Geology of the Aviat Kimberlites, Melville Peninsula, Nunavut Canada
Kimberlites of the Aviat cluster were first discovered on the Melville Peninsula, Nunavut, in 2002. The Aviat kimberlite cluster intruded into the Archean - Paleoproterozoic basement rocks of the northern Rae Craton at approximately 535Ma. The 10 kilometre by 3 kilometre kimberlite cluster comprises sheets and pipe-like bodies with variable styles of emplacement. Three kimberlite pipes have been identified along a four kilometre strike length, within and south of a NW-trending sinistral strike-slip regional fault zone. North of the fault zone, an eastern sheet complex comprises sets of stacked, subhorizontal to shallow-dipping hypabyssal kimberlite sheets which have been broadly delineated over a 10 km2 area. The eastern sheet complex forms a conical to radial pattern dipping inward toward the NW-trending fault system.
The kimberlite sheets display variable thickness along dip, and thicken (to 7m) downdip toward the NW-trending fault system. Locally the sheets are planar features, however in a regional context variable attitudes indicate corrugations in the overall sheet geometry. The sheets are dominated by olivine macrocrystic phlogopite-carbonate hypabyssal kimberlite, with localized development of hypabyssal kimberlite breccia along the hanging wall contacts of thicker (>4m) sections. The three small pipe-like bodies (AV1, AV4, AV9) are infilled with similar lithologies, with textures ranging from hypabyssal kimberlite to tuffisitic kimberlite breccias and a spectrum of transitional textures between these end members. The AV267 portion of the eastern sheet complex returned a sample grade of 162 cpht from a 20.6 tonne sample collected in 2007, the AV1 pipe returned a grade of 88 cpht from 59.19 tonnes. Diamond endowment and characteristics do not display significant variation between the different textural end members within the pipe-like bodies, nor between the pipes and sheet occurrences.
The majority of the Aviat kimberlite bodies have been discovered while prospecting in the vicinity of anomalous till sample locations. Due to magnetically complicated bedrock responses the pipe-like bodies at Aviat are not obvious anomalies and exposed windows into the sheet complex are not apparent in the geophysical data. The eastern sheet complex bodies have no obvious correlation with local bedrock foliation, joint, or fault orientations.