Till geochemistry as a technique for gold exploration in northern New Brunswick

CIM Bulletin, Vol. 81, No. 915, 1988

A.G. PRONK and D.M. BURTON,New Brunswick Department of Natural Resources and Energy, Geological Surveys Branch, Fredericton, New Brunswick

A regional till sampling program in the Upsalquitch Forks-Tetagouche Lakes area, centred some 70 km west of the city of Bathurst, has proven an effective method for gold exploration in the heavily glaciated interior of northern New Brunswick. Prospecting activities within this area over the past three years, have led to the discovery of several gold occurences associated with quartz-carbonate alteration in a variety of intrusive rock types emplaced along major fault zones. Quaternary mapping shows that the glacial history is complex. However, the displacement of material is uniform in distance and direction, and the till is generally thin (0.5 m to 2.0 m) and locally derived, making the interpretation of till geochemical patterns relatively simple for the explorationist. Previous studies have shown the the fine-grained gold is best detected in the -250 mesh (-0.063 mm) till fraction (clay plus silt) and that the C-horizon is the preferred medium for analyses. Samples were collected on a 2 km grid and analyzed for Cu, Pb, Zn, Au, Ag, As, Sb, Mn, Fe, Ni, Co, and Cd. Results indicate that concentrations of 10 to 20ppb Au can effectively delineate areas of anomalous gold in bedrock associated with fault structures, and that a good potential for discoveries exists to the west of the known occurrences, where up to 678 ppb Au has been detected in tills.

Keywords: Till geochemistry, Gold, Exploration, Bedrock geology, Mineral occurances, Quarternary geology.