The Peddie kimberlite intruded Precambrian diabase sills and Paleozoic carbonate rocks approximately 153.6 Ma ago and consists of hypabyssal facies phlogopite macrocrystic monticellite kimberlite. The subcropping surface is covered by a thin (<4 m) sequence of glacial sediments consisting of 1 to 3 m of grey silty sand till overlain in places by up to 3 m of glaciolacustrine clay. The relative abundance of indicator minerals in the Peddie kimberlite is: olivine > Mg-ilmenite >> pyrope > chromite > Cr-diopside. This relative abundance is different from other kimberlites in the Lake Timiskaming field and can be used to distinguish the Peddie dispersal train from the relatively Cr-Ti-pyrope and Cr-diopside-rich dispersal trains from the Bucke and Gravel kimberlites. The high abundance of olivine in the Peddie pipe is due to it being a hypabyssal kimberlite with fresh (i.e. non-serpentinized) olivine. Olivine in the Peddie kimberlite has survived both in-situ weathering of the kimberlite and subsequent glacial transport. Unlike tropical and arid terrains of South Africa and Australia, olivine is an excellent kimberlite indicator mineral in this glaciated terrain. Mg-ilmenite in the Peddie kimberlite is characterized by extremely high MgO (most between 9 and 18 wt.%) similar to other kimberlites nearby (Gravel, Bucke) but unlike the Kirkland Lake kimberlites 80 km to the north. Till overlying the Peddie kimberlite contains a distinctive "kimberlitic" geochemical signature defined by Ni, Ba, Nb, MgO, and P2O5 which is most apparent in the coarse to very coarse sand (0.5 to 2.0 mm) size fraction. Results of detailed kimberlite indicator mineral and till geochemical studies of the Peddie kimberlite and overlying glacial sediments have been released in GSC Open File 3775 (McClenaghan et al., 1999).

Photo of Kimberlite