稀有气体同位素地球化学在矿床学研究中的应用进展  

Advances of noble gas isotope geochemistry application in the study of ore deposits

作　　者：武丽艳[1] WU LiYan(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550081

出　　处：《岩石学报》2019年第1期215-232,共18页Acta Petrologica Sinica

基　　金：中国科学院战略性先导专项(B类)(XDB18000000);国家重点研发项目(2016YFC0600207);国家自然科学基金项目(41773048)联合资助

摘　　要：稀有气体因其化学惰性以及在不同来源地质体中的同位素组成差异很大,在研究成矿流体来源、演化和壳-幔相互作用过程中具有非常重要的意义。另外,由于~4He、^(40)Ar是放射成因子体同位素,具有年代积累效应,因此,它们常被用于同位素测年。本文简要回顾了流体包裹体中稀有气体同位素的后生影响和样品、分析方法选择注意事项,以及近年来稀有气体同位素在成矿流体示踪,^(40)K-^(40)Ar、^(40)Ar-39Ar定年及(U-Th)/He定年方面的研究进展。已有研究证实流体包裹体中的稀有气体可能受后期扩散丢失、后生叠加和同位素分馏的影响,要根据目的选择不同的分析方法;稀有气体同位素可以示踪不同类型矿床的流体来源、演化及壳-幔相互作用、稀有气体同位素与卤素联合运用可以用来指示流体和盐度来源、演化过程以及矿物沉淀机制等,~3He/热的研究可以追溯流体的热源及其运移方式;流体包裹体^(40)Ar-^(39)Ar可以用于矿床直接定年,表生含钾矿物的^(40)K-^(40)Ar、^(40)Ar-^(39)Ar定年以及锆石、磷灰石和铁氧化物(U-Th)/He定年可为矿床及氧化带的形成时间、矿床形成后的抬升、剥露历史、古气候演化等重大地质问题讨论提供大量有意义的信息。Due to the chemical inertness and the distinct isotopic composition in different reservoirs,noble gas isotopes are playing important role in tracing ore-forming fluid origin,evolution and the process of crust-mantle interaction. Besides,as ^4He and ^40Ar has the effect of time accumulation,they are often used for dating. In this paper,we briefly reviews the modification of noble gas isotopes in fluid inclusions by post-entrapment processes and matters needing attention in the selection of samples and analytical methods,the progress of the noble gas in tracing ore-forming fluid origin,^40K-^40Ar and ^40Ar-^39Ar dating,as well as( U-Th)/He dating. We conclude that noble gas isotopes in fluid inclusions can be modified by addition of cosmogenic 3 He,in situ produced 4He and He loss.Analysis methods should be selected according to the purpose. Noble gas isotopes can be used to trace the origin and evolution of oreforming fluid,and crust-mantle interaction of different types of deposits. In addition,noble gas isotopes combined with halogens can be used to indicate the origin and evolution of ore-forming fluids and salinity,as well as the mechanism of mineral precipitation.3 He/heat ratio can be used to trace the heat source and its transport mode of fluid. The ^40Ar/^39Ar progressive crushing and stepwise heating techniques can be used to directly determine the mineralization ages of hydrothermal sulfide deposits.^40K-^40Ar and/or ^40Ar-^39Ar dating of supergene K-bearing minerals and( U-Th)/He dating of iron oxides can be used to determine the chronology of deposits and related oxidation zone. Based on the different close temperature of minerals,^40K-^40Ar and/or ^40Ar-^39Ar dating of K-bearing minerals and( UTh)/He dating of zircon,apatite and iron oxides provide a large amount of meaningful information for history of uplift and exhumation after deposit formation,and paleoclimate evolution.

关 键 词：稀有气体 流体示踪 ^3He/热 ^40Ar-^39Ar定年 (U-Th)/He定年 

分 类 号：P597[天文地球—地球化学]