Exploration vectors from near-infrared spectrometry near the McLeod volcanogenic massive sulphide deposit, Matagami District, Quebec.

Discussion is presented of the spectral characteristics of alteration minerals in two effusive rhyolites, forming the immediate footwall and hanging wall of the Archean McLeod VMS deposit in the Matagami mining district, Quebec, Canada. Three NIR parameters were measured from drill cores from the Bracemac-McLeod mining area: the ratio of white mica over white mica pluys chlorite; white mica composition as expressed by the AlOH spectral absorption peak wavelength, and chlorite composition mapped with the FeOH spectral absorption peak wavelength. Twenty-two individual drill cores taken from 0 to 1 700 m from the ore were examined to assess systematic proximal to distal variations. It was found that the clearest gradient was obtained for white mica composition in the footwall rhyolite; the AlOH spectral absorption peak wavelength systematically decreases laterally as the ore zone is approached. The AlOH spectral spectral absorption feature is weaker in the hanging wall because these rocks are generally less altered. The chlorite composition (FeOH wavelength) or mineral proportions were less successful at defining gradients at the McLeod deposit.
Discussion is presented of the spectral characteristics of alteration minerals in two effusive rhyolites, forming the immediate footwall and hanging wall of the Archean McLeod VMS deposit in the Matagami mining district, Quebec, Canada. Three NIR parameters were measured from drill cores from the Bracemac-McLeod mining area: the ratio of white mica over white mica pluys chlorite; white mica composition as expressed by the AlOH spectral absorption peak wavelength, and chlorite composition mapped with the FeOH spectral absorption peak wavelength. Twenty-two individual drill cores taken from 0 to 1 700 m from the ore were examined to assess systematic proximal to distal variations. It was found that the clearest gradient was obtained for white mica composition in the footwall rhyolite; the AlOH spectral absorption peak wavelength systematically decreases laterally as the ore zone is approached. The AlOH spectral spectral absorption feature is weaker in the hanging wall because these rocks are generally less altered. The chlorite composition (FeOH wavelength) or mineral proportions were less successful at defining gradients at the McLeod deposit.