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《矿物岩石地球化学通报》2018,(5)
微区原位同位素分析是近年来同位素地球化学研究的前沿领域。其中,激光剥蚀系统与多接收电感耦合等离子体质谱联用技术(LA-MC-ICP-MS)被广泛应用于不同同位素体系和不同天然矿物的微区原位同位素测定。铅同位素作为有效的地球化学示踪手段被广泛用于岩石成因和演化、成矿时代、成矿物质来源、环境污染物源示踪和考古学等研究。目前多利用LA-MC-ICP-MS测定硅酸盐矿物、硫化物矿物和包裹体Pb同位素组成。该方法省略了冗长的化学处理流程,提高了工作效率,并且通过对不同矿物或同一矿物中不同结构部位进行微区原位Pb同位素分析,可揭示微米尺度上的Pb同位素组成变化,为解决地质问题提供了重要的证据。本文评述了近年来地质样品中LA-MC-ICP-MS测定Pb同位素的方法改进及其在部分地球科学研究中的应用。 相似文献
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高温熔融研制钾长石玻璃标准物质初探 总被引：1，自引：1，他引：0
激光剥蚀多接收等离子体质谱(LA-MC-ICPMS)是进行原位微区分析微量元素和同位素的重要技术之一,标准样品与样品之间的基体匹配是解决影响该技术准确分析的基体效应和分馏效应的首选方案。长石(特别是长石微区)的Pb同位素组成是示踪岩石形成和演化历史的重要途径,而LA-MC-ICPMS技术则是进行长石Pb同位素原位微区分析的关键技术,然而目前国内外尚没有合适的长石Pb同位素分析标准。文章研究探讨了利用高温炉进行原位微区分析钾长石中Pb同位素组成所用外部标准物质合成条件,结果表明,常规的74μm(200目)碎样无法得到均一的钾长石玻璃,需要将初始钾长石粉末研磨至1300目以下;高温炉合成温度为1680℃;熔融时间为2 h;采用液氮方式淬火。制成的钾长石玻璃除表面具有轻微的不均一性外,内部的Pb同位素比值为1.90779±0.00009(208Pb/206Pb,2s),0.75899±0.00004(207Pb/206Pb,2s),20.909±0.002(206Pb/204Pb,2s),15.871±0.002(207 Pb/204 Pb,2s)和39.888±0.005(208 Pb/204 Pb,2s),相应的相对标准偏差(RSD)分别为0.007%、0.008%、0.016%、0.016%和0.021%。表明利用本研究方法合成的钾长石玻璃可作为潜在的钾长石中Pb同位素组成原位微区分析外部校准物质。 相似文献
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应用多接收电感耦合等离子质谱(MC-ICP-MS)等分析技术进行铊(Tl)同位素分析已成为非传统稳定同位素地球化学研究的重要内容之一.对近年来Tl同位素的实验测试方法及其地质应用的有关研究进展做了详细论述,包括Tl的地球化学行为、Tl同位素分析测试技术、同位素分馏机理、在各地质储库中的组成特征以及Tl同位素的地质应用等多个方面.这些研究表明该分析技术为行星科学、古海洋学、地幔地球化学、岩石成因以及矿床学等领域的研究提供了其他同位素分析方法难以获得的重要信息,充分展示了该分析技术在地球科学和环境科学领域的应用前景. 相似文献
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铁同位素分析测试技术研究进展 总被引：5，自引：3，他引：2
铁是地球上丰度最高的变价元素,在自然界大量分布于各类矿物、岩石、流体和生物体中,并广泛参与成岩作用、成矿作用、热液活动和生命活动过程。铁同位素组成对地球化学、天体化学和生物化学方面提供重要的信息,是同位素地球化学研究领域的热点。铁同位素的精确测量是开展相关研究的重要基础。本文评述了铁同位素测试技术的研究进展,主要包括:①溶液法测试铁同位素样品纯化过程中阴离子树脂的改进;②质谱分析从传统的热电离质谱法发展为多接收电感耦合等离子体质谱法;③激光微区原位测试技术的研发等。在此基础上,对测试过程中会导致产生铁同位素分馏的步骤和校正方法进行了总结,并对各种测试方法的优缺点进行了评述。本文认为:溶液法分析流程长且复杂,但分析精度高(0.03‰,2SD)、方法稳定;微区原位分析方法从纳秒激光剥蚀发展为飞秒激光剥蚀,脉冲持续时间更短、脉冲峰值强度更高(可达10~(12)W),聚焦强度超过10~(20)W/cm~2,使其具有分析速度快、空间分辨率高的优势。微区原位法可以从微观角度去讨论铁同位素变化的地球化学过程,但基体效应的存在限制了微区原位铁同位素的广泛应用。因此,缩短溶液法分析流程,开发系列基体匹配的标准样品,是铁同位素分析方法研发的方向。 相似文献
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西藏甲玛斑岩-矽卡岩型铜多金属矿床的成矿期次可划分为成矿前斯和矽卡岩成矿期(铜钼阶段、铜铋阶段、铁铜阶段和铜铅锌阶段)。应用飞秒激光剥蚀多接收等离子体质谱(fsLA-MC-ICP-MS)对甲玛矿床主要矿石中的硫化物和斑岩中的长石斑晶进行原位微区Pb同位素组成分析,测定结果与前人运用化学溶样法获得的Pb同位素组成基本一致,表明原位Pb同位素分析技术具有很高的可靠性,不同成矿阶段的硫化物的Pb同位素组成总体一致表明成矿物质来自同一岩浆源区。斜长石和钾长石的Pb同位素组成对比研究显示,花岗斑岩与甲玛矿床的形成有直接成因联系,而花岗闪长斑岩很可能与成矿作用无关。通过对甲玛成矿物质来源的研究表明,有较多幔源物质加入的新生加厚下地壳部分熔融形成的岩浆为甲玛超大型矿床的形成提供了充足的Cu、Au等成矿物质。 相似文献
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激光剥蚀等离子质谱微区分析在固体地球科学中的应用进展 总被引：5，自引：1，他引：5
当前分析化学技术正向着痕量微区方向发展。这使得我们能够用更小更少的样品直接得到更多的地球化学信息。在诸多微区测试技术中,激光剥蚀等离子质谱（LA-ICPMS）技术发展最快。其地质应用较广,激光探针等离子体质谱能够进行固体样品的微区微量元素和同位素的分析,具有灵敏度高、简便、快速的特点,同样具有在同位素定年上的潜力。近年来又研制出激光剥蚀多道接收等离子质谱（LA-MC-ICPMS）仪,使得微区同位素分析开始了新的革命。而多种微区技术综合应用为近几年分析地球化学新的趋势。 相似文献
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含U副矿物的原位微区U-Pb定年方法 总被引：3，自引：0，他引：3
同位素地质年代学是解决地质体时、空演化及大陆动力学等地学研究的基础,而副矿物U-Pb年代学是常用的定年方法之一。含U副矿物广泛分布于各种类型的岩石中,其U[CD*2]Pb年龄可提供地质体演化过程中所发生的地质事件的时代,而传统的热电离质谱全溶年代学分析只能提供样品年龄信息的平均值。随着仪器科学和分析技术的进步,副矿物的原位微区U-Pb测年方法成为近年来U-Pb同位素地质年代学发展的主导趋势。与锆石相比,其它副矿物的U-Pb同位素体系相对比较复杂,经常含较高的普通Pb。在仔细阅读相关文献的基础上,结合近年来相关研究工作,综述副矿物原位微区U-Pb定年以及普通Pb校正方法研究的最新进展,以期推动我国副矿物原位微区U-Pb定年方法相关研究及其在地质学中的应用。 相似文献
