Orphan and Elusive Glacial Dispersal Trains from Kimberlites in the Lac de Gras AreaTuesday, November 20, 2018 - 15:00 to 15:19 Theatre 1
Numerous glacial dispersal trains, spatially and compositionally associated to kimberlites, have been characterized and mapped in the Lac de Gras region, Northwest Territories (NT). However, a small number of these trains have yet to be associated with a source. Additionally, a number of known sub-cropping kimberlites do not have well-defined, spatially associated, trains of indicator minerals. These issues suggest that local factors may be important in controlling the occurrence, shape, and strength of a dispersal pattern and its spatial association with a kimberlite. Identifying these factors and understanding their effect on the dispersion of indicator minerals could provide a road map for finding additional diamondiferous kimberlites in the NT and elsewhere.
Here we examine contrasting dispersal trains from south and southwest of Lac de Gras, as well as situations where the source of known dispersal trains (e.g., Coppermine Train) continue to elude exploration geologists. Using both surface and subsurface datasets, we find that the bedrock geology and topography of the source area, as well as those of the dispersal area, are potential key controls on the type and shape of dispersal patterns. Even across discontinuous drift and subdued shield relief we find that bedrock topography and lithology modulated the effect of glacial dynamics on till production and provenance. These 'bedrock factors' have interacted in various ways during Quaternary glaciations, in combinations unique to each case, to generate complex dispersal patterns in three dimensions. Accounting for these factors, using both surface and subsurface data, could enhance the success of drift exploration programs and improve their outcome in the glaciated shield terrains of northern Canada.