In situ Lithium and Boron isotope determinations in mica, pyroxene, and serpentine by LA-MC-ICP-MS
| Type | Article | ||||||||||||
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| Date | 2015-09 | ||||||||||||
| Language | English | ||||||||||||
| Author(s) | Marti Celine1, Ponzevera Emmanuel 2, 3, Harlow George1 |
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| Affiliation(s) | 1 : Amer Museum Nat Hist, Dept Earth & Planetary Sci, New York, NY 10024 USA. 2 : Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. 3 : Inst Carnot Ifremer EDROME, Dept Ressources Phys & Ecosyst Fond Mer REM, Lab Geochim Metallogenie, F-29280 Plouzane, France. |
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| Source | Chemical Geology (0009-2541) (Elsevier Science Bv), 2015-09 , Vol. 412 , P. 107-116 | ||||||||||||
| DOI | 10.1016/j.chemgeo.2015.07.022 | ||||||||||||
| WOS© Times Cited | 37 | ||||||||||||
| Keyword(s) | Boron isotopes, Lithium isotopes, LA-MC-ICP-MS, Subduction zone related silicates | ||||||||||||
| Abstract | Boron and Li are light, incompatible elements that preferentially partition into the liquid phase, whether melt or aqueous fluid, and thus are useful for tracking fluid-related processes in rocks. Most of the Li isotopic data presently available on subduction-related rocks are from whole-rock analyses; and the B isotopic analyses of subduction material have been carried out either on whole-rocks or in-situ on an accessory phase, such as tourmaline. The new method presented here couples an ESI New Wave UP-193-FX ArF* (193 nm) excimer laser-ablation microscope with a Neptune Plus (Thermo Scientific) MC-ICP-MS aiming to measure both Li and B isotopes in situ with good spatial resolution (metamorphic minerals are commonly chemically zoned, and whole-rock analyses lose this detail). The data thus obtained are compared with SIMS analyses on the same mineral samples for B, and with MC-ICP-MS analyses on whole-rock or mineral separates from the same sample for Li. Additionally, data acquired on tourmaline standards were compared to SIMS values. The results show that for B concentrations above 5 μg/g, the data obtained by LA-MC-ICP-MS and by SIMS are identical within error, for mica (phengitic muscovite), pyroxene (jadeite), serpentine (antigorite), and tourmaline. For Li concentrations above 10 μg/g, the data obtained by LA-MC-ICP-MS and by MC-ICP-MS are also identical, within error, for mica (phengitic muscovite), and pyroxene (jadeite). However, analyses of tourmaline standards have shown significant differences with reference values, so LA-MC-ICP-MS does not yet appear to be an appropriate method to analyze Li isotopes in tourmalines. Thus, LA-MC-ICP-MS is a suitable method to measure Li and B isotopes with good spatial resolution in major rock-forming silicates from subduction-related rocks where concentrations exceed 10 μg/g and 5 μg/g, respectively, with an error on individual measurements equal to or less than previously used methods, but obtainable in a significantly shorter amount of time. The external reproducibility is ± 2.88 to 3.31 ‰ for B and ± 1.50 to 1.75 for Li, which is lower than or equal to the variations encountered within a given chemically zoned sample (up to 10 ‰ of variation within a given natural sample). | ||||||||||||
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