Overview of bedrock mapping and results from portable X-ray fluorescence spectrometry in the eastern part of the Tehery Lake– Wager Bay area, western Hudson Bay, Nunavut

The Tehery-Wager geoscience mapping activity is a four-year initiative conducted by the Geological Survey of Canada and the Canada-Nunavut Geoscience Office. The project aims to gather new geoscience knowledge to create modern bedrock and surficial geological maps, evaluate the economic potential in the area and characterize the tectonic, magmatic, depositional and metamorphic history of the rock units therein. The first of two field seasons of bedrock geological mapping in the Tehery Lake–Wager Bay area, north of Chesterfield Inlet, Nunavut in 2015 focused on better documentation and characterization of rock types and features across the eastern part of the study area. Major lithological units include Archean tonalite to granodiorite gneiss, monzogranite to syenogranite gneiss, K-feldspar–phyric monzogranite (likely correlative with the 2.6 Ga Snow Island suite), presumed Proterozoic supracrustal rocks, undeformed monzogranite to syenogranite (likely correlative with the 1.85–1.81 Ga Hudson suite) and roughly coeval ultrapotassic clinopyroxenite to syenite intrusions. Portable X-Ray fluorescence (pXRF) spectrometry analyses of mafic to intermediate orthogneiss, and amphibolite layers in the tonalite to granodiorite orthogneiss and metasedimentary panels, were collected in the field. The interpreted data suggest that the rocks have diverse, variably metasomatized basaltic to andesitic compositions. Least altered samples range from primitive and mantle-like to more evolved compositions that, coupled with diverging multi-element patterns, point to multiple, chemically distinct subpopulations within the basaltic sample suite. The preliminary results highlight the advantage of in situ, real-time and nondestructive pXRF measurements as a chemostratigraphic tool that can be used in the field to support bedrock mapping.