摘要
照壁山金矿床是北山地区中部金矿集中区最具代表性的金矿床之一 ,金矿化主要在黑云母花岗岩株内或沿其与志留系公婆泉群火山—沉积岩的接触带产出 ,黑云母4 0 Ar 3 9Ar同位素年龄为 2 96± 5Ma。金矿体主要由含金石英脉 ,网脉和细脉浸染状块体组成 ,金属矿物主要有黄铁矿、方铅矿、闪锌矿、黄铜矿、自然金和银金矿 ,脉石矿物为石英和绢云母。围岩蚀变自含金矿脉 (体 )向外 ,分别为硅化、绢云母化和绿泥石化 ;另外 ,沿岩体与火山—沉积岩接触带常可观察到黄铁绢英岩化。微量元素和硫、氧、氢及铅同位素数据表明 :黑云母花岗岩是同碰撞造山期深源岩浆与地壳物质相互作用的结果 ,成 (岩 )矿物质主要来自壳幔混合源 ,含矿热液是岩浆热流体与大气降水混合的产物。海西期花岗质岩浆活动不仅为金矿床的形成提供了物质和热力来源 ,而且是成矿热液对流循环的“发动机” ,成矿体系温、压降低是导致金沉淀与富集的重要控制因素。
The Zhaobishan gold deposit, as one of the most important gold deposits in northwest China, is located at the convergence area of the Siberian, Kazakhstanian and Tarim paleoplates. The gold mineralization occurred within the Zhaobishan biotite granitoid stock as quartz vein and veinlet group. The systematic field investigations showed that the gold mineralization was spatially and temporally related to the Hercynian granitoid magmatism. The oxygen and hydrogen isotopic analyses on quartz separates from the gold bearing quartz veins and the granitoid revealed that the ore fluid for the deposit was mainly derived from a mixed source of Hercynian igneous fluid and Paleozoic meteoric water. The lead isotope data on pyrite, chalcopyrite and gold ore samples from the Zhaobishan area constituted a mixing line cutting the Pb growth curves of upper crust, orogen, lower crust and mantle. Two chalcopyrite, one pyrite and two gold ore samples from the gold bearing quartz veins fell between the areas of the Hercynian biotite granite samples. The result of lead isotope analyses indicated the Hercynian granitoid being initial lead source for the gold bearing quartz veins. Both geological evidences and isotope data demonstrated that the lead, gold and other metal elements of the gold bearing vein system mainly came from the Hercynian granitoids which was probably derived from the re melting of previously formed supracrustal rocks during Paleozoic orogeny. Meanwhile, the genetic model and mineral exploration criteria of the Zhaobishan gold deposit could also be used during the comprehensive evaluation of the concealed gold deposits in the Beishan region.
出处
《地质科学》
CAS
CSCD
北大核心
2002年第2期207-218,共12页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金项目 (编号 :4 0 0 730 1 5 )
国家地质调查项目 (编号 :K1 3 32 )
