Oliver Baker, BSc

The last glaciation of the Laurentide Ice Sheet (LIS) modified the Canadian landscape and discontinuously deposited glacial sediment of various types over bedrock, including mineral deposits. Glacial sediment produced and dispersed by basal ice and subglacial processes (i.e., till), contain a compositional blend that reflects the bedrock source regions, including sources of potential interest for critical minerals. This study focuses on a core region of the LIS in northern Quebec and Labrador that experienced ice divide migrations, which led to multiple distinct ice flow phases that transported till in different directions. Previous analyses in the region showed evidence of longer dispersal trains in the clast lithology and indicator minerals, while major oxides from the till matrix geochemistry mostly reflect the underlying bedrock, indicating shorter transport distances. This study aims to use trace elements from till matrix geochemical data to determine their impact on dispersal train models by comparing their dispersal signal to those of indicator minerals and major oxides to better understand past ice flow dynamics and sediment source regions. The methods involve a data exploration phase, followed by a log-ratio transformation and standardization to address the constrained nature and log-normal distributions of compositional data. Principal Component Analysis (PCA) is then applied to reduce the dimensionality of the multivariate dataset and to reveal key compositional signatures. K-means clustering of PCA results then groups the elements into compositional assemblages. Results are then analyzed and interpreted in their spatial context to establish relationships with bedrock and glacial landscape features, and to map sediment dispersal patterns. Preliminary findings show similar patterns to that of the major oxides, with the trace elements having slightly greater dispersal magnitudes. These findings, along with previous work, suggest that the fine fraction of the till contains a dominant local provenance signature, whereas distal bedrock sources are more easily identified in the coarser fractions (pebbles, indicator minerals). Ongoing research is now focusing on the potential causes of this discrepancy in dominant bedrock sources and related transport distances and on the implications to mineral exploration in the region. The findings from this study will contribute valuable insights into the glacial dynamics of the region, thus enhancing future ice flow reconstructions and mineral exploration strategies.