Overcoming analytical limitations with 5-line multi-dynamic Nd isotope measurements by thermal ionisation mass spectrometry

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-02-15 DOI:10.1016/j.chemgeo.2025.122686

C. Israel , C. Chauvel , T.-H. Luu , E.C. Inglis , D. Roberts

{"title":"Overcoming analytical limitations with 5-line multi-dynamic Nd isotope measurements by thermal ionisation mass spectrometry","authors":"C. Israel , C. Chauvel , T.-H. Luu , E.C. Inglis , D. Roberts","doi":"10.1016/j.chemgeo.2025.122686","DOIUrl":null,"url":null,"abstract":"<div><div>The extinct 146Sm<img>142Nd radio-isotope chronometer is a valuable tool to study the first 500 Myr of Earth's history, although the entire range of variations of the 142Nd/144Nd ratio in terrestrial materials is on the order of 20 ppm only. The challenge is that measuring small isotope variations needs very high precision measurements (better than 5 ppm), which are difficult to obtain.</div><div>Here we present high-precision measurements of Nd isotope ratios performed over a period of three years using the latest generation Thermal Ionisation Mass Spectrometer (TIMS) developed by Nu Instruments – Nu TIMS. The Nu TIMS comprises 16 fixed Faraday cups and a zoom optics system that allow 5-line multi-dynamic analyses with the acquisition of three dynamic ratios for all Nd isotopes. This new method, coupled with an enhanced Nd+ signal provides precise measurements with internal errors lower than 2 ppm on 142Nd/144Nd.</div><div>We assess the performance of the method using multiple measurements of JNdi-1 and AMES Rennes Nd pure standards, together with rock reference materials. For example, typical JNdi-1 measurements performed over a period of 19 months average at 142Nd/144Nd = 1.1418299 ± 36 (2sd – 3.2 ppm), 143Nd/144Nd = 0.5121007 ± 10 (2.0 ppm), 145Nd/144Nd = 0.3484046 ± 6 (1.8 ppm), 148Nd/144Nd = 0.2415790 ± 10 (4.1 ppm) and 150Nd/144Nd = 0.2364481 ± 27 (11.3 ppm). With such precision and accuracy, subtle variations of 142Nd/144Nd ratios, as low as 3 ppm, can now be detected in natural samples.</div><div>Minute differences in 145Nd/144Nd, 148Nd/144Nd and 150Nd/144Nd ratios can now also be detected in natural samples, allowing better identification of nucleosynthetic anomalies in extra-terrestrial samples. For terrestrial samples, it allows detection of traces of samarium, and of nuclear field shift effect due to analytical issues. In particular, we demonstrate that some Sm is present in the JNdi-1 standard and affects both its 148Nd/144Nd and 150Nd/144Nd ratios, making a systematic interference correction necessary. By detecting the existence of nuclear field shift effect on Nd isotopes, we can now prevent mis-interpretations of 142Nd/144Nd deviations that could be wrongly attributed to radiogenic signatures acquired during the Hadean.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122686"},"PeriodicalIF":3.6000,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chemical Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0009254125000762","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}

引用次数: 0

Abstract

The extinct ¹⁴⁶Sm¹⁴²Nd radio-isotope chronometer is a valuable tool to study the first 500 Myr of Earth's history, although the entire range of variations of the ¹⁴²Nd/¹⁴⁴Nd ratio in terrestrial materials is on the order of 20 ppm only. The challenge is that measuring small isotope variations needs very high precision measurements (better than 5 ppm), which are difficult to obtain.

Here we present high-precision measurements of Nd isotope ratios performed over a period of three years using the latest generation Thermal Ionisation Mass Spectrometer (TIMS) developed by Nu Instruments – Nu TIMS. The Nu TIMS comprises 16 fixed Faraday cups and a zoom optics system that allow 5-line multi-dynamic analyses with the acquisition of three dynamic ratios for all Nd isotopes. This new method, coupled with an enhanced Nd⁺ signal provides precise measurements with internal errors lower than 2 ppm on ¹⁴²Nd/¹⁴⁴Nd.

