Semi-quantitative laser-induced breakdown spectroscopy for analysis of mineral drill core

An investigation is reported in the use of time-resolved laser-induced breakdown spectroscopy (LIBS) for mineral assaying applications. LIBS has potential for the rapid on-line determination of the major and minor constituents of mineral drill core samples. In this work a Q-switched Nd:YAG laser is used to test as-received lengths of drill core, with remote LIBS signal acquisition via a bare optical fiber bundle coupled to a spectrometer. A novel normalization scheme, based on integrating the total plasma emission, is demonstrated as a method for correction of signal variations due to the uneven surface geometry of rock. Averaged intensities of atomic emission for the elements Cr, Cu, Fe, Mn, and Ni show good linear correlations, with coefficients of R2 = 0.92-0.99, against laboratory assay values. Limitations in the comparison of the results of surface analysis to bulk compositions are discussed, with emphasis on mining applications of LIBS