---

Importance of clinopyroxene mineral chemistry as a potential petrogenetic indicator: A case study from gabbroic intrusives from Western Iron Ore Group, Singhbhum Craton, Eastern India.

Paul M, Ghosh B, Morishita T, Tamura A, Ray J, Manikyamba C, Patel SC.

JOURNAL OF EARTH SYSTEM SCIENCE

http://dx.doi.org/10.1007/s12040-025-02528-y 

Pyroxenes are considered a key petrogenetic indicator, as their chemical composition and crystal structure fingerprint the temperature, pressure, and magma conditions during rock formation, while their zoning/exsolution textures record evolving crystallization changes, making them further useful for exploring Ni-Cu-(PGE) deposits. This study evaluates the nature of magma evolution and subsequent differentiation of Paleoarchean gabbroic rocks from parts of the Western Iron Ore Group of Singhbhum Craton, using the major and trace element compositions of clinopyroxenes. Their chemical systematics indicate subalkaline/tholeiitic parental magma, while high Fe2+/(Fe2++Fe3+) and Ca-rich compositions, along with high AlIV/AlVI ratios suggest low-pressure crystallization in a subduction-related arc setting. Trace element patterns, with depletions in Nb, Ta, Ti, LREE and HREE enrichment indicate the significant role of fluid invasion during petrogenesis, as supported by petrographic evidences such as saussuritized plagioclase and tremolite rims. These findings emphasize fluid-driven magma evolution and provide wider implications on understanding the evolution of the proto-crust during the early growth of shield areas.

BSE image showing a large clinopyroxene (Cpx) phenocryst with a characteristic rim (Cpxrm), along with saussuritized plagioclase (Pls) and ilmenite (Ilm) grains. Tectonic discrimination F1 vs. F2 plot depicting a subduction-related affinity of parent magma.

---