A new set of standards for in–situ measurement of bromine abundances in natural silicate glasses: Application to SR-XRF, LA-ICP-MS and SIMS techniques

• Published in: Chemical geology Vol. 452; pp. 60 - 70
• Main Authors: Cadoux, Anita, Iacono-Marziano, Giada, Paonita, Antonio, Deloule, Etienne, Aiuppa, Alessandro, Nelson Eby, G., Costa, Michela, Brusca, Lorenzo, Berlo, Kim, Geraki, Kalotina, Mather, Tamsin A., Pyle, David M., Di Carlo, Ida
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-03-2017; Elsevier
• Subjects: Bromine; Earth Sciences; INAA; LA-ICP-MS; Sciences of the Universe; SIMS; SR-XRF; Volcanic glasses; Volcanology; Bromine; LA-ICP-MS; SIMS; Volcanic glasses; SR-XRF; INAA; bromine; volcanic glasses
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2017.01.012

Measuring the low bromine abundances in Earth's materials remains an important challenge in order to constrain the geodynamical cycle of this element. Suitable standard materials are therefore required to establish reliable analytical methods to quantify Br abundances. In this study we characterise 21 Br-doped glasses synthesized from natural volcanic rocks of mafic to silicic compositions, in order to produce a new set of standards for Br analyses using various techniques. The nominal Br contents (amounts of Br loaded in the experimental samples) of 15 of 21 glasses were confirmed within 20% by instrumental neutron activation analysis (INAA). Using this new set of standards, we compare three micro-analytical approaches to measure Br contents in silicate glasses: synchrotron X-ray fluorescence (SR-XRF), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). With SR-XRF, the Br contents of the standard glasses were determined with the highest accuracy (<10% for Br≥10ppm; >25% for Br≤5ppm), and high precision (<10% for Br contents >10ppm; 20–30% for Br≤10ppm). The detection limit was estimated to be <1ppm Br. All those factors combined with a high spatial resolution (5×5μm for the presented measurements), means that SR-XRF is well suited to determine the low Br abundance in natural volcanic glasses (crystal-hosted melt inclusions or matrix glasses of crystallized samples). At its current stage of development, the LA-ICP-MS method allows the measurement of hundreds to thousands ppm Br in silicate glasses with a precision and accuracy generally within 20%. The Br detection limit of this method has not been estimated but its low spatial resolution (90μm) currently prevents its use to characterise natural volcanic glasses, however it is fully appropriate to analyse super liquidus or sparsely phyric, Br-rich experimental charges. Our study shows that SIMS appears to be a promising technique to measure the low Br contents of natural volcanic glasses. Its spatial resolution is relatively good (~15μm) and, similarly to SR-XRF, the detection limit is estimated to be ≤1ppm. Using our new set of standards, the Br contents of two MPI-DING reference glasses containing ≤1.2ppm of Br were reproduced with precision <5% and accuracy <20%. Moreover, SIMS presents the advantage of being a more accessible instrument than SR-XRF and data processing is more straightforward.
•Three sets of bromine-doped silicate glasses have been synthesized from basaltic, andesitic and rhyodacitic volcanic rocks.•The Br contents of the synthetic glasses have been determined by INAA.•These glasses are homogeneous and can be used as standards to quantify Br contents in silicate glasses by micro-analytical techniques.•We present the first Br measurements by SIMS in silicate glasses (the Br-doped glasses and two MPI-DING reference glasses).•Both SIMS and SR-XRF are well suited methods to determine accurately low Br contents (≤10ppm) in natural volcanic glasses.