Diamondiferous kimberlite in Saskatchewan, Canada — a biogeochemical study

Kimberlite was first reported in Saskatchewan in 1988. Subsequently, more kimberlite pipes have been discovered and the total diamond yield is now 160, of which some are macro-diamonds of gem quality. An investigation was made of the kimberlite outcrop at Sturgeon Lake to characterize its biogeochemical signature and assess the value of biogeochemistry in future exploration activities. At the time of the study (1989) it was the only known kimberlite in central Canada. The vegetation cover of mixed forest and farmland is dominated by trembling aspen ( Populus tremuloides), red-osier dogwood ( Cornus stolonifera), and beaked hazelnut ( Corylus cornuta). No geobotanical expression of the kimberlite could be discerned, but tissue samples from the three dominant species showed a spatial relationship to the kimberlite of enrichment in Ni, Rb, Sr, Cr, Nb, Mg and P, whereas Mn and Ba were depleted. The Ni content of dogwood twigs was substantially higher than twigs of the other species near the kimberlite. All three species were enriched in Rb and Sr relative to sites on the surrounding Cretaceous and Quaternary deposits. It is suggested that Rb may be derived from the phlogopites within the kimberlite, and mobilized during weathering as its highly soluble carbonate. Evidence suggests that biogeochemical studies to examine the distribution patterns of, in particular, Ni, Rb and Sr, may help in locating kimberlite at shallow depth, especially if there is upward movement of groundwaters to bring these elements to the root systems of the plants.