Simultaneous determination of the oxygen isotope ratio and vola-tile composition of apatite with high lateral resolution via nano-secondary-ion mass spectrometry

Abstract

Apatite is commonly used as a tracer in Earth and planetary sciences by leveraging its oxygen isotopes and volatile compo-sitions to elucidate the derivation and evolution of magma and geological fluids. While secondary-ion mass spectrometry has proven effective in determining these compositions in apatite, the challenge lies in its relatively large spot size (＞20μm), and obtaining O isotope and volatile data from different grains or domains. In addition, the sequential analysis of volatiles is both time-consuming and constrained by limited data, leading to increased uncertainties in subsequent elemental analysis. This hinders robust interpretations for geological events and the determination of smaller-grained apatite. In this study, we propose a high lateral resolution (~7μm）method for the simultaneous analysis of the O isotope ratio and volatile (OH, F, Cl, and S) composition of apatite. The analysis of the eight apatite standards using this method yields results that are consistent with literature values, demonstrating its reliability and robustness. This innovative approach stands out not only for its high lateral resolution but also for its enhanced data robustness, laying a solid foundation for further scientific investigation and analysis.