ADVANCES IN LOGGING TECHNIQUES USING IMAGING SPECTROMETERS TO CREATE MINERAL CLASSIFICATION MAPS OF DRILL CORE AND CHIP TRAYS

A case study was developed to compare the spectral results of hand held spectrometers with the spectral results of a portable imaging spectrometer solution from Terra Core International (TCI). Mineral classification maps were created from the hyperspectral imagery and compared with spectral results obtained from a Terraspec Spectrometer. The results of the comparison show that TCI’s hyperspectral core logger produced nearly identical spectral signatures when compared with spectra from the Terraspec Spectrometer. However, the most significant result was the speed at which spectra was collected for the chip trays. Because multiple chip trays could be analyzed in one scan, the time necessary to collect one 5 ft interval in a chip tray with the Terraspec Spectrometer was equivalent to 1000 ft of chip trays collected from the hyperspectral core logger; a rate 200 times faster than the Terraspec. The hyperspectral core logger also excelled at collecting image spectra from drill core. The geologist is often limited in the ability to see subtle changes in alteration and lithologic contacts, and can miss these changes even when using a hand held spectrometer. Because hyperspectral core loggers scan the entire surface of the core, subtle changes in clay alteration can now be easily identified in the imagery thus eliminating the possibility of missing important spectral information. To demonstrate this graphically, cross sections were created from the mineral classification maps and were evaluated with the geochemical results. Comparisons between the classification maps and geochemical results reveal that two main lithologies control anomalous mineralization and that quartz and illite anomalies in the core correlate directly with higher gold grades. With the addition of TCI’s hyperspectral core logging, geologists now have a cost effective and rapid technique for mineral identification in core and RC drilling.