Sphalerite and kimberlite indicator minerals in till from the Zama Lake region, northwest Alberta (NTS 84L and 84M)

This report presents the results and interpretations of the heavy mineral assemblages and pebble lithologies of 19 bulk till samples obtained in northwest Alberta, from the region of a sphalerite dispersal train. Indurated pebbles recovered from the 4 to 8 mm size fraction of bulk samples dominantly consist of distally derived lithologies: Canadian Shield rocks, Paleozoic carbonates and quartzite from the Athabasca Basin and the Cordillera. Three till samples contained mineralized clasts with visible pyrite and marcasite. Kimberlite indicator minerals (KIMs) including Cr-pyrope, Cr-diopside and chromite are present in trace amounts (1 to 2 grains in nine samples). Although the KIM counts are low, the samples containing KIMs do cluster in the Zama Lake - Zama City area. The source, near or far, is unknown and remains to be identified. Seven till samples contain sand-sized sphalerite grains with the largest anomaly consisting of 989 sphalerite grains recovered from a 34 kg till sample. The sphalerite is dominantly in the 0.25 to 0.5 mm size fraction (900 grains) with smaller amounts (89 grains) in the 0.5 to 1.0 mm size range. With the new data, the sphalerite dispersal train could cover an area of over 4000 km². The source of the sphalerite remains to be discovered.