Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in
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Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in Quartz-Hosted Fluid Inclusions Sara Ladenburgera, Benjamin F. Waltera, Michael A. W. Marksa, *, and Gregor Markla aFachbereich
Geowissenschaften, Universität Tübingen, Tübingen, 72074 Germany *e-mail: [email protected]
Received October 17, 2018; revised March 18, 2019; accepted May 22, 2020
Abstract—The crush-leach technique is a frequently used method to determine the bulk composition of fluid inclusions trapped in a range of geological samples. We present a modified crush-leach technique combining ion chromatography (IC) and total reflection X-ray fluorescence spectroscopy (TXRF) which allows to determine a range of major, minor and trace elements out of one leachate. To date, trace element detection by means of TXRF is barely used in geosciences, although it combines the advantages of low to very low detection limits (μg/L to ng/L range), small sample amount needed (μL-range) and a fast and inexpensive analytical procedure. Previously described problems of adsorption of polyvalent cations at sample surfaces have been overcome by using acidified water as a leachate. Instead, it has been demonstrated that, for example, the syringe filter type used for IC measurements influences contamination and/or adsorption for a number of elements. The proposed method combination was evaluated for accuracy, reproducibility and system blanks and subsequently applied to quartz samples from hydrothermal vein deposits of the Schwarzwald ore district, SW Germany. Keywords: crush-leach analysis, fluid inclusion, adsorption, contamination, syringe filter, ion chromatography, total reflection X-ray fluorescence DOI: 10.1134/S106193482011009X
Fluid inclusions in minerals represent relics of geological fluids trapped during their growth (primary inclusions) or during healing of later formed fractures (secondary inclusions). Depending on the type of fluid inclusion (primary or secondary) and the nature of the investigated sample, the composition of fluid inclusions records the physical and chemical properties during sedimentary, diagenetic, metamorphic, magmatic or hydrothermal processes [1–4]. Knowledge of the chemical composition of such fluids is important for the improvement of geochemical models for crustal fluid processes and to understand transport of metals in crustal fl uids and fluid−rock interaction in detail [5–9]. Fluid inclusion petrography and microthermometry allow for the identification of physical properties of fluids, their gas composition and salinity [10–13], but for determining their detailed chemical composition (including minor and trace element concentrations and element ratios, such as Na/K or Cl/Br) more precise methods are needed [14–17]. The crush-leach technique is a method where fluid inclusions of a bulk sample are opened by mechanical crushing or thermal decrepitation and are subsequently leached with ultra-pure water [5]. The extracted solution can then be analyzed
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