Menderes masifi’ndeki (Hacýaliler/Çine-Aydýn) granat (Lal Taþý) porfiroblastlarýnýn, Mineralojik-Jeokimyasal ve gemolojik Ýncelenmesi

Antik dönem doða bilimcisi Plinius, Hellenistik ve Roma döneminde yaygýn olarak kullanýlan almandin bileþimli lal taþlarýnýn (Granat) Anadolu'da Karia'da Alabanda (Çine) ve Orthosia'da (Yenipazar) çýkarýldýðýndan bahsetmektedir. Çalýþmaya konu edilen granat örnekleri Hacýaliler (Çine-Aydýn) bölgesinde Menderes Masifine ait orta-yüksek dereceli, gnays ve mikaþist bileþimli metamorfik kayaçlar içerisinde bulunmaktadýr. Boyutlarý 0.5-2 cm arasýnda deðiþen, morumsu-kahverengi renkli ve mat parlaklýk gösteren granat porfiroblastlarý dodekahedron formda kristallenmiþlerdir. Mikroskobik incelemelerinde poikloblast doku gösteren granat mineralleri oldukça kýrýklý bir yapýda olup, bol miktarda kuvars, muskovit ve opak mineral kapanýmlarý içermektedir. Tahribatsýz bir analiz tekniði olan Konfokal Raman spektroskopisi çalýþmalarýna göre granatlarýn 910-912, 349 ve 553-555 cm-1 güçlü olmak üzere toplam 10 farklý Raman titreþimi gösterdikleri ve tipik olarak almandin bileþiminde olduklarý tespit edilmiþtir. Mineral kimyasý sonuçlarýna göre granatlar Alm0.72-0.87 Grs0.07-0.19 Pyr0.02-0.13 Sps0.00-0.02 kimyasal formülüne sahiptirler. Granat – Biyotit jeotermometre hesaplamalarýna göre granatlarýn ortalama 565.3 ± 20.8°C sýcaklýkta, 6.6 kbar basýnç altýnda oluþtuklarý belirlenmiþtir. Hacýaliler granatlarýnýn ortalama kýtasal kabuk çoklu element deðiþim diyagramýnda LIL elementleri (Cs, Rb, Ba, K, Sr, Pb) bakýmýndan fakirleþme gösterdiði belirlenmiþtir. Kondrit’e göre normalize edilmiþ NTE çoklu element deðiþim diyagramýnda granat örneklerinin NTE bakýmýndan zenginleþme gösterdikleri (∑NTE: 192.2-212.1), (La/Sm)N oraný 2.62-2.89, (Sm/Yb)N oraný 0.31-0.38 ve (Eu/Eu*)N oraný 0.41-0.44 arasýnda deðiþtiði belirlenmiþtir. Gemolojik testlere göre granat kristallerinin özgül aðýrlýklarý 3.33 ile 3.64 arasýnda deðiþmekte, kýrýlma indis deðerleri ise 1.81-1.95 civarýndadýr. L*a*b* renk sistemine göre granat kristallerinin renk ortalamasý L*: 46.25 a*: 6.55 b*: 6.60 (morumsu kahverengi) olarak belirlenmiþtir. Mineralojik, jeokimyasal ve gemolojik deðerlendirmeler sonucunda Hacýaliler granat örneklerinin çok evreli metamorfizmaya uðramýþ olmasý ve sonrasýnda geliþen jeolojik süreçlerle (ayrýþma, alterasyon vb.) parlak ve þeffaf olan kristal formlarýný kaybettikleri bu nedenle süstaþý özelliði göstermedikleri deðerlendirilmiþtir. Ayrýca granat örneklerinin NTE içerikleri bakýmýndan önemli bir potansiyele sahip olabilecekleri düþünülmektedir.

Mineralogical-Geochemical and gemological investigations garnet porphyroblasts (Lal Stones) in Menderes massif (Hacýaliler/Çine-Aydýn)

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 Hacýaliler (Çine-Aydýn) 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 Hacýaliler 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 non-destructive 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 Hacýaliler 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.