An isotope ratio mass spectrometry-based method for hydrogen isotopic analysis in sub-microliter volumes of water: Application for multi-isotope investigations of gases extracted from fluid inclusions

Alexei Ivanovich Buikin; Olga Vitalievna Kuznetsova; Tatiana Alexeevna Velivetskaya; Vyacheslav Sergeevich Sevastyanov; Alexander Vasilievich Ignatiev

doi:10.1002/rcm.8923

An isotope ratio mass spectrometry-based method for hydrogen isotopic analysis in sub-microliter volumes of water: Application for multi-isotope investigations of gases extracted from fluid inclusions

Rapid Commun Mass Spectrom. 2020 Nov 30;34(22):e8923. doi: 10.1002/rcm.8923.

Authors

Alexei Ivanovich Buikin¹, Olga Vitalievna Kuznetsova¹, Tatiana Alexeevna Velivetskaya², Vyacheslav Sergeevich Sevastyanov¹, Alexander Vasilievich Ignatiev²

Affiliations

¹ Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Kosygin str. 19, Moscow, 119991, Russia.
² Far East Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, Prospect 100-letya Vladivostoku 159, Vladivostok, 690022, Russia.

PMID: 32779244
DOI: 10.1002/rcm.8923

Abstract

Rationale: The study of multi-isotope systematics of fluid inclusions is of great importance for understanding of the sources and evolution of fluid phases in mantle rocks and ore deposits. The most appropriate technique for such investigations is a (stepwise) crushing method that is widely used for noble gases and nitrogen. However, because of the possible influence of mechanochemical reactions and back sorption, analyses of the isotope composition of water extracted by crushing from fluid inclusions are challenging.

Methods: An isotope ratio mass spectrometry (IRMS)-based method for hydrogen (and oxygen) isotopic analysis in sub-microliter volumes of water extracted from fluid inclusions by crushing is presented. The verification of the possible influence of adsorption processes and mechanochemical reactions on the results of isotope analysis was performed for the first time. For that a series of parallel analyses of hydrogen isotopic ratios from water inclusions in quartz applying physically different extraction methods (crushing and thermodecrepitation) was conducted.

Results: Four series of quartz aliquots were analyzed: three series extracting water by crushing (two series for δ² H values and one for δ¹⁸ O values) and one by thermodecrepitation. The mean value for the crushing results is δ² H = -85.3 ± 3.6 ‰ (1σ, n = 11), which coincides well with the thermodecrepitation data (-86.3 ± 2.0 ‰, 1σ, n = 5), suggesting that our methodological approach allows the influence of back sorption or mechanochemical reactions during the crushing experiment to be minimized. The reproducibility of the oxygen isotopic ratios is ±0.9 ‰ (1σ, n = 5).

Conclusions: The conducted experiments have shown that the influence of back sorption or mechanochemical reactions during crushing on isotopic results is not crucial for our method. The developed IRMS-based method for hydrogen (and oxygen) isotopic analysis in sub-microliter volumes of water is well applicable for multi-isotope investigations of gases extracted from fluid inclusions. As an application a well-defined ⁴⁰ Ar/³⁶ Ar-δ² H correlation in mantle rocks is presented for the first time.