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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
Author(s)
Language
English
Obiettivo Specifico
2V. Dinamiche di unrest e scenari pre-eruttivi
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/452(2017)
ISSN
0009-2541
Electronic ISSN
1872-6836
Publisher
Elsevier Science Limited
Pages (printed)
60-70
Issued date
2017
Keywords
Abstract
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 newset 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 (b10% for Br ≥ 10 ppm; N25% for Br ≤ 5 ppm), and high precision
(b10% for Br contents N10 ppm; 20–30% for Br ≤ 10 ppm). The detection limit was estimated to be b1 ppm Br.
All those factors combined with a high spatial resolution (5 × 5 μm for the presented measurements), means
that SR-XRF iswell suited to determine the lowBr 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
(90 μm) 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 lowBr contents of natural volcanic glasses. Its spatial resolution is relatively
good (~15 μm) and, similarly to SR-XRF, the detection limit is estimated to be ≤ 1 ppm. Using our new set of standards,
the Br contents of two MPI-DING reference glasses containing ≤ 1.2 ppm of Br were reproduced with precision
b5% and accuracy b20%. Moreover, SIMS presents the advantage of being a more accessible instrument
than SR-XRF and data processing is more straightforward.
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 newset 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 (b10% for Br ≥ 10 ppm; N25% for Br ≤ 5 ppm), and high precision
(b10% for Br contents N10 ppm; 20–30% for Br ≤ 10 ppm). The detection limit was estimated to be b1 ppm Br.
All those factors combined with a high spatial resolution (5 × 5 μm for the presented measurements), means
that SR-XRF iswell suited to determine the lowBr 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
(90 μm) 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 lowBr contents of natural volcanic glasses. Its spatial resolution is relatively
good (~15 μm) and, similarly to SR-XRF, the detection limit is estimated to be ≤ 1 ppm. Using our new set of standards,
the Br contents of two MPI-DING reference glasses containing ≤ 1.2 ppm of Br were reproduced with precision
b5% and accuracy b20%. Moreover, SIMS presents the advantage of being a more accessible instrument
than SR-XRF and data processing is more straightforward.
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