柴北缘双口山金- 银- 铅矿床赋矿围岩及含金石英脉热液锆石U- Pb定年对成矿时代的限定及其成因启示

双口山金- 银- 铅矿床地处柴北缘西段，赋存在滩间山变基性- 超基性变火山岩中。矿体由金矿体和银铅矿体组成，成矿作用与热液活动密切相关。本文通过对双口山含金矿体赋矿围岩及含金石英脉进行LA- ICP- MS锆石U- Pb年代学分析和研究。结果表明，赋矿围岩形成时代为443±2. 9Ma，与区域滩间山群火山岩形成年代一致(440~490Ma)。含金石英脉热液锆石U- Pb年代为402. 8±4. 2Ma，与区域金矿床成矿年龄以及韧性剪切带年龄相接近(~400Ma)，代表了金矿体热液作用及成矿时代。结合地质特征及前人研究，表明双口山金银铅矿床是柴北缘造山带在不同造山带演化阶段，由不同成矿作用，在不同时期，相互叠加形成的复合型多金属矿床。金矿体具有典型造山型金矿床特征的变质热液型金矿，其成因主要与造山运动过程中的变质和变形作用有关, 成矿物质和流体来源于绿片岩相的滩间山群变基性- 超基性变火山岩。银铅矿体为岩浆热液型，成矿与后碰撞造山作用伸展- 构造转换有关的岩浆作用有关，成矿物质和流体来源于晚泥盆世深部含矿岩浆作用。

LA- ICP- MS zircon U- Pb age of the host rock and hydrothermal zircon in gold- bearing quartz vein of Shuangkoushan Au- Ag- Pb deposit, North Qaidam:limitation for the mineralization age and implication for the genesis of the deposit

The Shuangkoushan gold- silver- lead deposit is located in the western part of the North Qaidam, which is hosted in metamorphic basic- ultrabasic volcanic rocks of Tanjianshan Group. The deposit were composed of gold ore body and silver- lead ore body, and the mineralization is closely related to hydrothermal activity. In this study, we reported the age of the host rock and gold- bearing quartz veins in the gold- bearing ore body through the LA- ICP- MS zircon U- Pb geochronology analysis. It indicates that the formation age of host rock is 443±2. 9 Ma, which is consistent with theVolcanic rocks of Tanjianshan group with an age range from 440 Ma to 490 Ma. The hydrothermal zircon U- Pb age of gold- bearing quartz vein is 402. 8±4. 2 Ma, which is close to the metallogenic age of gold deposits and ductile shear zone (~400 Ma) in local area, representing the hydrothermal action and mineralization age of the Shuangkoushan gold ore body. Together with the geological characters and previous researches, indicate that the gold ore body and silver- lead ore body are the products of different mineralization stage associated with different orogenic processes. The gold ore body can be classified as metamorphic- hydrothermal type and is genetically associated with orogenic metamorphism and deformation during the North Qaidam orogeny, with the gold and ore- forming fluids being sourced from greenschist facies metamorphic basic- ultrabasic volcanic rocks. The silver- lead ore body can be classified as intrusion- related magmatic- hydrothermal type and is genetically associated with magmatic activity at extensional faults in the post- orogeny period, with the silver, lead and ore- forming fluids being sourced from deep magmatism in late Devonian.