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随着超净化实验室条件的完善以及多接收同位素质谱技术的成熟，铅同位素双稀释法倍受关注。用双稀释法测定铅同位素比值的方法原理，以及^204Pb—^207Pb双稀释剂的配制和标定方法。通过对标准物质NBS981和地质样品的分析测定，表明用双稀释法测定铅同位素比值，可以有效校正由质谱分析造成的同位素分馏效应，从而提高分析结果的精度和准确度。 相似文献
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Precise and accurate in situ Pb-Pb dating of apatite, monazite, and sphene by laser ablation multiple-collector ICP-MS 总被引：3，自引：0，他引：3
B.J.A WilligersJ.A Baker E.J KrogstadD.W Peate 《Geochimica et cosmochimica acta》2002,66(6):1051-1066
To evaluate in situ Pb dating by laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), we analysed apatite, sphene, and monazite from Paleoproterozoic metamorphic rocks from West Greenland. Pb isotope ratios were also determined in the National Institute of Standards and Technology (NIST) 610 glass standard and were corrected for mass fractionation by reference to the measured thallium isotope ratio. The NIST 610 glass was used to monitor Pb isotope mass fractionation in the low Tl/Pb accessory minerals. Replicate analyses of the glass (1 to 2 min) yielded ratios with an external reproducibility comparable to conventional analyses of standard reference material 981 by thermal ionisation mass spectrometry (TIMS). Mineral grains were generally analysed with a 100-μm laser beam, although some monazite crystals were analysed at smaller spot sizes (10 and 25 μm). The common Pb isotope ratios required for age calculations were either measured on coexisting plagioclase by LA-MC-ICP-MS or could be ignored, as individual crystals exhibit sufficient Pb isotopic heterogeneity to perform isochron calculations on replicate analyses of single crystals. Mean mineral ages with the 204Pb ion beam measured in the multiplier were as follows: apatite, 1715 ± 23 m.y.; sphene, 1789 ± 11 m.y.; and monazite, 1783 to 1888 m.y., with relative uncertainties on individual monazite ages of <0.2% but highly reproducible age determinations on single monazite crystals (?1%). Isochron ages calculated from several mineral analyses without assumption of common Pb also yield precise age determinations. Apatite and monazite Pb ages determined by in situ Pb isotope analysis are identical to those determined by conventional TIMS analysis of bulk mineral separates, and the analytical uncertainties of these short laser analyses with no prior mechanical or chemical separation are comparable to those obtained by TIMS. Detailed examination of the sphene in situ age data does, however, show a small discrepancy between the LA-MC-ICP-MS and TIMS ages (∼1% younger). High-resolution mass scans of the sphene during ablation clearly showed several small and as yet unidentified isobaric interferences that overlap with the 207Pb peak at the resolution conditions for measurement of isotope ratios. These might account for the age discrepancy between the LA-MC-ICP-MS and TIMS sphene ages. LA-MC-ICP-MS is a rapid, accurate, and precise method for in situ determination of Pb isotope ratios that can be used for geochronological studies in a manner similar to an ion microprobe, albeit currently at a somewhat degraded spatial resolution. Further modifications to the LA-MC-ICP-MS system, such as improved sensitivity, ion transmission, and LA methodology, may lead to this type of instrument becoming the method of choice for many types of in situ Pb isotope dating. 相似文献
