Satellite Geological Mapping of the Yellowknife Volcanic Belt

An ARIES III Image Analysis System was used to manipulate digitized Landsat 5 Thematic Mapper (TM) imagery of the Yellowknife Volcanic belt (YVB) to demonstrate geological applications of this technology in a boreal region characterized by subdued topography, open-canopy forest cover and about 50% outcrop exposure. The YVB was selected for study because detailed geological mapping is available against which com- puter-generated imagery could be compared and evaluated. The study area encompasses a northerly trending belt of principally mafic volcanic rocks (Kam Group) flanked to the west by a multi-phase batholith (Western Granodiorite Complex) and to the east by turbiditic sediments (Burwash Formation) and granitic stocks. Intermediate volcanic rocks (Banting Group) and a narrow belt of conglomerates (Jackson Lake Formation) separate the Kam Group from the Burwash Formation. Initially, images from each of the six TM channels were analyzed, and it was found that channels 7 (short-wave infrared), 3 (red) and 2 (green) yield the best discrimination of geological features. Subsequently, various computer-generated enhancement programs were applied to these channels to intensify geological discrimination, and the resulting images were combined to produce a number of false-colour composite images that were com- pared to published geological maps. On the best of these "satellite geological maps" at least three phases of igneous intrusions can be identified, as well as the boundaries of the Kam Group and a number of important structural discontinuities. The adjacent Banting Group volcanics and Burwash Formation sediments could not be chromatically separated but are sometimes distinguishable using textural criteria. Most notably, certain computer-enhanced images highlight two zones of alteration within the Kam Group that have not previously been noted on published maps. These alteration zones appear to be spatially asso- ciated with a number of gold showings and one significant gold deposit. It is concluded that computer manipulation of satellite imagery can add worthwhile information to the geological database of areas that have been mapped at a detailed scale of 1:lO OOO.