Mineralogical-Petrographic characteristics of garnet porphyroblasts (Ekinözü-Kahramanmaraş), determination of metamorphism conditions and gemstone potential

Authors : Ufuk Ören, Tamer Koralay

Pages : 1439-1455

Doi:10.65206/pajes.02817

View : 60 | Download : 108

Publication Date : 2025-12-17

Article Type : Research Paper

Abstract :The studied garnet porphyroblasts occur within metamorphic rocks consisting of schists with variable mineralogical compositions in the Ekinözü (Kahramanmaraş) region. The porphyroblasts crystallized in pentagonal dodecahedron forms, ranging in size from 0.5 to 4 cm and exhibit dark red to reddish-black colors with vitreous luster. Microscopic observations reveal that the garnet porphyroblasts display a highly fractured and cracked texture, containing inclusions of quartz, chlorite and opaque minerals such as ilmenite-magnetite. Confocal Raman spectroscopy analyses indicate that the garnet porphyroblasts are of almandine composition. Their chemical structural formulas were determined as Alm0.80-0.88Prp0.07-0.13Grs0.01-0.07Sps0.00-0.05. Garnet-biotite geothermometry calculations suggest that the garnets crystallized under average pressure conditions of ~4.5 kbar at temperatures of 465.4±41.6 °C. Multi-element variation diagrams normalized to the lower and upper continental crust indicate depletion in LIL elements (Sr, K, Rb and Ba), whereas enrichment is observed in HFS elements (Ta, P, Zr, Hf and Y). Chondrite-normalized multi-element diagrams show up to 100-fold enrichment in Rare Earth Elements (REE) (∑REE: 162.1-284.9; (La/Sm)N = 1.65-3.62; (Sm/Yb)N = 0.43-0.67). Enrichment Factor (EF) calculations from chemical analyses highlight the role of Co, Fe, U and Mn elements in color development. These findings are further supported by EPMA data and optical absorption spectroscopy, both of which confirm the predominant presence of Fe+2 ions. Mineralogical, geochemical and gemological investigations indicate that the Ekinözü garnet porphyroblasts formed under greenschist facies metamorphic conditions. Their euhedral crystal morphology, together with their dark red coloration and vitreous luster, suggests that these garnets have potential for use as gemstones in jewelry.
Keywords : Granat porfiroblastları, Raman spektroskopisi, Mineral kimyası, Gemoloji, Süs taşı

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