EPR characteristics of quartz from tungsten deposits at Degana and Balda, Rajasthan, India

Abstract

In continuation of our study on the defects in solids, quartz samples were collected from three types of tungsten ores in Degana, India, namely granite-hosted lode, stockwork ore in phyllite and breccia ore in granite, and from tungsten-mineralized quartz vein at Balda, India. The samples were prepared for electron paramagnetic resonance (EPR) analysis at various irradiation intervals and for annealing to understand the effect of gamma irradiation and annealing on the intensity of the free radicals and structural impurities. The analysis was carried for (a) raw samples before gamma irradiation and annealing, (b) samples irradiated for 30 and 60 min, (c) samples annealed at 500°C for 12 h, (d) samples annealed at 500°C and irradiated for 1 h, (e) samples annealed at 900°C for 1 h and (f) samples annealed at 900°C and irradiated for 1 h. The concentration of sodium in vein quartz of Degana and Balda tungsten deposits is in the range of 0.04–0.06 wt%. After annealing the quartz sample at 900°C for 1 h, the [GeO4/Na+] center is observed in EPR spectra, suggesting the incorporation of sodium in a quartz lattice.