¹⁸⁴Os/¹⁸⁸Os and ¹⁸⁶Os/¹⁸⁸Os measurements by Negative Thermal Ionisation Mass Spectrometry (N-TIMS): Effects of interfering element and mass fractionation co

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• 作者：Ambre Luguet ; Geoff M. Nowell ; D. Graham Pearson
• 关键词：Osmium isotopes ; Pt– ; Os system ; N-TIMS ; Core– ; mantle interaction
• 刊名：Chemical Geology
• 出版年：2008
• 期刊代码：12_00092541
• 类别：ear
• 出版时间：28 February 2008
• 卷：248
• 期：3-4
• 页码：342-362
• 文件大小：960 K

摘要

Precise and accurate measurements of ¹⁸⁶Os/¹⁸⁸Os and ¹⁸⁴Os/¹⁸⁸Os ratios are a key requirement in the search for evidence of interaction between the Earth's core and mantle [e.g., Brandon, A.D., Walker, R.J., 2005. The debate over core–mantle interaction. Earth Planet. Sci. Lett. 232, 211–225] and in understanding nucleosynthetic processes, in particular the P-process, occurring in stars [e.g., Liu, Y., Huang, M., Masuda, A., Inoue, M., 1998. High-precision determination of osmium and rhenium isotope ratios by in-situ oxygen isotope correction using negative thermal ionisation mass spectrometry. Int. J. Mass Spectrom. Ion Process 173, 163–175.; Brandon, A.D., Walker, R.J., Puchtel, I.S., 2006. Platinum–osmium isotope evolution of the Earth's mantle: constraints from chondrites and Os-rich alloys. Geochim. Cosmochim Acta 70, 2093–2103.]. Here we present a detailed study of the effects of polyatomic interferences, mass fractionation and correction procedures that influence and ultimately limit the quality of Os isotope data that can be obtained using the N-TIMS method. Among the polyatomic interferences monitored closely, O isotopic interferences can lead to a 21 ppm deviation of the ¹⁸⁶Os/¹⁸⁸Os depending on the O isotopic composition used for correction. We found that because of the variation of the O isotopic composition within and between analyses, O isotopic composition should be determined in-run.