Till Geochemistry in West-Central Manitoba: Interpretation of Provenance and Mineralization Based on Glacial History and Multivariate Data Analysis

Abstract

Till geochemical datasets from archived samples in west-central Manitoba are interpreted using multivariate data analytical techniques such as principal component analysis and pathfinder element index methods, combined with a spatial representation of the data in a geographic information system (GIS). Results show that carbonate till derived from Hudson Bay, as expressed by the (Ca + Mg)/Na ratio, is found predominantly east of Leaf Rapids and extends south into the Northeastern Kisseynew Domain. A 30- to 70-km-wide zone is documented beyond the limit of dissolvable carbonate dispersal that contains till of Labradorean provenance with low Ca-Mg-Mn-Te concentrations, noncalcareous till of Keewatin provenance, and silty calcareous till at depth. The variation in till provenance, together with the predominance of southwesterly ice-flow indicators, suggests that carbonate dispersal occurred prior to deglaciation, and that surface tills in the zone of confluence between Labradorean and Keewatin ice are likely the result of recycling of calcareous tills and/or carbonate-leached sandy tills, mainly by Keewatin ice. The newly defined limits of carbonate and Ca-rich till, typically used to assess provenance and glacial transport, provide a new framework for evaluating the significance of till geochemical patterns when drift prospecting over the Trans-Hudson orogen. Several regional- to local-scale dispersal trains from geochemically distinct bedrock sources are discussed in terms of elemental association, glacial transport characteristics, and potential bedrock sources. The multivariate statistical approach combined with GIS mapping also highlights new areas with small multi- or single-element enrichments that may be of further interest for volcanogenic massive sulfide exploration or for potentially more detailed drift sampling.