Surface and Subsurface Till Characteristics in a Drumlin Field South of Lac de Gras, NT; Implications for Drift ProspectingTuesday, November 20, 2018 - 16:00 to 16:19 Theatre 1
Successful diamond exploration is becoming increasingly challenging as the best expressed targets have been found. Areas of variable drift thickness and heterogeneous surficial deposits present several challenges to exploration. One particular aspect that is poorly understood is the effect of well-developed drumlin fields on the surface expression of dispersal trains. Our study focuses on drumlin fields and their potential effects in the expression of a dispersal pattern. Because drumlins are often stratified we hypothesize that multiple till layers of contrasting provenance, representing multiple ice-flow directions, can occur at the surface across drumlin fields due to erosional processes. This has the potential to affect analysis and interpretation of surficial till dispersion data.
To test this hypothesis, we examined data from a large RC drilling dataset donated by Dominion Diamond Ekati Corp. and North Arrow Minerals Inc. and complemented it with field-based surficial geology observations and analysis of additional surficial till samples across targeted drumlins. The surficial samples were collected at the top and on the sides of drumlins to test whether any glacial stratigraphy is expressed, especially in areas where post-glacial erosion may have exposed internal drumlin stratigraphy. Based on the RC data and available maps drift thickness within the drumlin field ranges from 1 meter in the swales between drumlins to about 20 meters on the top of the highest amplitude drumlins. Locally measured ice-flow indicators (n=11) show three distinct ice-flow directions from older to youngest: 260, 290, 305 degrees. Preliminary analysis of textural and compositional data shows variations within the till at depth as well as across the drumlin field. Ongoing work focuses on determining the relationship (or lack thereof) between till characteristics, drumlins, and ice flow history (till provenance), as well as on three-dimensional dispersal patterns of kimberlite indicator minerals and related geochemical pathfinders. This work will highlight landform feature considerations by using multiple parameters to analyze sample data in areas with complex glacial geology and high diamond potential.