Geology of the Qaqqanituaq Area and mafic and ultramafic geochemistry of the Hall Peninsula, Baffin Island, Nunavut
Recent regional bedrock mapping carried out on the Hall Peninsula, Baffin Island, Nunavut has revealed previously unknown rock units, structural relationships and metamorphic conditions achieved. Mafic and ultramafic rocks occur primarily intercalated with metasedimentary rocks in the east-central region of the Hall Peninsula. Focused mapping was carried out in the Quaqqanituaq Area (QA), now the type locality for metasedimentary-mafic/ultramafic occurrences on the Hall Peninsula. The QA records an east-west compression event, D1, which produced in the dominant regional S1 fabric and tight, nearly isoclinal F1 folds. The QA also records a north-south compression event, D3 (regional D2 event not observed in QA) resulting in an S3 crenulation cleavage and open F3 folds. U-Pb detrital zircon geochronology and U-Pb geochronology of a cross-cutting monzogranite dyke bracket sediment accumulation and mafic/ultramafic intrusion/extrusion between 2.13 and 1.87 Ga and place a maximum age on D1 at 1.87 Ga. Garnet – biotite – K-feldspar – ± sillimanite mineral assemblages observed in QA pelites indicate that upper amphibolite facies metamorphic conditions were reached. This observation is empirically confirmed by the implementation of winTWQ software which indicates that the peak pressure and temperature conditions reached in the QA were 4.8±2.1 kbars and 645±50°C. Whole-rock major and trace element geochemical data was obtained for 75 mafic and ultramafic samples from all regions of the Hall Peninsula including 20 from the QA. Mafic samples were classified on the basis of N-MORB normalized trace element geochemistry as being alkaline (La/Sm ~ 4.9; Gd/Yb ~ 2.7), calc-alkaline (La/Sm ~ 4.3; Gd/Yb ~ 2.4), tholeiitic (La/Sm ~ 2.1; Gd/Yb ~ 1.1), or transitional (La/Sm ~ 2.7; Gd/Yb ~ 1.6). A negative Nb anomaly, which is on average 5.4 times lower with respect to Th and Ce is observed in all mafic samples with the exception of alkaline mafic rocks. On the basis of their geochemical profiles and comparative study of adjacent terrains, the mafic rocks are concluded result from partial melting a subduction modified mantle source during plume-initiated rifting of the North Atlantic Craton.
DegreeMaster of Science (M.Sc.)
CommitteeEglington, Bruce; Pan, Yuanming; Buatois, Luis; Bethune, Kathy
Copyright DateDecember 2014
Geochemistry, Structural Geology, Geothermobarometry, Geochronology