QUATERNARY GEOLOGY AND TILL GEOCHEMISTRY OF NORTHWESTERN NEW BRUNSWICK - NATMAP

Quaternary mapping, till sampling (1380 sites), and drift prospecting in northwestern New Brunswick complements stream sediment, geophysical, and bedrock mapping surveys. The project area is underlain by Lower Paleozoic sedimentary rocks of the Grog Brook, Matapedia, and Fortin groups within the Chaleur Uplands and Edmundston Highlands physiographic subdivisions.

The area is covered by thin (< 1m thick) basal till or a veneer of broken bedrock/weathered bedrock/colluvium. Glaciofluvial deposits occupy several of the major water courses. In the western part of the area, glacial striations indicate that ice movement was along major valleys in a general east-southeast to southeast direction. Several outcrops in the extreme western part of the area indicate ice flow in a westerly direction. Boulder erratics, some transported from as far away as the Canadian Shield, were found near the striated outcrops. Analysis of the pebble size fraction of the till indicates that the pebbles, and therefore the till, are locally derived.

Geochemical analysis (ICP-MS) was performed on the 63µm size fraction. Geochemical results at 50 sites in the vicinity of the Patapedia skarn occurrences indicate anomalous concentrations of several elements in till directly over the surface expression of the mineralization (466 ppm Cu, 589 ppm Pb, 813 ppm Zn, 3.4 ppm Ag, and 65 ppb Au). Isolated anomalous concentrations were also detected in the regional till data above the background values of 20 ppm Cu, 20 ppm Pb, 75 ppm Zn, 0.05 ppm Ag, and 2 ppb Au.

A large area of anomalous Ni and Co in till is coincident with magnetic and stream sediment anomalies. Boland and Ritchie brooks, containing the highest concentration of Ni in stream sediments, drain the till-covered plateau where the highest Ni concentrations in till are found. This area is underlain by fine-grained sedimentary rocks of the Boland Brook Formation. Anomalous Ni concentrations in till east of the magnetic anomaly and east of a large area of regolith containing colluvium and broken bedrock, may reflect eastward glacial dispersal. Till overlying sedimentary rocks of the Fortin Group in the western part of the study area, generally contains the lowest concentrations of metals.