摘要
对于不同类型的地球化学勘查样品 ,运用恰当的分析方法处理 ,是成功地发现矿床的关键。激光熔融电感耦合等离子质谱分析 ,即LA ICPMS ,是功能最强的多元素分析技术之一。该方法获得数据快捷 ,样品制备简单 ,其高灵敏度为很多主元素和微量元素 (包括铂族元素、稀土元素、高场强元素和多种成矿示踪元素 )提供了低检测限 ,正在并将要持续为地球化学应用提供新的信息。仪器由ICPMS(四极 ,多接受或磁扇域 )附加激光器 (紫外或红外波长 )而构成。应用于地球科学研究的标准仪器的激光器为具有 2 6 6nm四倍频率的Nd :YAG激光器 ,或者是具有 193nm波长的ArF激态原子激光器。激光器熔融样品 ,并通过运载气体将熔融的样品物质传送到IP ,而不是将样品溶解后 ,通过雾化器和雾化室将样品传输给ICP。这就使我们能够进行微区分析 ,如矿物环带 ,或者矿物中的微小矿物、融体和流体包裹体等。运用外标校对元素比值 ,并结合内标使用 ,可以获得定量测试结果。对于固体熔融物的分析精度一般为 2 %～ 5 %RSD(相对标准误差 ) ,对于流体包裹体则为 10 %～ 30 %RSD。LA ICPMS的一些复杂系统可能引起成分分馏和质量干扰。对于分馏效应 ,可以通过运用产生小粒子的短波长激光器和运用He作为运载气体来减小 ;对于质量干扰 ,则可以通过?
Applying the appropriate analytical methods that deal with the different sample types from geochemical exploration is critical for successful ore deposit discoveries. One of the most versatile multi element techniques is laser ablation inductively coupled plasma mass spectrometry (LA ICPMS). Its fast data acquisition, minimal sample preparation and high sensitivity offering low detection limits for a wide range of major and trace elements, including PGE, REE, HFSE, and many pathfinder elements, is adding and will continue to add new information to geochemical applications.The instrument consists of a laser (UV or IR wavelength) that is attached to an ICPMS (quadrupole, multi collector or magnetic sector field). The standard instruments used for application in Earth Sciences consist of a Nd:YAG laser commonly with a quadrupled frequency of 266 nm or ArF Excimer lasers with a wavelength of 193 nm. Rather than having the sample dissolved and introduced via a nebulizer and a spray chamber into the ICP, the laser is ablating the sample and a carrier gas transports the ablated material to the ICP. This allows for spatially controlled analyses of mineral zones or small mineral, melt and fluid inclusions within a host mineral. External standards are used to calibrate relative element ratios and by using an internal standard, quantitative results are obtained. Analytical precision is normally between ±(2%～5%)RSD for solid ablation and for fluid inclusions ±(10%～30%)RSD. Some of the complications of LA ICPMS involve fractionation and mass interferences. Using a short wavelength laser that produces small particles and using He as a carrier gas minimizes fractionation. Mass interferences can be overcome to some extend by using high resolution mass spectrometers or having a dynamic reaction cell or collision cell introduced.The focus of this paper is fluid inclusion microanalysis and a short review and several case studies shall illustrate the progress and potential of LA ICPMS in this field. Quantitative fluid inclusion analyses of single inclusions reveal a new type of geochemical information that was previously not available or had to be indirectly estimated by e.g., mineral chemistries and experimentally obtained partitioning coefficients. The new geochemical information from fluid inclusion analyses can be used as input for geochemical models that are used to model ore formation and fluid/rock interactions. In this respect, the data contribute to refine the models on which mineral exploration is based and may enhance the chances for finding new ore deposits.
出处
《地学前缘》
EI
CAS
CSCD
2003年第2期379-393,共15页
Earth Science Frontiers
基金
ARC基金 (澳大利亚基金会基金 )项目
