黄铁矿中硫同位素的LA—MC—ICP—MS分析方法研究

Study on LA MC ICP MS Analysis Method for Sulfur Isotopes in Pyrite

摘要:

硫元素普遍存在于自然界中，且硫同位素在各大地质储库中分馏显著，已经成为指示地质过程和生物演化过程的重要地球化学示踪剂。尤其是在成矿过程研究中，硫化物的硫同位素组成对反映成矿物质来源具有重要指示意义。微区原位分析技术可以直接作用于矿物，获得微米尺度的同位素组成信息，在矿床形成的精细化研究中具有极大的应用前景。联用激光剥蚀系统（LA）和高精度多接收电感耦合等离子体质谱仪（MCICPMS），在低频率（2 Hz）、较高能量密度（3~5 J/cm2）的激光条件下，引入少量氮气并使用Jet和X锥组合，切换中分辨模式实现了黄铁矿微区原位（32 μm）硫同位素组成的准确、高精度分析。黄铁矿参考物质PPP1的测试值与前人的文献发表值在误差范围内完全一致，δ34S的平均单点分析精度为0.015‰（2 RSE），长期外部重现性为0.26‰（2 SD）。

Abstract:

Sulfur is widely distributed in nature. Moreover, sulfur isotopes are significantly fractionated in various geological reservoirs and have become important geochemical tracers for indicating geological and biological evolution processes. Especially in the study of mineralization processes, the sulfur isotope composition of sulfides has important indicative significance for reflecting the source of ore-forming materials. Micro in-situ analysis technology can directly act on minerals to obtain microscale isotopic composition information, and has great application prospects in the fine research of ore deposit formation. By combining a laser ablation system (LA) with a high-precision multi receiver inductively coupled plasma mass spectrometer (MC ICP MS), a small amount of nitrogen gas was introduced under low frequency (2 Hz) and high energy density (3~5 J/cm2) laser conditions, and a combination of Jet and X-cone was used to achieve in situ (32%) of pyrite micro zones by switching medium resolution modes μ m) Accurate and high-precision analysis of sulfur isotope composition. The test values of the reference substance PPP 1 for pyrite are completely consistent with the published values in previous literature within the error range. The average single point analysis accuracy of δ34S is 0.015 ‰ (2 RSE), and the long-term external reproducibility is 0.26‰ (2 SD).