Determination of Tourmaline Composition in Pegmatite From Buldan, Denizli (Western Anatolia, Turkey) Using XRD, XRF, and Confocal Raman Spectroscopy

Abstract

ABSTRACT Tourmaline minerals observed in different geologic environments show significant variations in terms of chemical compositions. Determination of tourmaline species gives useful petrogenetic information about both igneous and metamorphic environments. Microscopic, XRD, XRF, and confocal Raman spectroscopic features of tourmaline segregations that are 2–4 cm thick, dark-blue to black in color, and mostly fractured occurring in the Buldan pegmatite are reported. Under the microscope, tourmaline samples show indigo blue, light blue, and olive-brown pleochroism with a thin long columnar, bladed shape. They exhibit distinctive enrichments in Fe2O3 (7.83–10.16 wt%), V (245.0–591.0 ppm), Sn (70.1–147.3 ppm), W (1076.0–1887.0 ppm), U (1.2–18.2 ppm), and Th (9.6–28.0 ppm). In terms of geochemistry, the tourmaline samples are schorl with Fe/(Fe + Mg) ratios of 0.65–0.74 and Na/(Na + Ca) ratios of 0.88–0.93. Five characteristic bands of tourmaline samples are observed at 1050, 710, 370, 220–245, and 185 cm−1. Tourmaline segregations in the Buldan pegmatite are schorl in composition and are probably generated from Li-poor granitoids and their associated pegmatites.