今天是2019年02月23日

内蒙古武川县赵井沟铌钽矿床成矿时代:来自LA-ICP-MS独居石、锆石U-Pb和黑云母40Ar-39Ar年龄的证据

DOI:10.3799/dqkx.2018.100

作者:李志丹,李效广,崔玉荣,李国占 ,张 佳 ,郭 虎 , 刘文刚 ,张超,俞礽安,谢瑜,王佳营

联系地址:中国地质调查局天津地质调查中心,天津 300170

摘要:内蒙古武川县赵井沟铌钽矿是新近取得勘查突破的一例大型铌钽矿床.矿体赋存岩石为含天河石钠长花岗岩,其次为花岗细晶岩、云英岩及天河石花岗伟晶岩.运用LA-MC-ICP-MS法对矿区钠长花岗(细晶)岩脉、正长花岗岩中的独居石、锆石进行了U-Pb同位素年龄测定,同时对石英-黑云母脉中的黑云母进行了40Ar-39Ar定年.4件独居石的LA-MC-ICP-MS U-Pb年龄分别为124±2 Ma(MSWD=2.9, n=27)、124±3 Ma(MSWD=2.0, n=46)、121±1 Ma(MSWD=3.3, n=43)和124±2 Ma(MSWD=3.2, n=12),1件锆石的LA-MC-ICP-MS U-Pb年龄为125±1 Ma(MSWD=1.6, n=18);黑云母40Ar-39Ar坪年龄为133.84±0.79 Ma(MSWD=3.31),40Ar/36Ar-39Ar/36Ar等时线年龄为134.55±0.79 Ma(MSWD=1.93),反等时线年龄为134.58±0.80 Ma(MSWD=1.99),这些年龄限定赵井沟铌钽矿形成于早白垩世.综合分析表明,燕山期是内蒙古地区重要的铌钽成矿期,赵井沟铌钽矿是燕山期伸展体制下构造岩浆活动的产物.

关键字:铌钽矿;成矿时代;独居石U-Pb定年;黑云母40Ar-39Ar定年;赵井沟;内蒙古;同位素

Yanshanian Mineralization of Zhaojinggou Nb-Ta Deposit, Inner Mongolia: Evidences from the Monazite and Zircon LA-MC-ICP-MS U-Pb and Biotite 40Ar-39Ar Geochronology

Author:Li Zhidan, Li Xiaoguang, Cui Yurong, Li Guozhan, Zhang Jia, Guo Hu, Liu Wengang, Zhang Chao, Yu Reng'an, Xie Yu, Wang Jiaying

Author Address:Tianjin Center of China Geological Survey, Tianjin 300170, China

Abstract:The Zhaojinggou Nb-Ta deposit is a newly explored large-scale deposit in Wuchuan County, Inner Mongolia. The Nb-Ta orebody is mainly hosted in the amazonite-bearing albite granite, and partly hosted in the granite aplite, greisen and amazonite granite pegmatite. In this paper, we use monazite and zircon LA-MC-ICP-MS U-Pb and biotite 40Ar-39Ar dating methods to constrain the mineralization age. Monazite LA-MC-ICP-MS U-Pb geochronological dating of four samples from granites yields ages of 124±2 Ma (MSWD=2.9,n=27), 124±3 Ma (MSWD=2.0, n=46), 121±1 Ma (MSWD=3.3, n=43) and 124±2 Ma (MSWD=3.2, n=12). One zircon sample from albite granite yields age of 125±1 Ma (MSWD=1.6, n=18). Meanwhile, biotite 40Ar-39Ar dating obtains the plateau age of 133.84±0.79 Ma (MSWD=3.31), isochron age of 134.55± 0.79 Ma (MSWD=1.93) and reverse isochron age of 134.58±0.80 Ma (MSWD=1.99). Therefore, all these ages constrain that the ore-forming period of Zhaojinggou Nb-Ta deposit is Early Cretaceous. In conclusion, the Zhaojinggou deposit resulted from the tectonic-magmatic activities of extensional setting, and the Yanshanian Period is the main Nb-Ta metallogenic age in Inner Mongolia.

Keyword:Nb-Ta deposit, mineralization age; monazite and zircon U-Pb dating; biotite 40Ar-39Ar dating; Zhaojinggou; Inner Mongolia; isotope.

 

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作者简介:李志丹(1986-),男,工程师,从事矿床学研究工作.ORCID: 0000-0002-3011-6392. E-mail: cugcug@qq.com

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