西藏蒙亚啊铅锌矿床矽卡岩型矿体白云母Ar-Ar年代学研究及其地球动力学意义  

Ar-Ar Age of Muscovite from Skarn Orebody of the Mengya'a Lead-Zinc Deposit in Tibet and Its Geodynamic Significance

作　　者：付强[1,2] 黄克贤[3] 郑远川[4] 杨竹森[5] 段连峰[4] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]中国地质矿业总公司,北京100029 [4]中国地质大学地球科学与资源学院,北京100083 [5]中国地质科学院矿产资源研究所,北京100037

出　　处：《地质学报》2015年第3期569-582,共14页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划(973计划)(编号:2011CB403100);IGCP/SIDA600;国家自然科学基金(编号:41102033);(41472076);中国地质调查局地质调查项目(编号:1212011121253);(12120113037900);基本科研业务费专项项目(编号:53200959586)联合资助

摘　　要：西藏蒙亚啊矿床是冈底斯北缘Pb-Zn-Ag-Cu-Fe-Mo多金属成矿带内发育的Pb-Zn矿床的典型代表.对该矿床形成时代的精确厘定,是正确理解矿床成因机制,准确评价成矿潜力的关键。目前蒙亚啊矿床成矿时代的研究主要针对矿区内的花岗斑岩岩体或矿石矿物铅同位素展开,并存在较大的争议。本文基于成矿作用类型的差异,将蒙亚啊矿床的矿体进一步划分为矽卡岩型矿体和斑岩型矿体,而最具经济价值的硫化物成矿作用为矽卡岩型矿化。在此基础之上,通过云母Ar-Ar测年对蒙亚啊矽卡岩型矿体开展了定年工作。蒙亚啊矽卡岩型矿体中与闪锌矿共生的白云母的Ar-Ar同位素测年显示,其Ar-Ar坪年龄为54.60±0.40 Ma,正等时线年龄为54.45±0.67 Ma。根据白云母与矿石矿物的共生关系可知,该年龄应代表了蒙亚啊矿区矽卡岩型矿体的成矿时代。综合前人的研究结果,笔者认为:蒙亚啊Pb-Zn矿床存在两期成矿事件,但主成矿期形成于印度-欧亚陆-陆碰撞的主碰撞阶段,而新特提斯洋壳板片的回卷可能是矿床形成的深部动力学机制。Mengya＇a is a typical skarn-porphyry Pb-Zn deposit,located in the eastern part of the northern Gangdese Pb-Zn-Ag-Fe-Mo-W polymetallic belt（NGPB）.Constraining the mineralization age of Mengya＇a deposit is crucial to understand the genesis and geodynamic processes of this deposit and is important to estimate the metallogenic potential of the NGPB.Previous studies on the mineralization age of this deposit are mainly focused on the granite porphyry or lead isotopic composition of the sulfides,which are still disputed.According to the type of the mineralization,the orebodies of Mengya＇a deposit can be divided into skarn and porphyry styles,and the main economic orebodies are skarn style.Based on the geological characteristics of this deposit,we present the Ar-Ar dating results of muscovite collected from the skarn orebody,which is symbiosis with sphalerite.Muscovite from the Mengya＇a skarn orebody yielded a welldefined 40 Ar/39 Ar plateau age of 54.60 ± 0.40 Ma and an isochron age of 54.45 ± 0.67 Ma.These ages suggest that Mengya＇a skarn orebody were developed in the period of the main India-Eurasia collision.Combined with the former research,we suggest that there existed two phases mineralization of Mengya＇a deposit：the early skarn type and the late porphyry type,and the geodynamic processes which controlled the formation of the skarn mineralization was the rollback of the Neo-Tethys slab.

关 键 词：地质特征 Ar-Ar测年 地球动力学背景 西藏蒙亚啊 冈底斯北缘 

分 类 号：P618.4[天文地球—矿床学] P597.3[天文地球—地质学]