Publication Type:Journal Article
Source:Geophysics, Society of Exploration Geophysicists, Tulsa, OK, United States, Volume 71, Number 3, p.M1-M9 (2006)
Keywords:Canada, chalcopyrite, copper ores, cores, eastern canada, geophysical methods, infrared methods, metal ores, Mineral exploration, mines, nickel ores, numerical analysis, Ontario, pentlandite, quantitative analysis, reflectance, Sudbury Basin, Sudbury District Ontario, sulfides, well logs
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; 3.0-30 mu m 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 1319 cm (super -1) (TIR (sub 1319) ) is linearly related to TSC%. The average of the spectral ratios TIR (sub 995) /TIR (sub 1319) and TIR (sub 1180) /TIR (sub 1319) (TIR (sub ratio) ) is related exponentially to TSC%. The coefficients of determination (R (super 2) ) based on a calibration data set are 0.90 and 0.87, respectively. Two models were tested, the TIR (sub 1319) model and the TIR (sub index) model; the latter combines TIR (sub 1319) and TIR (sub ratio) . The value for R (super 2) 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 TIR (sub 1319) model is preferred over the TIR (sub index) model because it is linear and therefore does not have the problem with insensitivity at low TSC% that the exponential TIR (sub ratio) model has. In addition, from the viewpoint of developing an instrument for automated core logging, the TIR (sub 1319) model requires measurements at only one wavelength rather than three and hence requires a less expensive instrument.
GeoRef, Copyright 2018, American Geological Institute.<br/>2006-066685<br/>thermal infrared reflectance