The Geological Survey of Canada (GSC) has studied kimberlites in the Kirkland Lake area, northeastern Ontario to document glacial dispersal patterns and geochemical signatures associated with kimberlite. This work has been conducted because of the lack of published information on glacial dispersal of kimberlite. The Kirkland Lake area is ideal for this study because the locations of the kimberlite pipes and dykes are well known and they are easily accessible. Bedrock in the region is covered by glacial sediments, from a few metres to 100 m thick. By applying a combination of drift prospecting and geophysical methods, several kimberlite pipes and dykes have been discovered within the last 14 years. Kirkland Lake kimberlites intruded Archean rocks and overlying Paleozoic carbonate rocks during the Late Jurassic, between 155-159 Ma. Since then, the overlying Paleozoic rocks have been completely eroded and the kimberlite pipes have been eroded down to the mid to lower portions of the diatremes. Kimberlite, being relatively soft, was differentially eroded by preglacial weathering and glaciers such that kimberlite pipes subcrop 20 to 50 m below the surrounding bedrock. Many deeply eroded kimberlite pipes in the Lac de Gras kimberlite field, NWT, are detectable because they are now very deep lake basins. The Kirkland Lake pipes, in contrast, have been completely filled in with thick sequences of glacial drift and have no surface expression.

Four kimberlite pipes and one dyke were examined to document kimberlite composition, glacial dispersal patterns, down-hole geophysical signatures and surficial geochemical signatures. These pipes were chosen in order to examine glacial dispersal patterns in till (C14, B30, A4, Buffonta) and in esker sediments (Diamond Lake). Glacial sediment and kimberlite samples were collected from 31 overburden holes drilled around the four kimberlite pipes by the GSC in the winter of 1993. Archived samples of kimberlite and glacial sediments from reverse circulation holes drilled by the Ontario Geological Survey (KLIP project) and by Sudbury Contact Mines Ltd. also were used in the study. Kimberlite indicator minerals (pyrope, Cr-diopside, Mg-ilmenite, chromite, olivine) were picked from the 0.25 to 2.0 mm non-ferromagnetic fraction of glacial sediments and kimberlite and analyzed at the GSC electron microprobe lab. Till also was analyzed geochemically to evaluate its potential use as an kimberlite exploration tool. Soil and vegetation overlying the C14 and Diamond Lake pipes and the Buffonta kimberlite dyke were collected to examine surficial signatures associated with kimberlite. Highlights of the research are presented here along with the major conclusions drawn from the work.