Ruichen GAO, , Shiqi WANG, Hao JIANG, Mingcan YANG, Shunhao FU. 0: Petrography and chemical compositions of the clinopyroxene in Jiadan basalts from the Mid-Pacific Mountains and its geological significance. Geological Bulletin of China. DOI: 10.12097/gbc.2024.11.052
Citation:
Ruichen GAO, , Shiqi WANG, Hao JIANG, Mingcan YANG, Shunhao FU. 0: Petrography and chemical compositions of the clinopyroxene in Jiadan basalts from the Mid-Pacific Mountains and its geological significance. Geological Bulletin of China. DOI: 10.12097/gbc.2024.11.052
Ruichen GAO, , Shiqi WANG, Hao JIANG, Mingcan YANG, Shunhao FU. 0: Petrography and chemical compositions of the clinopyroxene in Jiadan basalts from the Mid-Pacific Mountains and its geological significance. Geological Bulletin of China. DOI: 10.12097/gbc.2024.11.052
Citation:
Ruichen GAO, , Shiqi WANG, Hao JIANG, Mingcan YANG, Shunhao FU. 0: Petrography and chemical compositions of the clinopyroxene in Jiadan basalts from the Mid-Pacific Mountains and its geological significance. Geological Bulletin of China. DOI: 10.12097/gbc.2024.11.052
The Jiadan Guyot is an important part of the Mid-Pacific Mountains. The clinopyroxene in its basalts provides valuable insights into the magmatic evolution and formation of oceanic island basalts. This study uses petrographic observations and mineralogical analysis to classify clinopyroxene types and explore basaltic magmatic evolution in the Mid-Pacific Mountains. Clinopyroxene in Jiadan basalts can be divided into four types: Type I exhibits a core-mantle-rim structure; Types II and III have a core-rim structure; and Type IV is homogeneous without zones. The cores of Type I and III clinopyroxene (with Mg# values >85) are antecrysts, while others are autocrysts. Mineralogical analysis reveals that clinopyroxene cores show the highest Mg# values and Cr content, which decrease towards the rim, while Al2O3, TiO2, and ΣREE levels increase. This pattern indicates ongoing evolution of the primitive magma. The highest crystallization temperatures and pressures (~1170 °C and ~3.50 kbar) are observed in the cores of Type I and III clinopyroxene with Mg# >85. Lower temperatures and pressures (~1070 °C and ~0.72 kbar) are found in the mantles of Type I, cores of Type II and III (with Mg# <85), and Type IV clinopyroxene, with further decreases at the rims. In summary, clinopyroxene formation in Jiadan basalts reflects a sequence of magmatic evolution stages, including a deep crystallization stage (~11 km depth), a shallow magma chamber stage (~2.5 km depth), and a magma conduit stage (~0.4 km depth).
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