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The development of the MC-ICP-MS method, which was launched about one decade ago and was largely stimulated by the need to solve geological problems, has opened a new avenue in isotope mass spectrometry. One of the advantages of this method is the possibility of applying a newly developed approach to the correction of analytical results for the effect of mass discrimination by normalizing the measured isotope ratios of an element to a reference (standard) isotope ratio of another element. This makes it possible to overcome the main disadvantage of conventional thermal ionization mass spectrometry (TIMS), in which the effect of mass discrimination cannot be fully taken into account during isotope analysis, and thus to implement a highly accurate method for the analysis of Pb-isotope composition. In application to the capability of the NEPTUNE MC-ICP mass spectrometer, we optimized and calibrated a method for high-accuracy Pb isotope analysis in solutions spiked with Tl, with all currently measured Pb-isotope ratios normalized to the standard 205Tl/203Tl ratio (TLN-MC-ICP-MS). The factors affecting the random and systematic analytical errors were examined, and the optimal operating regime and analytical conditions were determined. Much attention was paid to the correlation of the measurement results and the mass discrimination effect determined from the 205Tl/203Tl ratio. The value of the 205Tl/203Tl normalizing ratio was analytically determined through isotope analyses of the NIST SRM 981, and SRM 982 standard samples of Pb-isotope composition. The data obtained for two mixtures Tl + Pb (SRM 982) and Tl + Pb (SRM 981) in ten replicate analyses were 2.38898 ± 12 and 2.38883 ± 20, respectively. These results are in good mutual agreement, and their general mean 205Tl/203Tl = 2.3889 ± 1 coincides (within the error) with the recently published values of 2.3887 ± 7 [Collerson et al., 2002] and 2.3889 ± 1 [Thirlwall, 2002]. The precision of the method (±2SD), which was assayed by the long-term reproducibility of the results of replicate analyses of SRM 981 and seven galena samples (90 analyses) was 0.016–0.018% for the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios and 0.005 and 0.009% for the 207Pb/206Pb and 208Pb/206Pb ratios, respectively. The precision of the isotope analysis of common Pb was significantly improved (by factors of 6–10 for various isotope ratios) compared with the precision of TIMS techniques acceptable in isotope studies during three decades. The described method was applied to examine the Pb-isotope composition of approximately 250 samples of galena, scheelite, and pyrite from a number of well known (including large) gold, sulfied, and base-metal deposits. The precision of the method (0.01–0.02%) makes it possible to study small inter-and intra-phase differences in Pb-isotope ratios in hydrothermal and magmatic rocks, to assay the scale of regional and variations in the isotope composition of ore Pb, and to correlate the Pb-isotope composition of rocks and ores and reveal its evolutionary trends. 相似文献
