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TitleLocalisation of the brittle Bathurst fault on pre-existing fabrics: a case for structural inheritance in the northeastern Slave craton, western Nunavut, Canada
AuthorMa, S M; Kellett, D AORCID logo; Godin, L; Jercinovic, M J
SourceCanadian Journal of Earth Sciences vol. 57, no. 6, 2019 p. 725-746,
Alt SeriesNatural Resources Canada, Contribution Series 20190145
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
NTS76G/09; 76G/16
Lat/Long WENS-106.5000 -106.0000 65.9167 65.5000
Subjectsstructural geology; geochronology; economic geology; Science and Technology; Nature and Environment; bedrock geology; basement geology; structural features; faults; fault zones; fabric analyses; structural trends; tectonic history; deformation; thermal history; intrusions; dykes; hydrothermal alteration; radiometric dating; uranium lead dating; argon argon dating; zircon dates; fluid dynamics; permeability; mineral deposits; unconformity-type deposit; uranium; Bathurst Fault; Slave Craton; Kilohigok Basin; Thelon Tectonic Zone; Thelon Basin; Paleoproterozoic; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; stereonet projections; photographs; photomicrographs; block diagrams; tables; Concordia diagrams; geochronological charts; plots; bar graphs
ProgramTargeted Geoscience Initiative (TGI-5) Uranium ore systems
Released2019 10 16
AbstractThe north-northwest-striking Bathurst fault in the northeastern Slave craton displaced the 1.9 Ga Kilohigok basin and the ca. 2.02-1.96 Ga Thelon tectonic zone, and projects beneath the 1.7 Ga Thelon basin where unconformity-associated uranium deposits are spatially associated with basement faults. Here we investigate the deformation-temperature-time history of the Bathurst fault rocks using structural and microstructural observations paired with U-(Th-)Pb and 40Ar/39Ar geochronology. Highly strained hornblende-bearing granitoid rocks, the predominant rock type on the northeastern side of the Bathurst fault in the study area, show ambiguous sense of shear suggesting flattening by coaxial deformation. Quartz and feldspar microstructures suggest ductile deformation occurred at >= 500 °C. Along the main fault trace, brittle features and hydrothermal alteration overprint the pervasive ductile flattening fabric. In situ U-Th-Pb dating of synkinematic monazite suggests ductile fabric formation at ca. 1933 ± 4 Ma and ca. 1895 ± 11 Ma, and zircon from a cross-cutting dyke constrains the brittle deformation to <= 1839 ± 14 Ma. 40Ar/39Ar dating of fabric-defining minerals yield cooling ages of ca. 1920-1900 Ma and ca. 1900-1850 Ma for hornblende and muscovite, respectively, and a maximum cooling age of ca. 1840 Ma for biotite. We suggest the ca. 1933-1895 Ma ductile flattening fabric developed during orthogonal collision and indentation of the Slave craton into the Thelon tectonic zone and Rae craton. Brittle deformation on the Bathurst fault was localised parallel to the ductile flattening fabric after ca. 1840 Ma and preceded Thelon basin deposition. Brittle deformation features in Bathurst fault rocks preserve evidence for fluid-rock interaction and enhanced basement permeability, suggesting the fault is a possible conduit structure for mineralising fluids.
Summary(Plain Language Summary, not published)
The Bathurst fault is a major break in the Earth's crust at the northeastern edge of the Archaen Slave craton, Nunavut. We have used structural geology and geochronology methods to reconstruct its formation during the Paleoproterozoic geological era. Our observations and analytical results show that the brittle fault formed within and parallel to a pre-existing tectonic fabric, and we have more tightly constrained the timing of both the early fabric and formation of the fault. Hydrothermal alteration associated with brittle faulting shows that this structure has been a major conduit for fluids through Slave crust during its history.

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