A regional stream sediment and heavy mineral concentrate survey, Churchill Falls, Labrador

CIM Bulletin, Vol. 74, No. 829, 1981

JOHN E. CALLAHAN, Geology Department,, Appalachian State University, Boone, North Carolina

A stream sediment geochemical survey covering an area of 13,000 sq. km near Churchill Falls, Labrador, was conducted for Brinex (British Newfoundland Explorations Ltd.) prior to partial flooding by the Churchill Falls power project. Stream sediments (minus 80-mesh) were analyzed for Cu, Pb, Zn, Ni, Ag, Mo, UandMn, and the heavy mineral, nonmagnetic fraction (minus 60-mesh)for Cu, Pb, Zn, Ni, Ag, Mo, Ba andMn. A binocular examination of the concentrates for sulphides and pyrope garnet was done on the heavy mineral concentrates. The concentrates were also examined for fluorescent minerals. Two distinct areas with high trace-element values indicate the need for follow-up studies. The first is in an area ofgabbro erratics containing massive and disseminated sulphides (pyr-rhotite, pyrite and minor chalcopyrite) on the western edge of the survey area along the Esker Road. The second, largest area (several hundred square kilometres) is anomalous in U and Mo and associated with felsic intrusives (Red Wine Complex?), syenites, granite gneiss and sedimentary rocks (Seal Lake Group?).The binocular study showed that almost 15% of the heavy mineral concentrates contained pyrite and no other sulphides. This indicates that this technique may be worthwhile in determining the presence of sulphide minerals in stream sediments from glaciated environments. The only fluorescent mineral observed in the study was zircon.

Keywords: Exploration, Geochemical exploration, Stream-sediment surveys, Heavy-mineral concentrates, Churchill Falls area, Labrador, Copper, Lead, Zinc, Silver, Nickel, Manganese, Molybdenum, Uranium, Barium.