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The Boothia Peninsula - Somerset Island region of north-central Nunavut is a frontier region (70-74°N, 94°W) long considered as part of Rae craton. Recent field mapping and acquisition of isotopic (U-Pb, Sm-Nd) data as part of the GEM-2 Boothia-Somerset project allowed this region's exposed Precambrian bedrock to be better characterized with respect to petrology and litho-geochemistry, and to be more extensively and more precisely time-calibrated. The discovery of unique, possibly exotic, basement characterized by a ca. 2.55-2.51 Ga TTG suite overlain by ca. 2.5 Ga metasedimentary rocks, cut by 2.49- 2.48 Ga plutons, are all atypical components of the Archean Rae crust. This new knowledge and the hint of similar 'Boothia terrane' crust south of Boothia Peninsula (Ryan et al., 2009), east of the Queen Maud block (Davis et al., 2014) in central Nunavut, and in northernmost Saskatchewan (Cloutier et al., 2021), raised the possibility this terrane may extend >1600 km across north-central Canada. During the foundational year of GEM-GeoNorth, the extent of Boothia terrane crust was explored through legacy samples collected during the 2012 GEM Frontiers' transect across mainland Nunavut. As part of this new study, field descriptions, photographic records and legacy samples were examined, and new U-Pb zircon geochronology was acquired. The new data and knowledge were used to: i) identify new components of Boothia terrane on the mainland southwest of Boothia Peninsula; ii) further distinguish this crust from that of Rae affinity; and iii) better constrain the depositional age of Sherman Group metasedimentary rocks. |
