HYDROTHERMAL ALTERATION SAMPLES FROM SONORA, MEX. ANALIZED WITH SWIR SPECTROSCOPY, COMPARED WITH MICROSCOPE PETROGRAPHY AND X-RAY DIFRACTION

Classic mineral identification techniques include polarized microscopy, X-ray diffraction, and energy dispersive microscopy (EDS) used in conjunction with scanning electron microscopy (SEM). At the end of the twentieth century rapid development in computer technology and the development of portable spectrometers allowed reflectance spectroscopy in the visible and short wave infrared (SWIR) wavelength range to be added as a quick, non-invasive mineral identification technique. The 21 ^st century saw development in core imagery spectrometers allowing for an in-depth understanding of the paragenesis of many different types of ore deposits.

Spectroscopy has found applications in mining and exploration fairly recently and some uncertainties need further research and clarification, for example the influence of mineral grain size and the effect of certain mineral mixtures on the resultant spectra. For this research, samples have been collected from various mines and exploration sites from Sonora, Mexico and analyzed with X-ray diffraction, petrography and hyperspectral imagery. The aim of this research is to answer questions such as what SWIR spectral response can be obtained from a 0.4 mm of plagioclase, which has been partially altered to sericite and montmorillonite; or a garnet of 0.5 mm who’s nucleus is altered to chlorite-epidote-calcite.

These investigations will help to identify and quantify mineral species and textures and also map the spatial distribution of hydrothermal alteration which would have great applications to the mining industry.