Micro-Inclusion Composition and Raman Spectral Characteristics of
Pyroxene From Mingxi, Fujian
ZHOU Hui-wei1, ZHANG Lu2, YANG Li-yi3, XU Shuang3, SHEN Hong-tao4, LIU Yun-gui5, 6, 7, 8, SONG Yan-jun5, 6, 7, 8*
1. Faculty of Earth Sciences, Hebei GEO University, Shijiazhuang 050031，China
2. Hebei Geo-Environment Monitoring, Shijiazhuang 050031，China
3. Guoye Shandong Bureau Group Geological Experiment Testing Technology Co., Ltd.，Jinan 250000，China
4. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences(Wuhan), Wuhan 430074，China
5. Faculty of Gemmology and Materials, Hebei GEO University, Shijiazhuang 050031，China
6. Gemstone Testing Center, Hebei GEO University, Shijiazhuang 050031，China
7. Engineering Research Center for Silicate Solid Waste Resource Utilization of Hebei Province, Shijiazhuang 050031，China
8. Hebei Key Laboratory of Green Development of Rock and Mineral Materials, Shijiazhuang 050031，China
Abstract：Pyroxene megacrysts are common minerals in Cenozoic alkaline basalt bodies in the eastern region of China. These pyroxenes and their internal inclusions provide important evidence for studying the composition of deep-mantle materials and deep-seated processes in eastern China. This study employs electron probe microanalysis (EPMA) and laser Raman spectroscopy to investigate the chemical composition and Raman spectral characteristics of pyroxene megacrysts and their microscopic inclusions in basalt bodies from the Mingxi area, Fujian Province. The results indicate that the Mingxi pyroxenes are augites, characterized by well-developed fractures and relatively high Ca and Mg contents. Their calculated chemical formula is (Ca0.66～0.68Na0.04～0.05Mg0.27～0.30)(Al0.25～0.26Fe2+0.18～0.21Fe3+0.04Ti0.02～0.03Mg0.48～0.50）[(Si1.86～1.92Al0.08～0.14)O6], with Raman characteristic peaks located at 1 008, 670, 545, 396, 338, and 232 cm-1. The pyroxenes contain abundant linear, dotted, or dashed metallic mineral inclusions, primarily composed of pyrrhotite and hematite mixtures, while fractures exhibit goethite impregnation. Among these, pyrrhotite is a mantle-derived inclusion with a chemical formula of Fe（0.81~0.88）S, whereas hematite and goethite are its later oxidation and hydration products. The fluid inclusions in Mingxi pyroxenes are mainly CO2, with a Fermi resonance doublet peak separation (Δσ) of 104.643 cm-1 in Raman spectroscopy. Based on the linear relationship between the Fermi resonance doublet and gas density, as well as the ideal gas equation of state, the formation depth is estimated to be greater than 72 km. The findings of this study provide valuable data for further research on the formation of basalt bodies and deep-seated processes in southeastern China.
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