Magnesium isotope analysis of olivine and pyroxene by SIMS: Evaluation of matrix effects

摘要: Abstract The performance of multi-collector secondary ion mass spectrometry (MC-SIMS) for Mg isotope ratio analysis was evaluated using 17 olivine and 5 pyroxene reference materials (RMs). composition these RMs accurately precisely determined by inductively coupled plasma (MC-ICP-MS), measured ratios were used to evaluate SIMS instrumental bias as a function the forsterite (Fo) content olivine. magnitude matrix effects ~3‰ in δ25Mg, are complex Fo content, that ranged from Fo59.3 Fo100. In addition effects, Si+ yields Mg+/Si+ varied RMs. For example, ~33%. Based on observations, we propose correction procedures combination Using this method, accuracy δ25Mg analyses is 0.3‰, except with Fo86–88 where biases change dramatically making it more difficult assess measurements over narrow range content. Five (3 orthopyroxenes 2 clinopyroxenes) show smaller ranges (~1.4‰ δ25Mg) compared 3 orthopyroxene do not define linear relationship respect enstatite (En) En85.5–96.3. clinopyroxene have similar En wollastonite (Wo) contents but values differ 0.5‰ relative their MC-ICP-MS. These results indicate additional factors (e.g., minor element abundances) likely contribute fractionation. order better correct various chemical compositions known needed.