|Timeline:||February 2016 - 21 February 2020|
Thermal infrared (TIR) spectroscopy of rock samples and drill core is a promising method to quickly and reliably measure and analyze big datasets. To successfully apply TIR spectroscopy to determine rock composition, it is important that the measured TIR spectra accurately represent the true sample composition. However, preliminary spectroscopic results suggest that preparation methods of the sample surface influence the resulting TIR spectra.
The aim of this research is to study and quantify the effects of sample preparation and sample cleaning on the measured spectra, and quantify their effects on the projected sample composition. To determine how differences in surface roughness of the sample influence the resulting spectrum , different drill core preparation methods (e.g. saw, split and polish) and different cleaning methods (e.g. wash, air dry etc.) are applied to three different types of rocks namely, a pure quartz sandstone, a quartz sandstone that also contains kaolinite, and a fine grained gabbro. To eliminate influence of sample heterogeneity, the selected samples have a small mineral variation, homogeneous mineral distribution and a small grain size compared to the sample spot of the instrument. The TIR measurements where conducted on the Bruker Vertex 70 FTIR spectrometer, which is a non-imaging reflectance spectroscopy system with an external integrating sphere which allows for measurements in directional hemispherical reflectance (DHR). In addition to TIR measurements, other analytical methods such as SEM and morphology scanning for surface analysis, and XRF and optical microscopy for crystallographic information where conducted as well. The results of the study show the range of deterioration per influencing factor, which is translated into a standard sample preparation procedure for rocks and drill cores, ensuring consistent and correct TIR spectra.