单种矿物单颗粒Rb-Sr同位素等时线定年的成矿年代学应用前景  

Application prospect of the single-grain mineral Rb-Sr isotopic isochron dating in metallogenic geochronology

作　　者：何俊 齐泽秋 李为用 王智毅 赵静欣 肖平[1,2] 贺剑峰 HE Jun;QI Zeqiu;LI Weiyong;WANG Zhiyi;ZHAO Jingxin;XIAO Ping;HE Jianfeng(Key Laboratory of Crust-Mantle Materials and Environments,Chinese Academy of Sciences,Hefei 230026,Anhui,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui,China)

机构地区：[1]中国科学院壳幔物质与环境重点实验室,安徽合肥230026 [2]中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《华东地质》2024年第1期16-25,共10页East China Geology

基　　金：国家自然科学基金“单颗粒矿物Rb-Sr同位素稀释法定年技术及其在金属矿床年代学的应用(编号:42202069)”;“澜沧江古特提斯构造单元构造属性与晚古生代—早中生代岩浆岩成因研究(编号:42172051)”项目联合资助。

摘　　要：矿床成矿年龄的厘定一直是矿床学研究中的重点和难点,也是深入研究矿床成因的基础。然而,由于缺少合适的定年矿物、不同矿物之间同位素平衡以及矿物多期生长等因素,长期以来通过同位素定年技术确定成矿年龄还存在诸多限制。不同学者或不同体系同位素定年结果常常存在明显差异,严重制约了矿床成因和成矿系统的深入研究,也难以为找矿勘查工作提供有效的理论依据。近年来,随着化学分离纯化技术和热电离质谱计性能的提高,可以准确测试低含量样品的同位素组成,进而为单颗粒矿物同位素定年提供了技术前提。文章简要回顾了Rb-Sr同位素等时线定年技术在矿床成因研究中的应用,重点介绍单种矿物单颗粒Rb-Sr同位素等时线定年技术的优点和难点。结果表明:相较于传统的Rb-Sr同位素等时线定年,单种矿物单颗粒等时线定年可以最大限度地满足“同时、同源、封闭、平衡”的同位素定年基本原则。在同种矿物不同颗粒中,母体与子体同位素87 Rb/86 Sr比值的差异可以达到最大范围,进而有助于获得高质量的等时线,得到高精度的成矿年龄。单种矿物单颗粒Rb-Sr同位素等时线定年技术能够有效地突破矿床定年的技术瓶颈,为诸多类型的热液矿床成矿年龄厘定和矿床研究提供重要基础。Ore-forming age dating of ore deposits has been one of the key and problematic factors in metallogeny study and is of the fundament for understanding the metallogenic genesis.Due to the lack of suitable minerals for the dating,isotopic equilibrium between different minerals,multi-stage formation of minerals and other factors,the precise dating of ore deposits by isotopic methods still has many technological limits for a long time.Remarkably inconsistent dating results acquired by different researchers or different isotopic systems always seriously hinder intensive studies on metallogenic genesis,which in turn is hard to support the ore exploration.In recent years,the improvements of separation and purification of elements and isotopic measurement with thermal ionization mass spectrometer(TIMS)ensure the accurate measurements of isotopic composition in micro-samples,providing possibility for the isotopic dilution dating of single-grain minerals.After briefly reviewing the applications of the Rb-Sr isotopic isochron dating technique in the metallogenic genesis,this paper emphatically introduced the advantages and difficulties of the Rb-Sr isotopic dating via the isochron method of single-grain minerals.In comparison to traditional Rb-Sr isotopic dating,the Rb-Sr isotopic isochron dating of single-grain minerals can match the fundamental principles of the isochron dating to the hilt,namely:simultaneity,homogeneity,isotopic closure and equilibrium of minerals.Different parent/daughter ratios existing in different grains of the same mineral can reach to the maximum extent,so that it can improve the quality of such isochron and then yield more accurate isochron ages.The Rb-Sr isotopic isochron dating of single-grain minerals can prospectively break through the long-standing“choke point”of the ore deposits dating,offering extensive application in the age-dating of various hydrothermal deposits and contributing intensive studies on the mineralization.

关 键 词：地质年代学 热液矿床 矿床定年 单颗粒矿物 RB-SR同位素 

分 类 号：P597.3[天文地球—地球化学]