Metallogenic Considerations for Devonian Carbonates in the Fort McMurray and Fort Vermilion Areas, Alberta: A Contribution to the Carbonate-Hosted Pb-Zn (MVT) Targeted Geoscience Initiative

During the 2001 field season, the Alberta Geological Survey mapped and sampled selected sections of Upper Devonian carbonate rocks in northern Alberta near Fort McMurray, Vermilion Chutes and on Harper Creek. Twelve whole rock and 53 trace element analyses by conventional geochemistry indicate the samples collected have low economic potential. Field observations confirmed that the investigated areas are part of the Alberta Basin basinal fluids discharge system inferred to have economic potential for metallic minerals accumulation. Updip, bedding-parallel fluid migration through the carbonate sequence resulted in very limited dolomitization, locally intense iron alteration and isolated development of centimetre-size sulphide nodules. Intense recrystalization and iron-staining is associated with vertical structural discontinuities and with the Devonian-Cretaceous unconformity. Vertical tensional fractures and joints appear to be the main channelways for warm/hot mineralizing fluids. The only two carbonate-hosted lead and zinc anomalies previously reported in the investigated area are related to areas characterized by zones of vertical fracturing. The carbonate exposures examined so far along major rivers represent only a minor part of the Devonian carbonate sequence of northern Alberta. Possible metallogenic processes associated with structurally controlled fluid conduits observed in the investigated areas warrant further investigations for metallic minerals within the Western Canada Sedimentary Basin stratigraphy.