We assess the performance of the method using multiple measurements of JNdi-1 and AMES Rennes Nd pure standards, together with rock reference materials. For example, typical JNdi-1 measurements performed over a period of 19 months average at ¹⁴²Nd/¹⁴⁴Nd = 1.1418299 ± 36 (2sd – 3.2 ppm), ¹⁴³Nd/¹⁴⁴Nd = 0.5121007 ± 10 (2.0 ppm), ¹⁴⁵Nd/¹⁴⁴Nd = 0.3484046 ± 6 (1.8 ppm), ¹⁴⁸Nd/¹⁴⁴Nd = 0.2415790 ± 10 (4.1 ppm) and ¹⁵⁰Nd/¹⁴⁴Nd = 0.2364481 ± 27 (11.3 ppm). With such precision and accuracy, subtle variations of ¹⁴²Nd/¹⁴⁴Nd ratios, as low as 3 ppm, can now be detected in natural samples.

Minute differences in ¹⁴⁵Nd/¹⁴⁴Nd, ¹⁴⁸Nd/¹⁴⁴Nd and ¹⁵⁰Nd/¹⁴⁴Nd ratios can now also be detected in natural samples, allowing better identification of nucleosynthetic anomalies in extra-terrestrial samples. For terrestrial samples, it allows detection of traces of samarium, and of nuclear field shift effect due to analytical issues. In particular, we demonstrate that some Sm is present in the JNdi-1 standard and affects both its ¹⁴⁸Nd/¹⁴⁴Nd and ¹⁵⁰Nd/¹⁴⁴Nd ratios, making a systematic interference correction necessary. By detecting the existence of nuclear field shift effect on Nd isotopes, we can now prevent mis-interpretations of ¹⁴²Nd/¹⁴⁴Nd deviations that could be wrongly attributed to radiogenic signatures acquired during the Hadean.

查看原文本刊更多论文

利用热电离质谱法克服5线多动态Nd同位素测量的分析局限性

已灭绝的146sm142号放射性同位素计时器是研究地球历史前500 Myr的一个有价值的工具，尽管陆地物质中142号/144Nd比率的整个变化范围仅为20 ppm。挑战在于，测量小的同位素变化需要非常高精度的测量（高于5ppm），而这很难获得。在这里，我们介绍了使用Nu Instruments开发的最新一代热电离质谱仪（TIMS）在三年内进行的Nd同位素比率的高精度测量- Nu TIMS。Nu TIMS包括16个固定法拉第杯和一个变焦光学系统，允许对所有Nd同位素进行5线多动态分析，并获得三个动态比。这种新方法与增强的Nd+信号相结合，在142 /144Nd上提供精确的测量，内部误差低于2 ppm。我们通过多次测量JNdi-1和AMES Rennes Nd纯标准以及岩石参考材料来评估该方法的性能。例如，典型的JNdi-1测量在19个月的平均时间内进行，142 /144Nd = 1.1418299±36 (2sd - 3.2 ppm), 143Nd/144Nd = 0.5121007±10 (2.0 ppm), 145Nd/144Nd = 0.3484046±6 (1.8 ppm), 148Nd/144Nd = 0.2415790±10 （4.1 ppm）和150Nd/144Nd = 0.2364481±27 （11.3 ppm）。有了这样的精度和准确性，现在可以在自然样品中检测到142 /144Nd比率的细微变化，低至3ppm。145Nd/144Nd、148Nd/144Nd和150Nd/144Nd比率的微小差异现在也可以在自然样品中检测到，从而更好地识别地外样品中的核合成异常。对于陆地样品，它允许检测钐的痕迹，以及由于分析问题引起的核场位移效应。特别是，我们证明了一些Sm存在于JNdi-1标准中，并影响其148Nd/144Nd和150Nd/144Nd的比率，因此需要进行系统的干扰校正。通过检测核场位移效应对Nd同位素的存在，我们现在可以防止将142 /144Nd偏差错误地归因于冥古宙期间获得的放射性成因特征的错误解释。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Chemical Geology 地学-地球化学与地球物理

CiteScore

7.20

自引率

10.30%

发文量

374

审稿时长

3.6 months

期刊介绍： Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry. The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry. Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry. The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.