Investigation of the Geological, Geochemical and Gemological Features of Diaspore Formations on the Southwestern Side of the Menderes Massif (Bafa Lake - Milas)

Abstract

Interest in gemstones, which have been used as symbols of beauty, wealth and status since prehistoric times, has increased in recent years and taken an important place in many countries. The Menderes Massif is the most important area where bauxite deposits are observed in Turkey. Gemstone quality diaspore crystals are formed only in these deposits. In this study, the mineralogical, geochemical and gemological features of the diaspore formations on the south-western side of the Menderes Massif (Bafa Lake - Milas) were investigated. In field studies carried out in the study area, diaspore crystals were found in the Pinarcik region, located between Bafa Lake and Milas, within metabauxite formations together with chloritoid and muscovite, and in some places were encountered in altered zones close to the metabauxite limestone contact. As a result of petrographic analyses of the wallrock samples, grano-lepidoblastic textured muscovite-quartzschist, quartz-phyllite, mica-quartzschist and lepidoblastic textured phyllite, and nematoblastic textured greenschist-chlorite-epidote fels rocks were identified. To evaluate the main oxide, traces and rare earth elements on the 28 collected samples, Al2O3-SiO2-Fe2O3 triangular variation was used. According to the classification, the bauxite samples were determined to be in the ferric bauxite and bauxite areas. As a result of SEM imaging and EDS analyses performed on the samples, it was determined that the samples mainly contained O, Al and Si. K, Na, Fe, Ca and Mg were also found close to these elements. Using Raman Spectroscopy, in the light of matching values obtained from the microscope's own database, it was seen that the samples taken from Pinarcik (PI) region were diaspore, and brucite (Mg(OH)(2))) and ugillite (Ca-3(Ti, Al, Zr)(9)O(2)0) minerals were also detected. In addition, FTIR analysis was performed on 4 samples taken from Pinarcik (PI) region and according to the results of their analysis, it was seen that the samples were compatible with standard wavelength references. It was scientifically proven that the samples collected from the region and subjected to facet processing are gemstone quality diaspore crystals with various color variations. This study will make an important contribution to understanding the properties of the gemstone quality diaspore mineral, its formation, and finding similar formations in the region.