Randy Stewart Hall HBSc thesis abstract
The Archean ultramafic flows found in the Henik Group, Griffin Lake Area, Northwest Territories, are texturally and chemically similar to peridotitic komatiites found in Munro Township, Ontario, and in the Barberton Mountain region, South Africa. The Henik Group flows, however, show no development of cumulate zones at the bases of the spinifex textured flows.
A small area (10.000 m2) was mapped in detail, which permitted the accurate positioning of sample locations, as well as maintaining control of the textural zone of a flow from which the sample was taken. Each flow displays a textural zonation fro a polygonal jointed quenched flow top, grading into increasingly coarser bladed spinifex in the middle of the flow, then rapidly decreasing in grain size, terminating in a fine-grained brecciated base.
A correlation exists between the texture and the geochemistry, as demonstrated in a single flow which was studied in detail. The preservation of the spinifex textures and the relatively low degree of serpentinization in this flow suggest that chemical zonation is the result of a compositional difference in the original crystalline material. The enrichment of nickel and magnesium at the top and the base of the flow is considered due to the partitioning of these elements into the earliest crystallizing phases. This partitioning results in the enrichment of silica, alumina, titanium, and iron in the residual phases in the middle portions of the flow.