Structure, Alteration, and Fluid Inclusion Study on Deep and Surrounding Area of the Dongping Gold Deposit, Northern Hebei Province, China

详细信息   

• 责任者：Zhang Guorui (Resource Engineering Department ; University of Science and Technology Beijing ; Beijing 100083 ; China) ; Xu Jiuhua
• 刊名：Acta Petrologica Sinica
• 出版年：2012
• 卷期：28(2)
• 关键词：金矿 ; gold ores ; 河北 ; Hebei Province
• 页码：p.637-661
• 图表：12 illus., 2 tables, 28 refs.
• 分类号：1001
• issnNo：ISSN1000-0569
• isbnNo：CN11-1922/P

摘要

 The gold deposits in Dongping area,northern Hebei Province are firstly found among the alkaline complex in China.These gold deposits are often recognized as alkaline rock-related gold deposits because of surrounding rocks.In recent years,it is indicated that the alkaline complex formed in the Hercynian,but gold mineralization occurred in the Yanshanian stage through geochronology.These gold deposits are strictly controlled by the structure fractures and have a significant mineralization of structure-alteration-fluids.Alterations and mineralization of the Dongping gold deposit can be divided into four stages.They are(I) feldspar-quartz veins stage,(II) pyrite-white quartz stage,(III) sulphides-smoky gray quartz vein stage,and(IV) late carbonate stage.Zonation is clear in altered fractured ore-controlling rocks.There are five zones from unaltered syenite of footwall to centre of ore body:zone 0-the original rocks(monzonite,syenite) zone;zone I-microclinization zone;II-silicified sericited microclinite zone;III-fractured microclinite zone;and IV-fault gouge zone.From zone 0 to zone III,the content of Au increases,correspondingly,Ag,Cu,Pb,Zn,Mo also increase slightly.A study of fluid inclusion shows that CO₂-rich inclusions both exist in the stage I and the stages II,III.Ore-forming fluids belong to H₂O-CO₂-NaCl hydrothermal systems with medium-high temperatures and low saltinities.CO₂-rich inclusions gradually decrease from ductile to brittle transformation in ore-bearing tectonic zones.The homogenization temperatures of L-V,H₂O-CO₂ inclusions are 220.3～359℃,346.5～383.5℃in feldspar quartz veins of stage I,and the salinity of L-V inclusions is 1.1%～3.1% NaCleqv;the homogenization temperatures of L-V,H₂O-CO₂ inclusions are 217.2～372.5℃,241.2～396.7℃ in pyrite-white quartz veins of stage II,and the salinity is 1.1%～5.7% NaCleqv,2.2%～6.2% NaCleqv respectively;the homogenization temperatures of L-V,H₂O-CO₂ inclusions are 158.2～350.5℃,215.2～378℃ in smoky gray quartz veins of stage III,and the salinity is 0.7%～5.5% NaCleqv,3.0%～6.0% NaCleqv respectively;and those of L-V inclusions are 151.2～249.8℃ in the late quartz veins of stage IV,and the salinity is 0.9%～8.3% NaCleqv.In its surrounding area,Zhuanzhilian mine,the homogenization temperatures of fluid inclusions in white quartz vein(II) are 220～416.2℃,and those in dark grey quartz vein(III) are 195.3～425℃.Gold-rich quartz veins were formed in hypothermal fluids(T>300℃,up to higher than 400℃) and deep portion(pressures higher than 70～160MPa) .It is more resonable to consider the gold deposit in the Dongping area as intrusion-related gold deposits,based on geological setting,hydrothermal alteration,ore mineral assemblage,and characteristics of fluid inclusions.