Diabase dyke swarms in the Lac de Gras area, Northwest Territories, and their significance to kimberlite exploration: initial results

Abstract

In the Lac de Gras area, geochemical composition and field relationships characterize five Proterozoic diabase dyke swarms and provide data for the development of a tectonic model of dyke emplacement that has implications for kimberlite exploration. Patterns in dyke characteristics (age, orientation, geochemical composition, paleomagnetism) divide the dykes into populations, whose spatial relationship to known kimberlite pipes is tested using GIS and Bayesian techniques. Three Paleoproterozoic dyke swarms (Malley, MacKay, Lac de Gras), both individually and combined as a single population, have a moderate to strong spatial association with known kimberlite bodies. No apparent spatial asso- ciation exists between younger dyke swarms (Mackenzie and 305° ) and known kimberlite bodies.The oldest dyke sets are subparallel to known faults and/or joint sets. The evaluation of the role of early structures in controlling the orientation of Paleoproterozoic dykes requires a better understanding of the age of these faults.