QUATERNARY GEOLOGY AND TILL GEOCHEMICAL INVESTIGATIONS IN NORTHERN NEW BRUNSWICK, CANADA

The glacial history of northern New Brunswick is complex and a general absence of datable surficial materials and stratigraphic sections makes precise timing of events problematic. Thin, locally derived homogeneous basal till over most of the area, erratic pebbles and boulders at the highest elevations, preglacially weathered bedrock overlain by till, and a similar glacial history to adjacent areas, suggests that the entire area was glaciated during the Late Wisconsinan. The preservation of preglacially weathered bedrock indicates that Quaternary glacial erosion in some areas was relatively weak. Orientations of striations, grooves, roche moutonnées, glacially sheared bedrock, till fabrics, fluted bedrock, eskers, and DeGeer moraines indicate a multidirectional ice-flow history responsible for till deposition. A minority of clasts are transported from bedrock sources up–ice but >75 percent of the pebbles are generally derived from the underlying bedrock unit. Some clasts and boulders can be found up to 20 km down-ice (east-northeast) from their source. Laurentide erratics that traveled considerably larger distances are present in northwestern New Brunswick.

Results of 2 km spaced till geochemical data (approximately 10,000 samples) revealed several base metal (Cu, Pb, Zn etc.) and Au anomalies with anomalous pathfinder elements, as well as isolated spot-highs. Detailed deposit-scale studies at several massive sulfide deposits and copper skarn occurrences indicate that basal till geochemical anomalies are reflections of well defined dispersal trains <500 m long. The Zn-Pb-Cu-Ag deposits of the Bathurst Mining Camp (BMC) are best detected by till geochemical methods using In, Sn, Pb, Cu, As, and Ag in the <0.063 mm fraction. There are high Zn concentrations in till at many deposits but in till overlying gossan at some deposits Zn is depleted making it less useful for detecting sulfide mineralization. Till samples spaced 250 m apart can be used to detect base-metal mineralization in the BMC.