Chemistry and mineralogy of kimberlite-indicator mineral grains from a till survey of the Sawn Lake area (NTS 84B/13), southern Buffalo Head Hills, Alberta

The Sawn Lake map area (NTS 84B/13) covers the northwest part of the Buffalo Head Hills kimberlite field, within which 38 kimberlites have been discovered since 1997. In summer 2002, 55 till samples (with an average weight of 29 kg) were collected within the Sawn Lake map area, representing an average density of approximately one sample per 16 km2. Heavy mineral concentrates were prepared and picked for kimberlite-indicator minerals, including pyrope, eclogitic garnet, Cr-diopside, olivine, picroilmenite and chromite.

This report presents the results of 476 microprobe analyses (including three duplicate analyses) of 473 grains from the Sawn Lake map area: 427 grains from near-surface till samples; 15 grains from a subtill glaciofluvial sample collected near the K4 kimberlite complex; 10 grains from an auger-core till sample collected near the K4 kimberlite complex; 20 grains from a mantle xenolith from the K6 kimberlite; and one grain from a duplicate field sample. The microprobe data include 176 garnet, 66 chromian diopside/augite, 29 edenite/pargasite, 108 forsterite and 73 chromite analyses. The garnet data include results for 147 G9 and nine G3 (eclogitic) garnets.