MGP-1 Plagioclase: A Potential Element and Sr Isotope Reference Material for In Situ Microanalysis

Plagioclase, one of the most common rock-forming minerals, can provide useful information on the crystallisation environment, magmatic evolution and thermal history of host rocks. Owing to matrix effects, trace element and Sr isotope in situ measurements in plagioclase have been hindered by a shortage of reference materials for quality control and method validation. A natural plagioclase sample from Madagascar was evaluated for its feasibility as a reference material for Sr isotope and element determination. Measurement results from EPMA, LA-ICP-MS and LA-MC-ICP-MS indicate that MGP-1 plagioclase is homogeneous at the μm–mm scale with respect to major elements (RSD < 4%), most trace elements (RSD < 15%), and ⁸⁷Sr/⁸⁶Sr ratio (2s = 0.00013). Major and trace elements were also determined using XRF and solution ICP-MS, showing good agreement within 10% from in situ measurement results. The ⁸⁷Sr/⁸⁶Sr ratio obtained by TIMS ranged from 0.703441 to 0.703477, with a mean value of 0.703459 (2s = 0.000028), consistent with the LA-MC-ICP-MS mean value. Reference values and uncertainties for major and trace elements and ⁸⁷Sr/⁸⁶Sr ratio are presented in this study. Consequently, the MGP-1 plagioclase can be used as a reference material for in situ measurement of trace elements and ⁸⁷Sr/⁸⁶Sr ratios, contributing to research on the formation and evolution of micro-zoned plagioclase and host rocks.