Deformation history and tectonic significance of the Sanagak Lake shear zone, Boothia Peninsula, Nunavut

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Drayson, Derek, Camacho, Alfredo, Sanborn-Barrie, Mary, Regis, Daniele, Larson, Kyle, Osinchuk, Alix, DuFrane, S. Andrew
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2022
• Subjects: General Earth and Planetary Sciences; Nunavut; Hudson; Boothia Peninsula; Sanagak Lake; Committee Bay
• Online Access: http://dx.doi.org/10.1139/cjes-2022-0046; https://cdnsciencepub.com/doi/full-xml/10.1139/cjes-2022-0046; https://cdnsciencepub.com/doi/pdf/10.1139/cjes-2022-0046

The recently recognized Sanagak Lake shear zone (SLsz) is a 165 km long, southwest striking corridor of high-strain rocks that transects the southern portion of Boothia Peninsula, Nunavut. This zone records pervasive deformation (D SL1 ) at conditions of ∼0.52 GPa and ∼700 °C, and localized deformation (D SL2 ) at ≥0.5 GPa and 300–500 °C that preserve left lateral and right lateral senses of movement, respectively. Neocrystallized D SL1 titanite in a hornblende-bearing granodiorite yields an age of 1804 ± 6 Ma, interpreted to be the timing of D SL1 . The timing of D SL2 is loosely bracketed by 40 Ar/ 39 Ar hornblende (1814 ± 3 Ma) and biotite (1743 ± 1 Ma) cooling ages since the deformation temperature falls between the estimated closure temperature of these minerals. Similar rock types and metamorphic conditions on either side of the shear zone rule out the SLsz as a terrane boundary. Rather, strain localization may have been triggered by thermal softening related to the emplacement of a northeast-trending belt of high-temperature granites south of the shear zone between 1840 and 1820 Ma. Deformation and metamorphism at ca. 1.81 Ga south of Boothia Peninsula and in the central Rae (Committee Bay belt) have been attributed to the Superior Province colliding with the southeastern margin of the Rae craton, such that the SLsz may too have formed in response to far-field stresses derived from this collision. The absence of ca. 1.81 Ga tectonic fabrics north of the shear zone indicates that the SLsz marks the northwestern extent of mid-crustal, Trans-Hudson related tectonometamorphism.