Raman spectroscopic characteristics of melanite bearing foid syenites: Yozgat intrusive complex

The foid bearing syenites within the Yozgat Intrusive Complex (YIC), have coarse crystalline, euhedral, dark-black coloured in hand specimen melanite type garnet. They are mainly crop out in Sivritepe, Gedikhasanlı, Mükremin, Karlı hills and Çağlayan vicinity. Foid bearing syenites generally are in the composition of pyroxene syenite, foid syenite, melanite bearing foid syenite, foid syenite porphyry and pyroxene bearing foid syenite porphyry. The scope of this study, is to use the Raman spectra of melanites of the foid syenites to evaluate their significant behavior in the crystallization process of the unit. Melanites are represent the member of the black andradite type of the garnet group. Melanite, is crystallized from the silica undersaturated magma with the Ca3(Fe3+,Ti)2(SiO4)3 chemical formula. Melanites exhibit clear with high spectrum in Raman spectroscopic determinations due to the silicate structure form and their high symmetrical habit within the crystal systems. The melanites are dark brown in color, euhedral shape, with high optical relief and are isotropic under the polarizing microscope. Raman spectra of melanites are identical with the andradite in composition and generally show Raman shift peaks in the range of 170-1000 cm-1. The melanite has 13 spectra in the total, of the 12 spectra of these spectra are asymmetrical and only one spectra has symmetrical character. Three groups of Raman spectra of the melanitetype are identical with the andradites Raman spectra. These are distributed as 371 cm-1, 522 cm-1 and 879 cm-1 respectively. The Raman spectra of the melanites are obtained in two main regions: (a) external vibration below 400 cm-1 and (b) internal vibration above 400 cm-1. The first part of the external vibration up to 400 cm-1 is related to SiO4 tetrahedra and divalent cations. The internal vibration of these garnets belongs to the SiO4 and their spectra are wavenumber ranges of 400-1050 cm-1. Si-O bending modes are observed in the spectral region between 400 and 600 cm-1, and Si-O stretching modes are observed in the spectral region between 700 and 1050 cm-1. The compositional spectra and vibrational modes of the melanites in the YIC show that the crystallization and differentiation processes have been affected by the interaction of different sources of the components rather than the pure main silica undersaturated magma during their crystallization

Principles of raman spectroscopy and their uses in the determination of the minerals

Minerallerin ayrıntılı olarak adlandırmaları ve tanımlamaları ince kesit üzerinde polarizan mikroskop yardımı ile ve toz hale getirilerek X-Işını Kırınımı (XRD) yöntemi ile yapılabilmektedir. Her iki yöntemde mineraller üzerinde tahribat yapılmakta ve ciddi bir bilgi birikimi ve deneyim gerektirmektedir. Raman spektroskopisinde örnek üzerinde herhangi bir tahribat yapmadan, mineral üzerine gönderilerek molekül ile etkileşime giren ışığın dalga boyuna göre saçılan ışığın dalga boyundaki farklar sonucu oluşan spektrumlar, mineralin kimliğini yansıtabilmektedir. Her mineralin moleküler bileşim farklılığından oluşan spektrumlar yardımıyla mineral içerisindeki değişimler ölçülebilmektedir. Böylece mineral adlandırmanın yanında taze ve bozunmuş mineral farklılıkları da bu yöntem ile ayırt edilmektedir. Bu çalışmada Raman spektroskopi yöntemini kullanarak plajiyoklaz, ortoklaz, anortoklaz, biyotit, filogopit ve granat minerallerinin Raman spektroskopik tanımlanmaları yapılmış ve oluştukları kayanın kökeni hakkında yorumlar yapılmıştır. Böylece minerallerin tahribatsız analiz yöntemi ile türlerinin tespiti örneklerle ortaya konulmuştur.The detailed nomenclature and descriptions of the minerals can be made with the aid of a polarizing microscope on the thin section and by powdering with the X-Ray Diffraction (XRD) method. In both methods, minerals are damaged and require serious knowledge and experience. In Raman spectroscopy without any destruction of the sample, the spectra formed as a result of differences in the wavelength of the scattered light compared to the wavelength of the light that interacts with the molecule by being sent on the mineral can reflect the identity of the mineral. The spectra, which consist of the molecular composition difference of each mineral, can also reflect the changes of the measured mineral. Furthermore, in addition to mineral naming, fresh and altered mineral differences are also distinguished by this method. In this study, Raman spectroscopic definitions of plagioclase, orthoclase, anorthoclase, biotite, phlogopite and garnet minerals were made using the Raman spectroscopy method and comments were made on the origin of the rock from which they were formed. Thus, the determination of the types of minerals by non-destructive analysis method has been demonstrated with examples