西藏墨竹工卡县甲马多金属矿床几组年龄数据的比较与成因研究  

Comparation of several sets of age data and the origin of the Jiama polymetallic ore deposit in Mozugongka County,Tibet.

作　　者：李胜荣[1] 袁万明[1] 屈文俊[2] 邓军[1] 侯增谦[3] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]国家地质实验测试中心,北京100037 [3]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2008年第3期511-518,共8页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2002CB412603);国家自然科学基金项目(40073012);中国地质调查局地质大调查项目(200313000068)资助

摘　　要：甲马矿床是西藏腹地冈底斯带已投入开采的大型多金属矿床,有关其成因的研究直接影响着该带多金属矿床的区域找矿方向及时冈底斯带地球动力学过程的成矿效应研究。目前对该矿床成因尚无统一的认识,关键在于未获得成矿年龄的可靠结果。本文比较了前人和本文获得的 Rb-Sr(260Ma 和54Ma)、裂变径迹(>25～22Ma)和 Re-Os(模式年龄15.4～15.5Ma,等时线年龄15.18Ma 和模式年龄15.23～15.62Ma,等时线年龄15.41Ma)等年龄数据,认为 Re-Os 同位素年龄数据最为可靠,应作为矿床的成矿年龄。矿床 Re-Os 同位素年龄与矿区外围花岗闪长斑岩全岩 K-Ar 同位素年龄一致,显示甲马夕卡岩及其中的多金属矿床为斑岩-多底沟组灰岩接触带岩浆热液交代-充填成因,该矿床属冈底斯中段的后碰撞岩浆热液成矿系统。预计该区深部及外围存在斑岩型矽卡岩型-脉型含金多金属矿化。The Jiama ore deposit is a large scaled polymetallic deposit being mined in the Gongdese metallogenic belt of the central Tibet. The ore is hosted by garnet-diopside-tremolite skarn without spatial contact to igneous rocks. The origin of the deposit is a key factor affecting the regional prospecting of polymetallic ore deposits in the belt, and it＇s also essential to the study of mineralization effect of the geodynamic evolution of the belt, Until now there are still no commonly accepted opinion with regard the origin of the deposit mainly because of lack of reliable chronological data. The authors compared the Rb-Sr age data （260Ma and 54Ma） , apatite fission track age data （ 〉 25 - 22Ma） and Re-Os age data （ model age 15.4 - 15.5Ma, isochrone age 15. 18Ma and model age 15.23 15.62Ma, isochrone age 15.41Ma） , and suggest that the Re-Os data are more reliable and should be taken as the mineralization age. The Re-Os data are consistent with the whole rock K-At isotopic age of the granodioritic porphyry in the periphery of the mine, showing that the skarn and metallogenic ore are of magmatic hydrothermal alteration-filling origin located nearby the spatial boundary between a kind of Himalayan period porphyry and the limestone of the Jurassic Duodigou Formation, and the ore deposit is belong to the postcollision magmatic hydrothermal metallogenic system. The authors predict that exist a series of porphyry type-skarn type-vein type poly-metallic mineralization ores there are in the depth and the periphery of the mine.

关 键 词：RB-SR RE-OS 裂变径迹 多金属矿床 甲马 西藏 

分 类 号：P597.3[天文地球—地球化学] P611.13[天文地球—地质学]