Aeromagnetic signature of an exhumed double dome system in the SW Grenville Province (Canada)

Abstract

Analysis of aeromagnetic data in the Grenville Province reveals the presence of two regional‐scale unmapped structural domes (the Morin and Mékinac‐Taureau domes) with an oval‐shaped magnetic pattern bounded by regional‐scale shear zones and a geometry that is similar to that produced in crustal flow models under extension, which predict two upright domes of foliation (double dome) separated by a steep shear zone. The Mékinac‐Taureau dome, a metamorphic core complex, and the Morin dome may have been exhumed by channel flow. Exhumation occurred by a combination of thrust, normal‐sense and wrench shear zones. The preservation of paragneisses in the Morin dome suggests that it underwent a lesser degree of exhumation than did the Mékinac‐Taureau dome. This study shows how the integration of local field information with magnetic data in a regional tectonic setting can reveal and delineate concealed gneiss domes and highlights a role for strike‐slip tectonics in the creation of regional structures involving the exhumation of deep crust.

Numerical analysis of the role of radiogenic basement on temperature distribution in the St. Lawrence Lowlands, Québec

“…The domal structure of the Mékinac Taureau domain(Fig. 4), interpreted as being exhumed during crustal extension by Soucy La Roche et al(2015), has subsequently been attributed from geophysical data to the presence of an underlying, contemporaneous AMCG body byDufréchou (2017), which our unpublished geophysical data support. Sinistrally oblique extension along the Tawachiche shear zone (TSZ) on the E margin of the Morin Terrane, marking the mapped contact with the Portneuf-Mauricie domain, occurred between 1065 and 1035 Ma (Soucy La Roche et al 2015).…”

Late Ottawan orogenic collapse of the Adirondacks in the Grenville province of New York State (USA): Integrated petrologic, geochronologic, and structural analysis of the Diana Complex in the southern Carthage-Colton mylonite zone

“…However, a potential drawback of model 2 is that if the Highlands were at least partially migmatitic at the time of exhumation (Bickford et al, 2008), it is expected that a dome structure, potentially with sub-domes (e.g., Whitney et al, 2013), should be evident in the Highlands, as is seen in the Morin and Mékinac-Taureau domes to the north (Dufréchou, 2017). To date, no domes or sub-domes that could be connected to exhumation have been described in the Highlands.…”

“…0.98 Ga (Rivers, 2008;McLelland et al, 2010). However, recent work within the Grenville province also emphasizes the importance of tectonic collapse late in its history, as exemplified by work in the Adirondacks, the Morin terrane, the east side of the Mékinac-Taureau domain, and the Ottawa River Gneiss Complex Wong et al, 2011;Rivers and Schwerdtner, 2015;Soucy La Roche et al, 2015;Schwerdtner et al, 2016;Dufréchou, 2017;Regan et al, 2019).…”

Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

“…The importance of extensional deformation in the Grenville province has been increasingly recognized, especially as a mechanism for producing metamorphic discontinuities (Rivers, 2008(Rivers, , 2011. However, many of the interpreted extensional structures and tectonic implications have been made within Québec and Ontario, Canada (Busch et al, 1997;Rivers, 2011;Soucy La Roche et al, 2015;Dufréchou, 2017), and there remains a lack of detailed structural syntheses incorporating regional extensional models for Mesoproterozoic rocks elsewhere in the Grenville province. The recognition of extensional structures and processes elsewhere in the Grenville province will help illuminate a more regionally scaled extensional framework and its role in ore mineralization, leucogranite emplacement, exhumation of lower-to middle-crustal rocks, and the overall architecture of a classic hot, large, and long-duration orogeny (Rivers, 2008).…”

“…Rocks of the Grenville province record multiple phases of tectonism (polycyclic belt of Rivers [2008]), and are the result of multiple accretionary phases preceding the culminating collision with Amazonia during the Ottawan phase of the Grenville orogeny. Collision and resulting northwestward thrusting occurred prior to 1082 Ma in parts of Québec (Soucy La Roche et al, 2015), and were immediately followed by the onset of crustal extension that was predominately southeast vergent (Rivers and Schwerdtner, 2015), represented by, for example, the Ottawa River Gneiss Complex (Rivers and Schwerdtner, 2015;Schwerdtner et al, 2016), the Robertson Lake shear zone (Busch et al, 1997) Buddington (1939) La Roche et al, 2015), and the Tawachiche shear zone (Soucy La Roche et al, 2015;Dufréchou, 2017). Furthermore, classic extensional dome structures have been inferred from geophysical data, for example, the Morin dome (Dufréchou, 2017).…”