Coeval development of dome-and-keel and linear accretionary architectures in the eastern Wabigoon superterrane, Canada: geology and geochronology

The eastern Wabigoon superterrane in the Superior Province, Canada, comprises two belts with contrasting tectonic architectures. The Onaman–Tashota belt has a dome-and-keel architecture and consists of granitoid intrusions surrounded by infolded Mesoarchean to Neoarchean (2975–2719 Ma) metavolcanic rocks and younger Neoarchean (2710–2695 Ma) metasedimentary rocks. It is characterized by D 1 fabrics, folds, and deformation zones, which formed parallel to intrusion-volcanic contacts at 2700 to 2683 Ma. The Beardmore–Geraldton belt, located south of the Onaman–Tashota belt, has a linear accretionary architecture and consists of interleaved 2725 Ma metavolcanic rocks and 2700–2694 Ma metasedimentary rocks. Interleaving occurred between 2694 and 2690 Ma during the same D 1 event. Orogen-parallel D 2 folds, cleavage, and sinistral deformation zones overprint the D 1 structures in both belts. They formed between 2683 and 2665 Ma at transitional greenschist to amphibolite facies temperatures > 515 °C in the Onaman–Tashota belt, and greenschist facies temperatures in the Beardmore–Geraldton belt. D 3 dextral transpression occurred late and reactivated early D 1 –D 2 deformation zones in both belts. Although the two belts underwent the same sequence of deformation events, the coeval development of dome-and-keel and linear accretionary structures suggests that different factors controlled the development of D 1 structures. Higher density contrasts, hotter weaker crust, and possibly lower strain rates in the Onaman–Tashota belt resulted in the formation of uniformly distributed dome-and-keel structures, while lower density contrasts, strong planar anisotropies, and possibly higher strain rates favored the development of linear accretionary structures in the Beardmore–Geraldton belt.