Özet:

Ancient period naturalist Plinius referred that almandine composition Lal Stones (Granat) which had been widely used in the Hellenistic and Roman periods, were extracted from Alabanda (Çine) and Orthosia (Yenipazar) in Karia in Anatolia. The garnet samples, which are the subject of this study, are found in the middle-high grade, gneiss, and mica-schist in the Menderes Massif in Hacıaliler (Çine-Aydın) region. Purplish-brown and matt garnet porphyroblasts, varying between 0.5-2 cm in size, have crystallized in dodecahedron form. Garnet minerals, display poikloblastic texture in microscopic examinations, are in a highly fractured structure and contain plenty of quartz, muscovite, and opaque mineral inclusions. In line with a non-destructive analysis technique, Confocal Raman Spectroscopy studies, it has been determined that garnets present a total of 10 different Raman vibrations, 910-912, 349 and 553-555 cm-1 strong, and are typically in almandine composition. According to the results of mineral chemistry, garnets have the chemical formula of Alm0.72-0.87 Grs0.07-0.19 Pyr0.02-0.13 Sps0.00-0.02. In accordance with garnet-biotite geothermometer calculations, it was determined that garnets are formed at an average temperature of 565.3±20.8 °C and under the pressure of 6.6 kbar. It was concluded that Hacıaliler garnets demonstrated depletion in terms of LIL elements (Cs, Rb, Ba, K, Sr, Pb) in the average continental crust (MCC) multi-element variation diagram. It was discovered that garnet samples demonstrated enrichment in terms of REE (∑REE: 192.2-212.1), (La/Sm)N ratio 2.62-2.89, (Sm/Yb)N ratio 0.31-0.38 and (Eu) /Eu*)N ratio vary between 0.41-0.44 in REE multi-element variation diagram normalized to chondrite. According to the nondestructive gemological tests, the specific gravity of garnet crystals varies between 3.33 and 3.64, and the refractive index values were found to be around 1.80-1.81. According to the L*a*b* color system, the color average of garnet crystals was determined to be as L*: 46.25 a*: 6.55 b*: 6.60 (purplish brown). As a result of mineralogical, geochemical, and gemological evaluations, it has been concluded that Hacıaliler garnet samples have undergone multi-stage metamorphism and have lost their bright and transparent crystal forms through the subsequent geological processes (weathering, alteration, etc.); therefore, they do not present the characteristics of gemstones. In addition, it is thought that garnet samples may have an important potential in terms of their REE contents.

Anahtar Kelimeler: