新疆萨尔朔克铜金多金属矿床成矿围岩锆石年龄、Hf同位素及其成矿背景  

Zircon U-Pb age and Hf isotope compositions of the wall rocks in the Sarshuoke gold-copper polymetallic deposit in Altay,Xinjiang: Implications for the ore-forming conditions

作　　者：沈雪华[1] 姚春彦[1] 樊献科 叶现韬[1,2] 董永观[1] 

机构地区：[1]中国地质调查局南京地质调查中心,江苏南京210016 [2]中国地质科学院,北京100037

出　　处：《地质通报》2016年第1期167-174,共8页Geological Bulletin of China

基　　金：国家305项目(编号:2011BAB06B03-01)

摘　　要：新疆萨尔朔克金铜多金属矿床产于中泥盆统阿舍勒组上亚组的中酸性火山岩-次火山岩中,地表以金（铜）矿化为主,矿体形态及空间分布严格受NNW向断裂破碎带控制,矿体呈脉状、透镜状。金（铜）矿石以蚀变岩型为主,其次为石英脉型,赋矿围岩为黄铁绢英岩化流纹斑岩。金主要赋存在微细粒黄铁矿等硫化物和脉石英中,黄铜矿常呈不规则细脉状出现。在地表100m以下,出现铅锌矿化,且向深部铅锌品位较高,一般3%~5%,最高达12%以上。流纹斑岩与金铜多金属矿关系密切。通过锆石U-Pb同位素测年和Hf同位素测试分析,获得流纹斑岩的成岩年龄为386.2±1.5Ma,εHf（t）在7~13之间,主要集中在8.5~12.5之间。上述结果表明,流纹斑岩可能形成于早泥盆世晚期活动大陆边缘环境,是俯冲增生的产物。铅锌矿化是386Ma流纹斑岩期后岩浆作用的产物,而金铜矿化则是在含矿流纹斑岩的基础上,经其后火山热液叠加作用发生的。The Sarshuoke gold-copper polymetallic deposit is hosted in the intermediate andestic-acidic volcanic-subvolcanic rocks of the Devonian Ashele Formation. Gold-copper （Au-Cu） mineralization mainly occurs at the shallow level （less than 100m in depth）, and the shapes of veins and lenticnlar Au-Cu orebodies are significantly constrained by the NNW-trending faults. Au-Cu minerals exist mainly in hydrothermal altered rocks with some in the quartz veins, and the wall rocks are the pyritization-phylliciza- tion rhyolite porphyry. Gold mainly occurs in fine-grained pyrite and other sulfides and quartz. The lead-zinc （Pb-Zn） ores are mainly distributed at lower level at ca.100m under the surface. The grade of Pb-Zn increases with the increasing depth. The grade of Pb-Zn ranges from 3% to 5%, and the highest grade could reach up to 12%. Au-Cu polymetallic mineralization is related closely to rhyolite porphyry. Zircon U-Pb dating shows that the wall rock of the deposit, i.e., rhyolite porphyry, crystallized at 386.2 ± 1.5Ma. Zircon Lu-Hfisotope analysis yielded pronounced depleted Hfisotope composition with εHf（t） ranging from 7 to 13, mostly 9-10. The data obtained by the authors, in combination with regional geology and previous studies, reveal that the rhyolite porphyry was formed on an active continental margin related to plate subduction in late Early Devonian. Pb-Zn mineralization is genetically related to the rhyolite porphyry igneous activity. Furthermore, Au-Cu mineralization most possibly took place at the late stage and was ge- netically related to volcanic hydrothermal effects on the basis of Au-Cu-bearing rhyolite porphyry.

关 键 词：金铜多金属矿床 U-PB年龄 锆石Lu-Hf同位素 成矿背景 萨尔朔克 新疆 

分 类 号：P534.44[天文地球—古生物学与地层学] P597.3[天文地球—地质学]