A total of 1253 kimberlite indicator minerals, 174 in the 0.5-2 mm fraction and 1079 in the 0.25 to 0.5 mm fraction, were reported by Garrett and Thorleifson (1993). The most abundant class consisted of 776 Cr-diopsides. A total of 206 Cr-pyropes (G7, G9, G10) including 12 G10 subcalcic Cr-pyropes, 136 titanian Cr-pyropes (G1, G2, G11), and 25 eclogitic garnets (titanian, calcic, magnesian almandines; G3, G4, G6) were initially identified. In excess of 76% of each of these mineral groups occurred in the finer 0.25 to 0.5 mm fraction. After the follow-up re-analysis, 76 garnets were re-classified as eclogitic using a lowered minimum TiO2 value (>0.2%; Thorleifson et al., 1994). Magnesian ilmenite showed the greatest tendency to occur among the coarse grains, of a total of 110 Mg-ilmenites only 52% were obtained from the 0.25 to 0.5 mm fraction.

The indicator minerals are concentrated in southwestern Saskatchewan, west-central Manitoba, and central Saskatchewan. Five of the G10 garnets, the best known predictor of diamond, were obtained in southern Manitoba. Additional occurrences of G10 garnets are scattered across southern Saskatchewan to the Alberta border. Indicator minerals in southwestern Saskatchewan show a spatial relationship to the outcrop of the Miocene Wood Mountain Formation. Therefore, the possibility of at least one stage of preglacial fluvial transport has to be considered in determining the ultimate provenance of these minerals.

After re-analysis of the 156 eclogitic and near-eclogitic garnet grains, 4 were found to contain marginally anomalous Na concentrations, >0.06% Na2O. Three are from western Manitoba and adjacent Saskatchewan, and the remaining grain is from southwestern Saskatchewan.

The Ni determinations by proton microprobe on the kimberlitic garnets were used in a geothermometry study. Using the assumption of a 40 mW/m2 geotherm (Griffin et al., 1989) and assuming acceptable calibration to other instruments, 13% of the garnets, mostly G11s, report temperatures above the diamond stability field (>1250 C°, >75 ppm Ni), 31% are in the diamond stability field (32-75 ppm Ni), and 56% are cooler (<950 C°, <32 ppm Ni). Of the grains in the Griffin diamond window (950-1250 C°, 32-75 ppm Ni), 80% contain <50 ppm Zr, a positive sign regarding diamond grade (Griffin and Ryan, 1993). These grains occur in Alberta, Saskatchewan, and Manitoba, with clusters around Diefenbaker Lake and Prince Albert.

Indicator minerals obtained from the till samples were transported by the continental ice sheet during the Pleistocene. Hence they were carried to the sampling sites by at least the final ice flow in the region. The dominant ice flow was towards the west and southwest, as indicated by drift composition in the region (e.g. Shetsen, 1984). This was overprinted in many areas by southeastward flow in late glacial time (Prest et al., 1968; Dyke and Prest, 1987). In most cases, the grains are likely to have undergone a complex transport history involving repeated glacial transport, and possibly interglacial and/or preglacial fluvial transport.

Useful evidence for interpreting glacial transport history was provided by lithological classification of the 8-16 mm fraction and the bulk mineralogy of the 63 to 250 µm non-ferromagnetic heavy mineral fraction. These patterns include abundant brown carbonate pebbles in southern Manitoba and southeastern Saskatchewan, a high concentration of shale clasts in southwestern Manitoba, the highest concentration of Precambrian Shield pebbles in Saskatchewan north of the Saskatchewan River, and Cordilleran-derived pebbles in the western half of southern Alberta. Heavy mineral counts indicate abundant garnet and hornblende in central Saskatchewan, as well as relatively more epidote and titanite near Winnipeg.

Geochemical data from till reveal broad-scale patterns that can be related to provenance. In addition, a number of elements exhibit single element patterns that, even though they are of low geochemical contrast, may be related to mineral occurrences.

The most notable feature in the data is a high carbonate, low As, zone in the vicinity of southern Manitoba Paleozoic carbonate occurrences. However, of greater interest is the rapid dilution of the high carbonate till with Cretaceous shale material immediately to the west and southwest on the Manitoba Escarpment, and the persistence of an elevated carbonate pattern as far west as the Missouri Coteau, a northwest-trending escarpment lying west of Estevan-Regina-Saskatoon. In addition, the western carbonate domain of Shetsen (1984) is clearly visible in the data in the form of elevated carbonate values in the Calgary region. The majority of the data for the remaining elements show an inverse response, i.e., the carbonate terrain of eastern and central Manitoba are reflected by trace-element lows.

Tills down ice flow from Cretaceous shales of the Manitoba Escarpment are characterized by higher levels of Fe, Mn, V, Mo, As, Sb and Zn, and to a lesser extent Cu and Ni, than the tills to the east or west. The Cd pattern is slightly different, whilst following the same general pattern, the highest values are concentrated in the northern tills in the Duck Mountain and Tisdale areas.

The line of the Missouri Coteau west of Estevan-Regina-Saskatoon appears to mark the boundary between tills of different regional geochemical compositions. The transition is most clearly seen in the data for Total Carbonate, Fe, V, As, Rb, Ba and Br, and to a lesser extent with Pb, Zn and Cr. The Br data are of interest as the area east of this lineament is characterized by a zone of elevated levels.

Till north of the Saskatchewan River is characteristically low in a number of trace-elements in comparison with areas immediately to the south and/or west, e.g., V, Mo, U, Br, As and Zn. In contrast, Na and Th show the opposite, and are locally enriched; it is postulated that this may be due to the tills of the area containing a large proportion of Cretaceous Manville sediments or Precambrian Shield derived material. It is noteworthy that this area is also characterized by the highest amphibole contents in the heavy mineral separates.

A number of elements increase in level to the northwest in Alberta relative to the area to the south, e.g., Fe, V, Cu, Ni, Cr, Th, Sc, Rb and As. This is likely a lithological control being exerted on the till composition. Shales are more widespread to the north and northwest, in comparison to the likely trace element poorer Tertiary sandstones and Foothills carbonates in the west.

The major task ahead is the interpretation of the chemical, mineralogical and lithological data for the tills. These data provide evidence for multiple ice advances from the northeast and east, and later advances from the north. There is also a suggestion that many of the surface tills east of the Missouri Coteau, except along the Manitoba Escarpment and in parts of the Interlakes region, have been transported long distances prior to deposition. In contrast, west of the Missouri Coteau, and particularly in the southern part of the survey area the surface tills may be of more local provenance.

The geochemical patterns in the C horizon soil data closely follow those observed for the tills. However, as soils were collected at all sites some patterns relate to the fluvial derivatives of the tills, e.g., coarser grained quartz-rich fluvial and eolian sands, etc., and clay-sized material of glaciolacustrine sediments. These two groups are characterized by generally lower trace-element levels in the coarser, quartz-rich, sediments and higher values for many elements in fine-grained parent materials. The A horizon samples have been influenced by pedological processes that have led to a modification of the C horizon patterns through concentration and depletion for different elements in different areas and soil regimes. These data are of particular interest to agricultural and environmental scientists, e.g., Cd (Garrett, 1994) and Hg (Garrett and Thorleifson, 1994).