Quantifying total sulfide content of cores and cut-rock surfaces using thermal infrared reflectance Available to Purchase

In this study, core samples of sulfide-rich zones were delineated from their host rock and a quantitative estimation of sulfide content on cut-rock faces was made using thermal infrared reflectance (TIR; $3.0–30μm$ region) spectroscopy. Core sections and rocks were collected from mines in the Sudbury basin, Ontario, Canada. The TSC% (areal percentage of total sulfide content) of each sample was then estimated by summing the modal abundance of all sulfide minerals (chalcopyrite, pyrrhotite, and pentlandite). TIR at $1319cm−1$$(TIR1319)$ is linearly related to TSC%. The average of the spectral ratios $TIR995/TIR1319$ and $TIR1180/TIR1319$$(TIRratio)$ is related exponentially to TSC%. The coefficients of determination $(R2)$ based on a calibration data set are 0.90 and 0.87, respectively. Two models were tested, the $TIR1319$ model and the $TIRindex$ model; the latter combines $TIR1319$ and $TIRratio$⁠. The value for $R2$ for predicted TSC% versus observed TSC% (from thin sections) is 0.98 and 0.97, respectively, with little or no bias. The standard deviation of the residuals is 3.1 and 3.5 TSC%, respectively. The $TIR1319$ model is preferred over the $TIRindex$ model because it is linear and therefore does not have the problem with insensitivity at low TSC% that the exponential $TIRratio$ model has. In addition, from the viewpoint of developing an instrument for automated core logging, the $TIR1319$ model requires measurements at only one wavelength rather than three and hence requires a less expensive instrument.