LA-ICP-MS of magnetite: Methods and reference materials
Magnetite (Fe 3 O 4 ) is a common accessory mineral in many geologic settings. Its variable geochemistry makes it a powerful petrogenetic indicator . Electron microprobe ( EMPA ) analyses are commonly used to examine major and minor element contents in magnetite . Laser ablation ICP-MS ( LA-ICP-MS ) is applicable to trace element analyses of magnetite but has not been widely employed to examine compositional variations. We tested the applicability of the NIST SRM 610, the USGS GSE-1G, and the NIST SRM 2782 reference materials (RMs) as external standards and developed a reliable method for LA-ICP-MS analysis of magnetite . LA-ICP-MS analyses were carried out on well characterized magnetite samples with a 193 nm, Excimer, ArF LA system. Although matrix -matched RMs are sometimes important for calibration and normalization of LA-ICP-MS data, we demonstrate that glass RMs can produce accurate results for LA-ICP-MS analyses of magnetite . Cross-comparison between the NIST SRM 610 and USGS GSE-1G indicates good agreement for magnetite minor and trace element data calibrated with either of these RMs. Many elements show a sufficiently good match between the LA-ICP-MS and the EMPA data; for example, Ti and V show a close to linear relationship with correlation coefficients, R 2 of 0.79 and 0.85 respectively.