内蒙古武川县赵井沟铌钽多金属矿床白云母^(40)Ar-^(39)Ar同位素年龄及地质意义  

^(40)Ar-^(39)Ar Dating of Muscovite from the Zhaojinggou Nb-Ta Polymetallic Deposit in Wuchuan County of Inner Mongolia and Its Geological Implications

作　　者：高允 孙艳[1] 赵芝[1] 李建康[1] 何晗晗[1] 杨岳清[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《岩矿测试》2017年第5期551-558,共8页Rock and Mineral Analysis

基　　金：国家自然科学基金资助项目"柴达木盆地大风山特大型天青石矿床锶的富集成矿机制研究"(41402084);中国地质调查局地质调查项目"我国三稀金属资源战略调查"(1212011220803);我国稀有;稀散资源战略调查及研究(1212011220805);中国矿产地质与成矿规律综合集成和服务(矿产地质志)(DD20160346)

摘　　要：内蒙古赵井沟铌钽多金属矿是近年来取得较大找矿进展的大型稀有金属矿床,初步探明铌钽氧化物储量超过8200吨,前人对其矿床地质特征已有初步研究,但其成矿时代尚未精确厘定。本文以赵井沟铌钽多金属矿区内天河石花岗伟晶岩脉中的白云母为研究对象,利用^(40)Ar-^(39)Ar同位素年代学方法,以确定其成矿时代。研究发现矿区内铌钽矿化主要赋存在碱长花岗岩、碱长花岗细晶岩、云英岩和天河石花岗伟晶岩中,且铌钽矿物与白云母同时形成,有重要的共生关系,故本次研究获得的白云母坪年龄123.57±0.66 Ma和等时线年龄124.0±2.0 Ma具有地质意义,可代表成矿年龄。这一成果表明赵井沟铌钽多金属矿床形成于燕山晚期(至少延续至早白垩世),与前人获得的锆石年龄有较大差异,这对分析其矿床成因有重要意义。同时,结合区域地质资料,本文认为华北地台北缘内蒙古地轴中部在燕山运动的晚期存在一次重要的稀有金属成矿事件。The Zhaojinggou Nb-Ta polymetallic deposit in Inner Mongolia is a newly discovered large rare metal ore deposit.The reserve of Nb-Ta oxides is more than 8200 tons.Previous studyfocus on geological features of this deposit,but they the precise mineralization age remains unknown.In this paper,muscovite in amazonite granite pegmatite was used to constrain the timing of mineralization using ^(40)Ar-^(39)Ar isotope method.Results show that Nb-Ta mineralization is mainly hosted in alkali-feldspar granite,alkali-feldspar aplite,greisen,and amazonite granite pegmatite.According to the geologicalrelationship between Nb-Ta minerals and muscovite,we can infer that Nb-Ta minerals and muscovite are formed at the same time.Thus,the muscovite plateau ages of 123.57 ± 0.66 Ma and 124.0 ± 2.0 Ma can represent the mineralization age.Results show that the Zhaojinggou Nb-Ta polymetallic deposit was formed at late Yanshanian( or at least Early Cretaceous),the ^(40)Ar-^(39)Ar age have bigger difference with the zircon age,which is of great importance for ore genesis.Combining with regional geology,the author thinks that an essential rare-metal mineralization happened in the middle part of inner Mongolian axis on the north margin of north china platform during the late Yanshan movement.

关 键 词：铌钽多金属矿床 天河石花岗伟晶岩 白云母 40Ar-39Ar同位素年龄 赵井沟 

分 类 号：P618.79[天文地球—矿床学] P618.86[天文地球—地质学]