Mapping altered rocks using Landsat TM and lithogeochemical data: Sulphurets-Brucejack Lake District, British Columbia, Canada / Картографирование измененных горных пород с использованием спутника Landsat TM и литогеохимических данных: Сернистые отложения

Landsat Thematic Mapper [TM) data have been used to detect the presence of altered rocks associated with ore mineral deposition. In arid environments, the spectral signatures of diagnostic minerals are often not masked by water, vegetation, or suxficial materials. There are many studies in which TM data have been used to locate hydrothermally altered rocks in near desert regions, but few successful examples can be found that relate to glaciated, vegetated terrain at high latitudes. In this paper, TM data, in concert with lithogeochemical data and field observations, are used to detect and map altered rocks in the Sulphurets-Brucejack Lake district of northwestern British Columbia.
Areas of iron-pyrite and phyllic [sericitic) alteration as well as areas of intense silicification have been located using band ratioing techniques. The chemical nature of these alteration zones has been established through comparison with lithogeochemical data. These alteration styles reflect the underlying rock type, as would be expected, but also appear to reflect two different styles of alteration, perhaps reflecting different mineralizing systems. The western half of the study area, characterized by iron-pyritic alteration, reflects a base metal [Cu porphyry and minor Au) system while the eastern half, characterized by areas of silicification and clay alteration, may represent a precious metal (Au, As, Sb) system. <...>