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AG-MP-1M阴离子交换树脂分离-表面热电质谱法测定沉积物中的铅同位素组成 总被引：2，自引：1，他引：1
利用新型阴离子交换树脂分离沉积物中的重金属Pb,采用表面热电离质谱法(TIMS)测定了沉积物样品中的Pb同位素组成。新型树脂为大孔径阴离子树脂AG-MP-1M,淋洗液采用低浓度的盐酸,避免了使用难以纯化的氢溴酸,可有效地降低试剂空白。通过对铅同位素标准物质NIST NBS-981的重复测试,方法的精密度(<0.5%,2s)和准确度均达到了应用研究的要求。对5个实际沉积物样品中的铅同位素组成进行测定,获得了理想的分析效果。 相似文献
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NIU Yaoling 《《地质学报》英文版》2003,77(1):44-58
The authors measured Pb isotope compositions of seven USGS rock reference standards, i.e. AGV-1, AGV-2, BHVO-1, BHVO-2, BCR-2, BER-1/1 and W-2, together with NBS 981 using a micromass isoprobe multi-collector inductively-coupled plasma mass spectrometer (MC-ICP-MS) at the University of Queensland. 203Tl-205Tl isotopes were used as an internal standard to correct for mass-dependant isotopic fractionation. The results for both NBS 981 and USGS rock standards AGV-1 and BHVO-1 are comparable to or better than double- and triple-spike TIMS (thermal ionization mass spectrometry) data in precision. The data for BHVO-2 and, to a lesser extent, AGV-2 and BCR-2 are reproducibly higher for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb than double-spike TIMS data in the literature. The authors also obtained the Pb isotope data for BIR-1/1 and W-2, which may be used as reference values in future studies. It is found that linear correction for Pb isotopic fractionation is adequate with the results identical to those corre 相似文献
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本文以稀土矿床中的常见副矿物氟碳铈矿为研究对象,通过优化实验条件和仪器参数,分别采用激光剥蚀多接收电感耦合等离子体质谱法(LA-MC-ICP-MS)和同位素稀释热电离质谱法(ID-TIMS)对氟碳铈矿样品SAM进行U-Pb定年技术研究,并将此两种方法得到的结果进行对比。LA-MC-ICP-MS得到的U-Pb年龄为(409±18)Ma(N=27,MSWD=4.5),ID-TIMS得到的206Pb/238U U-Pb年龄为(407.8±3.3)Ma(N=3,MSWD=0.029),两种方法得到的U-Pb年龄结果在误差范围内一致。通过比较两种方法的实验流程和结果,总结了各自的优缺点,为氟碳铈矿U-Pb定年方法选择提供了参考依据。 相似文献
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Inductively coupled plasma-mass spectrometry (ICP-MS) is capable of measuring isotopic and elemental abundances in geologic materials easily and rapidly. Although the precision of isotope ratio data obtained by ICP-MS is inferior to that by thermal ionization mass spectrometry, it is adequate for application to a number of geochemical exploration problems.National Institute of Standards and Technology (NIST) Pb metal standard reference material 981 (NBS981), was used as the isotopic standard to correct the measured isotope intensities for mass discrimination. The mean relative standard deviation (RSD) of the determinations of the abundances of 206Pb, 207Pb, and 208Pb in the two other NIST Pb isotope reference materials, NBS981 and NBS982, was better than 0.3%, whereas the RSD for the determination of the less abundant 204Pb was 0.4%. Accuracy was demonstrated by repeated analysis of NBS981, NBS982, and NBS983. The Student t-statistic ranged between −1.75 and 2.04 for the abundances of the 4 Pb isotopes in the three NIST materials.Data from a suite of 13 uraninite-rich samples from Labrador demonstrate the ability of ICP-MS to determine age and geochemical information sufficient for