This map summarizes the field observations for the Clearwater Fiord (south) map area following eight weeks of regional and targeted bedrock mapping on western Hall Peninsula. The 2015 field campaign completes a two-decade mission to update map coverage for the whole of Baffin Island south of latitude 70°N. The bedrock is dominated by a Paleoproterozoic metaplutonic suite, ranging in composition from gabbro to syenogranite, with crosscutting relations indicating a progression from mafic to silicic magmatism. Prevailing upper amphibolite to lower granulite facies metamorphic conditions overlap the stability limits of magnetite and orthopyroxene, which is consistent with equilibrium phase diagrams and regional aeromagnetic data. Metasedimentary rocks, including quartzite, pelite, marble, and metagreywacke, are present as screens and enclaves between and within plutonic bodies. An examination of the 'ghost' stratigraphy suggests that the metasedimentary rocks can be correlated with the middle Paleoproterozoic Lake Harbour Group in the south and Piling Group in the north. Two basaltic dyke swarms and shallowly dipping Ordovician limestone respectively crosscut and overly the Paleoproterozoic units.
Integrated mapping, structural analysis, and U–Pb geochronology of the Committee Bay area, Nunavut, establish a record of Neoarchean crustal growth followed by penetrative Paleoproterozoic deformation. Supracrustal rocks include a lower ca. 2.73 Ga mafic–ultramafic volcanic-dominated sequence, a middle, economically significant 2.71 Ga intermediate volcanic-bearing sequence with intercalated sulphidized, gold-bearing iron formation, and an upper <2.69 Ga clastic ± komatiite–quartzite sequence. Following an 80 million year hiatus, this succession was intruded by voluminous ca. 2.61–2.57 Ga granodiorite–tonalite–granite ± diorite, which do not appear to have thermally or tectonically affected the supracrustal belt. Instead, three generations of structures record polyphase Paleoproterozoic deformation of the region. D 1 structures are consistent with a doubly vergent structural fan developed at ca. 2.35 Ga in response to the Arrowsmith orogeny that affected the western Rae margin. Penetrative D 2 structures dominate the map pattern and include northeast-trending, southeast-dipping folds and fabrics within which gold is localized. The general southeast dips of S 2 and inclined, northwest-vergent attitude of F 2 reflect northwest-directed shortening at 1.84–1.82 Ga. The absence of syn-D 2 plutonic rocks in the west and central Committee Bay belt support amphibolite-facies metamorphism as a response to crustal thickening, which, in turn, led to syn-D 2 crustal melting in the east. Regionally extensive upright to northwest-vergent D 2 structures and associated ca. 1.85–1.82 Ga tectonometamorphism across the Rae craton are attributed to an early stage of the Hudsonian orogeny involving microcontinent collision(s) with its southeastern margin. D 3 folds and dextral shearing at ca. 1780 Ma accommodated localized, late-stage compressional strain during final amalgamation of Laurentia.
This map synthesizes the field observations and initial interpretations for the Terra Nivea area following five weeks of regional and targeted bedrock mapping on the eastern Meta Incognita Peninsula, Baffin Island, Nunavut. Under the Geo-mapping for Energy and Minerals (GEM) Program, this area was targeted in 2014 to upgrade the geoscience knowledge and document the economic potential of the greater Iqaluit area south of Frobisher Bay. Field observations have constrained the distribution of metasedimentary units comprising quartzite, marble, psammite, pelite, and semipelite, all of which can be correlated with the contiguous middle Paleoproterozoic Lake Harbour Group in the type area north of Kimmirut. The full range of siliciclastic and minor carbonate rock types can be traced to the easternmost tip of Meta Incognita Peninsula. The distribution and eastern limit of high-grade felsic and mafic plutonic rocks, tentatively interpreted as part of the middle Paleoproterozoic Cumberland Batholith, were delineated. Three distinct phases of deformation and one metamorphic episode were recognized. The deformation and metamorphic events can be correlated with similar features and assemblages previously documented both on Baffin Island and on the Ungava Peninsula of northern Quebec, and will be utilized to compare, and improve on, existing regional tectonic models.
This map summarizes the field observations for the McKeand River (north) map area following eight weeks of regional and targeted bedrock mapping on western Hall Peninsula. The 2015 field campaign completes a two-decade mission to update map coverage for the whole of Baffin Island south of latitude 70°N. The bedrock is dominated by a Paleoproterozoic metaplutonic suite, ranging in composition from gabbro to syenogranite, with crosscutting relations indicating a progression from mafic to silicic magmatism. Prevailing upper amphibolite to lower granulite facies metamorphic conditions overlap the stability limits of magnetite and orthopyroxene, which is consistent with equilibrium phase diagrams and regional aeromagnetic data. Metasedimentary rocks, including quartzite, pelite, marble, and metagreywacke, are present as screens and enclaves between and within plutonic bodies. An examination of the 'ghost' stratigraphy suggests that the metasedimentary rocks can be correlated with the middle Paleoproterozoic Lake Harbour Group in the south and Piling Group in the north. Two basaltic dyke swarms and shallowly dipping Ordovician limestone respectively crosscut and overly the Paleoproterozoic units.
Much of the basement to the southwest Athabasca Basin comprises rocks of the Lloyd Domain. These include the Careen Lake Group, a melange of metasedimentary rocks, parts of which are correlative with Archean Murmac Bay Group and Rutledge River Basin rocks. These rocks were intruded by ca. 1985 - 1968 Ma plutons of the Taltson magmatic zone. The Lloyd Domain was divided by weakly deformed 1843 Ma granite and 2500 Ma granitic gneiss of the Clearwater Domain. To the east, supracrustal rocks of the 'Virgin schist group' are at the boundary between the Virgin River and Lloyd domains. Most basement rocks to the western Athabasca Basin were subjected to multiple deformational and metamorphic events. The Virgin River shear zone was subjected to multiple displacement episodes under ductile, brittle-ductile, and brittle conditions. Brittle reactivation of the Virgin River shear zone, along the Dufferin Lake Fault, played a role in concentrating uranium at the basal unconformity of the Athabasca Basin.
Zircons from seven granitoid samples from the southern and southwestern margins of the Athabasca Basin were dated using the SHRIMP II ion microprobe. A granite from the Virgin River shear zone was imprecisely dated at ca. 1.83 Ga. Two samples from the eastern Lloyd Domain both crystallized at ca. 1.98 Ga. These rocks were either sourced within, or intruded, 2.4 - 2.0 Ga crust. The Clearwater Domain comprises 1.843 Ga granite and 2.53 Ga granitic gneiss. Two granodioritic rocks within the basement at the western edge of the basin crystallized at 1.97 Ga. The new ages indicate that a considerable proportion of the basement to the western half of the Athabasca Basin is underlain by rocks related to the Taltson magmatic zone.
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