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Sixteen kimberlite boulders were collected from three sites on the Munro and Misema River Eskers in the Kirkland Lake kimberlite field and one site on the Sharp Lake esker in the Lake Timiskaming kimberlite field. The boulders were processed for heavy-mineral concentrates from which grains of Mg-ilmenite, chromite, garnet, clinopyroxene and olivine were picked, counted and analyzed by electron microprobe. Based on relative abundances and composition of these mineral phases, the boulders could be assigned to six mineralogically different groups, five for the Kirkland Lake area and one for the Lake Timiskaming area. Their indicator mineral composition and abundances are compared to existing data for known kimberlites in both the Kirkland Lake and Lake Timiskaming areas. Six boulders from the Munro Esker form a compositionally homogeneous group (I) in which the Mg-ilmenite population is very similar to that of the A1 kimberlite, located 7–12 km N (up-ice), directly adjacent to the Munro esker in the Kirkland Lake kimberlite field. U–Pb perovskite ages of three of the group I boulders overlap with that of the A1 kimberlite. Three other boulders recovered from the same localities in the Munro Esker also show some broad similarities in Mg-ilmenite composition and age to the A1 kimberlite. However, they are sufficiently different in mineral abundances and composition from each other and from the A1 kimberlite to assign them to different groups (II–IV). Their sources could be different phases of the same kimberlite or—more likely—three different, hitherto unknown kimberlites up-ice of the sample localities along the Munro Esker in the Kirkland Lake kimberlite field. A single boulder from the Misema River esker, Kirkland Lake, has mineral compositions that do not match any of the known kimberlites from the Kirkland Lake field. This suggests another unknown kimberlite exists in the area up-ice of the Larder Lake pit along the Misema River esker. Six boulders from the Sharp Lake esker, within the Lake Timiskaming field, form a homogeneous group with distinct mineral compositions unmatched by any of the known kimberlites in the Lake Timiskaming field. U–Pb perovskite age determinations on two of these boulders support this notion. These boulders are likely derived from an unknown kimberlite source up-ice from the Seed kimberlite, 4 km NW of the Sharp Lake pit, since indicator minerals with identical compositions to those of the Sharp Lake boulders have been found in till samples collected down-ice from Seed. Based on abundance and composition of indicator minerals, most importantly Mg-ilmenite, and supported by U–Pb age dating of perovskite, we conclude that the sources of 10 of the 16 boulders must be several hitherto unknown kimberlite bodies in the Kirkland Lake and Lake Timiskaming kimberlite fields.

Glacial history studies and analysis of heavy mineral separates from glacial sediments (till and eskers) were undertaken in theBoothia mainland area of central Nunavut. Mapping of surficial macroforms and glacial striae has shown a complex, four phase ice-flow history. From oldest to youngest, the ice-flow history entails: Phase 1 to the north, Phase 2 to the northeast, Phase3 to the east, and Phase 4 to the north. Late-stage, localized ice-flows were determined in some areas, especially around the Harrison Uplands. All of the regional ice-flow phases impacted on the final distribution of glacial erratics in till, but with varied influence, wherein Phase 2 to the NE and Phase 4 to the N in the southern part of Boothia mainland were the most significant glacial dispersal events. During Phase 2, glacial transport distances of greater than 100 km were determined for Paleozoic carbonates and Paleoproterozoic members of the Chantrey Group siliciclastic (pelites, orthoquartzites), and at least 20 km for the Paleoproterozoic marble member of the Chantrey Group. Kimberlite indicator minerals (including mantle ilmenite, forsterite, Cr-diopside, eclogitic and peridotitic (G9) garnets, chromite, perovskite and lyndsleyite) and visual gold grains were found in glacial sediments. Prospective zones for kimberlites or gold mineralization are outlined herein from heavy mineral analysis and knowledge of the ice-flow history.

This report presents results of till sampling in the vicinity of the Peddie kimberlite, Bucke Township, in the Lake Timiskaming kimberlite cluster of northeastern Ontario. Thirty till samples were collected (mainly south) of the Peddie kimberlite to document the nature of glacial dispersal from the kimberlite, using both indicator minerals and till geochemistry. Most of the kimberlite indicator minerals in till were found in the finest of the three size fractions (0.25 to 0.5, 0.5 to 1.0 and 1.0 to 2.0 mm) of heavy mineral concentrates examined. Till in the vicinity of the Peddie kimberlite contains a distinctive kimberlitic geochemical signature defined by Ni, Cr, Nb, and Ta, which is most apparent in the coarse to very coarse sand (0.5 to 2.0 mm) and the silt+clay (