regional interpretations. The determined radiogenic 207Pb/206Pb ratios of 12 of the samples give ages between 1697 and 1805 Ma with average uncertainties (one standard deviation) of 4 Ma, whereas one of the samples has an age of 495 ± 4 Ma. The average age of the 12 samples was 1752 ± 27 Ma. Along with the Pb isotope intensities, 232Th and 238U were measured and the U-Pb age determined from a fit of the 206Pb/238U vs. 207Pb/235U for 9 of the samples. The concordia intercept age of 1740 Ma for the best-fit line is in good agreement with the mean 207Pb/206Pb age of 1752 Ma. 相似文献
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VizualAge, a new computer software tool for analysing U‐Pb data obtained by laser ablation‐inductively coupled plasma‐mass spectrometry, was developed. It consists of a data reduction scheme (DRS) for Iolite (a general mass spectrometry data analysis tool) as well as visualisation routines. In addition to the U/Pb and Th/Pb ages calculated by Iolite’s U‐Pb geochronology DRS, VizualAge also calculates 207Pb/206Pb ages and common Pb corrections for each time‐slice of raw data. Importantly, VizualAge allows one to display a live concordia diagram for visualising data on such a diagram as an integration interval is being adjusted. This provides instantaneous feedback regarding discordance, uncertainty, error correlation and common Pb. Several zircon data sets were used to illustrate how the live concordia could be used as a powerful inspection tool, revealing a single analysis to consist of zones of concordance, metamict areas, as well as inherited cores or younger overgrowths. VizualAge also constructs histograms, conventional and Tera‐Wasserburg type concordia diagrams, as well as 3D U‐Th‐Pb and total U‐Pb concordia diagrams. The precision and accuracy of data reduced with VizualAge are demonstrated with examples of the Ple?ovice, Temora‐2 and Penglai zircon reference materials. Data for zircon from the Long Lake Batholith (Wyoming craton) were used to illustrate how VizualAge calculated common Pb corrections and helped to expose as yet unexplained difficulties with accurately determining 204Pb. 相似文献
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Deposition and remobilization of uranium in the North Baikal region: Evidence from the U-Pb isotopic systems of uranium ores 总被引：1，自引：0，他引：1
Based on the study of local volumes of minerals, including their microsampling and subsequent analysis of Pb/Pb and U/Pb isotope ratios with the classic methods of isotopic dilution and thermoionization mass spectrometry (TIMS), U-Pb and Pb-Pb isotopic datings of minerals were carried out in uranium ores from deposits in the Akitkan and Nechera-Nichatka ore districts (North Baikal region). Reliable evidence in favor of the Middle Devonian (384 ± 8 Ma) remobilization of Paleoproterozoic primary uranium concentrations and the redeposition of uranium as pitchblende 2 has been obtained for the first time for ores of the Akitkan district. The Paleoproterozoic (1832 ± 13 Ma) age of uraninite mineralization and the timing of the latest (377 ± 5 Ma) transformation of uranium ores at the Chepok deposit (Nechera-Nichatka district) are substantiated. 相似文献