Quantification of elemental composition of Granite Gneiss collected from Neelum Valley using calibration free laser-induced breakdown and energy-dispersive X-ray spectroscopy

Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) has been employed for elemental analysis of Granite Gneiss, rock sample, collected from Neelum Valley of Azad Jammu & Kashmir, Pakistan. The sample was irradiated with focused laser beam from Q-switched Neodymium Yttrium Aluminum Garnet laser, having 532 nm wavelength and pulse width of 5 ns, and the emission spectrum was recorded with a spectrometer. Overall, ten elements viz. Si, Al, K, Fe, Sr, Ca, Mg, Na, Li, and H were identified by inspecting the characteristic emission lines. Out of ten detected elements, seven elements fulfilling the criteria of calibration-free technique, namely: Si, Al, K, Fe, Sr, Ca, and Mg, were quantified. Sample was also analyzed by employing energy-dispersive X-ray spectroscopy (EDX) and the results confirmed the presence of all those elements in the sample that were detected by LIBS, except Li and H. For the most abundant element Si in the Granite Gneiss sample, a significant agreement of two techniques for the quantitative results is obtained. Both the techniques have confirmed that Granite Gneiss consists mainly of Si with abundance of 72.75% and 71.30% by weight as measured by CF-LIBS and EDX, respectively. Findings of study show that for the elements with minor concentrations, quantitative results as measured with both techniques were not in close agreement.