Inter‐laboratory Characterisation of Apatite Reference Materials for Chlorine Isotope Analysis. Issue 1 (25th December 2020)

• Record Type: Journal Article
• Authors: Wudarska, Alicja; Słaby, Ewa; Wiedenbeck, Michael; Barnes, Jaime D.; Bonifacie, Magali; Sturchio, Neil C.; Bardoux, Gérard; Couffignal, Frédéric; Glodny, Johannes; Heraty, Linnea; John, Timm; Kusebauch, Christof; Mayanna, Sathish; Wilke, Franziska D. H.; Deput, Ewa
• Is Part Of: Geostandards and geoanalytical research. Volume 45:Issue 1(2021)
• Page Start: 121
• Page End: 142
• Publication Date: 2020-12-25
• Subjects: chlorine isotopes -- apatite -- matrix effect -- crystal orientation effect -- secondary ion mass spectrometry; Analytical geochemistry -- Periodicals; Géochimie analytique -- Périodiques; 551.9
• DOI: 10.1111/ggr.12366
• Languages: English
• ISSNs: 1639-4488

Abstract

Abstract : Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca10 (PO4 )6 (F, Cl, OH)2 solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for 37 Cl/ 35 Cl homogeneity using SIMS followed by δ 37 Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1 s ) for the five samples with > 0.5 % m / m Cl and ± 0.19‰ (1 s ) for the low Cl abundance material (0.27% m / m ). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean 37 Cl/ 35 Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ 37 ClSMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 10 3 δ 37 ClSMOC values between +0.09 and +0.42 and in all cases with 1 s ≤ ± 0.25. Key Points: Six apatite reference materials having various Cl mass fractions were characterised for chlorine isotope ratios by SIMS and three GS‐IRMS laboratories. A small, but significant, crystal orientation effect was recorded by SIMS analyses. Correlation of instrumental mass fractionation factor with Cl mass fraction is visible along the apatite solid solution series.