The Mineral Deposits Potential of the Marguerite River and Fort McKay Areas, Northeast Alberta (NTS 74E)

This report provides a preliminary assessment of the potential for metallic mineral deposits in the Precambrian, Devonian and Cretaceous rocks in the Marguerite River and Fort McKay areas of northeastern Alberta. The field portion of this study focused on the geological examination and geochemical sampling of selected bedrock exposures. However, in order to supplement the poor bedrock exposure and to test for a possible relationship between gold and discharging brines in the Bitumount map area, selected core from coal exploration drillholes was also examined and sampled. As well, nine till and three fluvial sediment samples were collected for geochemical analysis and diamond indicator mineral analysis in order to assess the viability of sampling surficial materials to aid exploration. Lastly, a study of the till stratigraphy in the Bitumount area was undertaken. This till study incorporates unpublished field data obtained by the Alberta Geological Survey during the middle 1980's along the Firebag River.

Several new sulphide and radioactive occurrences were discovered in the Marguerite River area. Elevated concentrations of up to 191 parts per million (ppm) copper, 343 ppm zinc, 44 ppm cobalt, 210 ppm nickel, 500 ppm chromium and 163 ppm vanadium were obtained from samples that were collected from pyrite and pyrrhotite occurrences in a 2 to 4 km wide mylonite zone in Precambrian rocks. Radioactive occurrences in peraluminous megacrystic syenites to granitoids yield up to 3,000 counts per second with a SRAT SPP2N scintillometer, and assays of up to 350 ppm uranium, 1,900 ppm thorium, 3,300 ppm cerium,1,900 ppm lanthanum and 1,200 ppm neodymium, along with elevated contents of other rare earth elements and base metals such as lead, zinc, bismuth and molybdenum.

Samples collected from recent carbonate material associated with a springwater discharge site in the Fort McKay area yielded 0.5 ppm silver, 54 ppm lead, 16 ppm arsenic, 120 ppm chromium, 1.2 ppm antimony, 9 ppm vanadium, 39 ppm boron, 18 ppm bromine, and 472 ppm strontium. A sample of Devonian Waterways Formation carbonate yielded 118 ppm lead and 32 ppm antimony. Anomalous concentrations of gold up to 837 parts per billion (ppb) were detected in oil stained or impregnated Cretaceous coal, shale and sandstone in core from five coal exploration drillholes in the Firebag River area. A positive correlation exists between elevated concentrations of gold and elevated values for chromium (up to 553 ppm) and, to a lesser extent, silver (up to 1.1 ppm) and vanadium (up to 39 ppm). Other anomalous elements associated with elevated concentrations of gold include up to 61 ppm copper, 97 ppm lead, 211 ppm zinc, 58 ppm nickel, 35 ppm cobalt, 14 ppm arsenic,951 ppm strontium, 4 ppm antimony, 6 ppm bismuth and 257 ppm boron.

Geochemical results for the till samples include up to 9 ppb gold, 0.7 ppm silver, 14 ppm arsenic, 97 ppm zinc, 32 ppm copper, 12 ppm bromine and 570 ppm fluorine. Based on the microprobe results of potential diamond indicator minerals, there are no grains indicative of either kimberlite, lamproite or peridotitic source rocks, with the possible exception of four chrome diopsides. However, five G3 and twenty-two G5 eclogitic garnets were identified by microprobe analysis, several of which have favourable chemistry plotting within the diamond inclusion field for eclogitic garnets on scatter plots of total iron versus magnesium and titanium versus calcium. In addition , several of the eclogitic garnets contain sufficiently high amounts of sodium and titanium such that they border on the diamond inclusion field for eclogitic garnets on a plot of titanium versus sodium.

The results from the 1993 fieldwork at the Marguerite River to Fort McKay area, plus the ongoing work by the Geological Survey of Canada and recent exploration results announced by industry, indicate that the potential for the discovery of metallic mineral deposits in the Bitumount map area north of Fort McMurray is much higher than previously believed. Potential deposit types to explore for include: brine and/or hydrocarbon-related gold deposits; Archean shear zone hosted gold deposits; Mississippi Valley type lead-zinc deposits; sediment hosted base metal deposits with one or more of zinc, lead, copper, nickel, silver and gold; granitoid-related uranium and/or rare earth element, precious metal or base metal deposits; unconformity-related, sandstone-hosted or vein-type uranium deposits, diamondiferous kimberlite or lamproite diatremes; and various types of placer or paleoplacer deposits, with the important metals/minerals being gold, diamonds, titanium or other 'heavy minerals'.