TY - JOUR

T1 - High-pressure, high-temperature rocks from the base of thick continental crust

T2 - Geology and age constraints from the Manicouagan Imbricate Zone, eastern Grenville Province

AU - Indares, Aphrodite

AU - Dunning, Greg

AU - Cox, Richard

AU - Gale, David

AU - Connelly, Jim

PY - 1998

Y1 - 1998

N2 - The Grenville Province of the Canadian Shield is composed of crustal material with laurentian affinities, involved in continental collision during the Grenvillian Orogeny between 1.19 and 0.98 Ga. In the eastern Grenville Province, the Manicouagan Imbricate Zone (MIZ) is composed of Paleoproterozoic (Labradorian, ~1.6 Ga) and Mesoproterozoic (Pinwarian, ~1.4 Ga) crustal segments that were metamorphosed under high-pressure, high-temperature (high-P-T) conditions (P~1800 MPa and 800°<<900°C) and intruded by synmetamorphic gabbroic stocks and dykes and postmetamorphic granite, during a ~1.0 Ga crustal shortenting event in the Grenvillian Orogeny. The gabbroic dykes display high-P mineral assemblages and a within plate tholeiite signature attesting to the intrusion of asthenospheric melts during the high-P metamorphsim. The structural configuration of MIZ is that of a thrust stack (Lelukuau terrane) overlain by an extensional assembly of slice (Tshenukutish terrane). To the north, Llelukuau terrane overlies Archearn basement and Paleoproterozoic supracrustal rocks of the Gagnon terrane along a thrust contact. Tshenukutish terrane is tectonically overlain to the south by crustal slices composed of pre-Grenvillian and early Grenvillian lithologic units that are correlative with those in MIZ, but which were at midcrustal levels during the Grenvillian Orogeny (low-P segment of the eastern Grenville Provicne), and were intruded by anorthosite and granitoids farther south.A likely tectonothermal evolution of MIZ at ~1.0 Ga involves crustal shortening by imbrication in a postsubduction phase of continental collision, followed by (convective?) removal of the underlying thickened lithospheric mantle and the rise of hot asthenospheric material close to the base of the crust. Exhumation of MIZ likely occurred from the basal levels of the crust and was achieved by (1) NW directed thrusting over a crustal-scale ramp (Archean basement of the Gagnon terrane) with coeval extension at the higher levels of the pile (stage 1 extension) and (2) a second extension event (stage 2 extension) coeval with emplacement of postmetamorphic granite at the boundary between MIZ and the low-P segment.

AB - The Grenville Province of the Canadian Shield is composed of crustal material with laurentian affinities, involved in continental collision during the Grenvillian Orogeny between 1.19 and 0.98 Ga. In the eastern Grenville Province, the Manicouagan Imbricate Zone (MIZ) is composed of Paleoproterozoic (Labradorian, ~1.6 Ga) and Mesoproterozoic (Pinwarian, ~1.4 Ga) crustal segments that were metamorphosed under high-pressure, high-temperature (high-P-T) conditions (P~1800 MPa and 800°<<900°C) and intruded by synmetamorphic gabbroic stocks and dykes and postmetamorphic granite, during a ~1.0 Ga crustal shortenting event in the Grenvillian Orogeny. The gabbroic dykes display high-P mineral assemblages and a within plate tholeiite signature attesting to the intrusion of asthenospheric melts during the high-P metamorphsim. The structural configuration of MIZ is that of a thrust stack (Lelukuau terrane) overlain by an extensional assembly of slice (Tshenukutish terrane). To the north, Llelukuau terrane overlies Archearn basement and Paleoproterozoic supracrustal rocks of the Gagnon terrane along a thrust contact. Tshenukutish terrane is tectonically overlain to the south by crustal slices composed of pre-Grenvillian and early Grenvillian lithologic units that are correlative with those in MIZ, but which were at midcrustal levels during the Grenvillian Orogeny (low-P segment of the eastern Grenville Provicne), and were intruded by anorthosite and granitoids farther south.A likely tectonothermal evolution of MIZ at ~1.0 Ga involves crustal shortening by imbrication in a postsubduction phase of continental collision, followed by (convective?) removal of the underlying thickened lithospheric mantle and the rise of hot asthenospheric material close to the base of the crust. Exhumation of MIZ likely occurred from the basal levels of the crust and was achieved by (1) NW directed thrusting over a crustal-scale ramp (Archean basement of the Gagnon terrane) with coeval extension at the higher levels of the pile (stage 1 extension) and (2) a second extension event (stage 2 extension) coeval with emplacement of postmetamorphic granite at the boundary between MIZ and the low-P segment.

U2 - 10.1029/98TC00373

DO - 10.1029/98TC00373

M3 - Journal article

AN - SCOPUS:0031710810

VL - 17

SP - 426

EP - 440

JO - Tectonics

JF - Tectonics

SN - 0278-7407

IS - 3

ER -