High-Precision Determination of Os/Os and Os/Os Isotope Ratios via an Antimony Fire Assay and Multi-collector ICP-MS.

Journal: Analytical chemistry
Published Date: Apr 2, 2025

Abstract

The Pt-Os and Re-Os isotopic systems are powerful tools for researching the evolution of the Earth and the Solar System. However, high-precision Os/Os analyses remain challenging. In this study, the preconcentration of osmium (Os) has been achieved by the adoption and decomposition of large amounts of geological materials (over 20 g) with the novel use of the antimony (Sb) fire assay. This enables high-precision Os/Os and Os/Os ratio measurements. The total procedural blanks of Os have been reduced to less than 10 pg for samples of 20 g through the purification procedures for fire assay collector SbO and the use of quartz crucibles. This study also applies multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) for the Os isotope compositions, which is simple and fast and saves the complex polyatomic interferences and oxygen corrections of the traditional negative thermal ionization mass spectrometry (N-TIMS) method. Three Os standard solutions (DROsS, GSB, and HPS) and six rock reference materials were measured with this analytical protocol. The Os/Os and Os/Os ratios of the DROsS are consistent with previously published values within errors including precision and accuracy. Repeated measurements of the DROsS Os standard solution on MC-ICPMS exhibit fine external reproducibility of better than 53 ppm (2 RSD) for Os/Os, which is sufficient to identify subtle Os/Os variations of geological samples. This study is the first to report the Os/Os and Os/Os ratios of GSB and HPS, which are consistent with the N-TIMS values. Furthermore, the Os/Os and Os/Os ratios of six geological reference materials are in good agreement with N-TIMS values, and the results of WPR-1a and GPt-5 are within measurement uncertainty of the previously published N-TIMS results, confirming the validity of our new analytical procedure for the accurate determination of Os/Os and Os/Os ratios of geological samples.

Authors

  • Hou-Yin Bao
    State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
  • Jie Li
    Guangdong-Hong Kong-Macao Greater Bay Area Artificial Intelligence Application Technology Research Institute, Shenzhen Polytechnic University, Shenzhen, China.
  • Wen-Shan Ni
    Zhengzhou Institute of Multipurpose Utilization of Mineral Resources, CAGS, Zhengzhou 450006, P. R. China.
  • Tian-Tian Wang
    Zhengzhou Institute of Multipurpose Utilization of Mineral Resources, CAGS, Zhengzhou 450006, P. R. China.
  • Neng-Ping Shen
    State Key Laboratory for Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
  • Gao-Bin Chu
    Guangzhou Tuoyan Analytical Technology Co., Ltd., Guangzhou 510640, China.
  • Jin-Gao Liu
    China University of Geosciences, Beijing 10083, China.
  • Jun-Jie Liu
    School of Earth Sciences, Sun Yat-sen University, Guangzhou 519080, Guangdong, China.
  • Ji-Feng Xu
    China University of Geosciences, Beijing 10083, China.

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