south of the Xuanhua-Chongli-Chicheng Deep Fault,and belongs to the Zhang-Xuan polymetallic mine area in Northern Hebei.It is the first gold found in alkaline rocks in China.The scale of the current deposit has reached a large scale.In this paper,through careful observation and systematic sampling of the field,downhole and boreholes of the Dongping Gold Mine,combined with studies of petrology,fluid inclusions and isotope geochemistry in the interior,discuss the sources of ore-forming fluids and ore-forming materials.Combined with regional mineralization geological background,the cause of the deposit was analyzed and a metallogenic model was established.The research achieved the following main results and understanding:1.The Dongping gold deposit is hosted in the Shuiquangou alkaline complex.Its north-south boundary is controlled by the Yangmuwa-Mazhangzi-Jinjiazhuang fault and the Zhongshangou-Honghuabei-Shangshuiquan fault,respectively.Ore body is controlled by the NNE directional and NW conjugate fault structures,most of them are distributed in vein-shaped geese.The ore types are dominated by quartz veins and potassium-siliconation altered rocks.2.According to the interpenetration relationship between ore veins,ore structure and mineral symbiotic combination,combined with previous research results,the Dongping gold mineralization process is divided into four metallogenic stages:potassium silicification stage,milky quartz-yellow Iron ore stage,soot grey quartz-polymetallic sulphide stage and quartz-carbonate stage.3.The fluid inclusions in the Dongping gold deposit can be divided into three types:gas-liquid two-phase inclusions,CO₂-rich three-phase inclusions,and containing crystal inclusions.The temperature of the inclusions was found to be between 220°C and 300°C.The salinity was between 3.5 and 9.4%NaCl eq and the density was between 0.47 and 1.05 g.cm^-3.The ore-forming fluids were mainly medium-temperature and low-salt but it contains crystal inclusions and CO₂-rich inclusions,indicating that its magmatic hydrothermal fluid is involved in ore formation.4.By comparing the H-O isotopes of the Dongping gold deposit,it was found that the fluid source is mainly a mixture of atmospheric water and magmatic water.For the analysis of S and Pb isotopes,they all indicated the involvement of the deep-sourced materials.The source of the material should be the source of upper crust melting and upwelling of mantle materials.5.Summarize and analyze the metallogenic geological characteristics of Dongping gold deposit and analysis of metallogenic geochemistry data,compare it with different characteristics of regional ore deposits and typical deposits,and finally conclude that Dongping gold deposit is a post-magmatic hydrothermal fluid Mineral deposits.