Three Spodumene Reference Materials for Oxygen Isotope Measurement by Ion Microprobe

This study reports on the development of three spodumene reference materials referred to as Curtin University (CU) Tri‐1, Kun‐A‐1 and MG‐1 for calibrating the instrumental mass fractionation for oxygen isotope measurement by secondary ionisation mass spectrometry (SIMS). Millimetre‐sized fragments were prepared from gem‐quality spodumene crystals with chemical compositions close to the ideal spodumene end member (LiAlSi 2 O 6 ). From these fragments, six subsamples were extracted for laser fluorination isotope ratio mass spectrometry (LF‐IRMS) to determine the bulk oxygen isotope ratio of the three materials and confirm their homogeneity on the mg scale. The bulk δ 18 O (VSMOW) values are 11.29 ± 0.04‰, 9.12 ± 0.10‰ and 15.13 ± 0.08‰ (all 2SE, standard error of the mean) for materials Tri‐1, Kun‐A‐1 and MG‐1, respectively. A random selection of twenty or more fragments from each material was subjected to SIMS analysis. Repeatability of SIMS δ 18 O measurements was at most 0.24‰ (2 s ), indicating oxygen isotopic homogeneity on the ng scale. Crystal orientation effects potentially affecting SIMS analysis were systematically evaluated and found to be absent at levels equivalent to the repeatability of the method. Applications of the new materials lie mainly in furthering research on pegmatite formation and tracing of raw materials by providing the means for accurate, in situ oxygen isotope measurement in spodumene.