Zircon Morphology and UPb Geochronology in Active Shear Zones: Studies On Syntectonic Intrusions Along the Northwest Boundary of the Central Metasedimentary Belt, Grenville Province, Ontario

At least some of the domains within the Central Gneiss Belt may have been metamorphosed prior to 1150 Ma.

“At least some of the domains within the Central Gneiss Belt may have been metamorphosed prior to 1150 Ma (van Breemen et al. 1986;Yuccillo et al. 1992).”

Mineral ages obtained for the Britt domain provide evidence for a major tectonothermal episode at about 1450 Ma and a later metamorphic overprint at ca. 1050 Ma.

“Mineral ages obtained for the Britt domain provide evidence for a major tectonothermal episode at about 1450 Ma and a later metamorphic overprint at ca. 1050 Ma (Easton 1986;van Breemen et al. 1986;Tuccillo et al. 1992).”

Thrusting of the Central Metasedimentary Belt over the Central Gneiss Belt occurred at ca. 1160 Ma and 1060 Ma.

“Thrusting of the Central Metasedimentary Belt over the Central Gneiss Belt occurred at ca. 1160 Ma and 1060 Ma as indicated by U-Pb ages from syn-deformational pegamtites within the Central Metasedimentary Belt Boundary Zone (van Breemen and Hanmer 1986;McEachern et al. 1990).”

The lack of evidence for a thermal event at about 1150 Ma for the Britt domain is in striking contrast to the history of most other domains, which show evidence for this metamorphism in addition to the younger overprint at about 1070 to 1050 Ma.

“The lack of evidence for a thermal event at about 1150 Ma for the Britt domain is in striking contrast to the history of most other domains, which show evidence for this metamorphism in addition to the younger overprint at about 1070 to 1050 Ma (Easton 1986;van Breemen et al. 1986).”

An earlier thrusting event along this fault has been dated at ca. 1160 Ma, which coincides with the oldest sphene age (sample 89-13) from the NE Bancroft domain.

“An earlier thrusting event along this fault has been dated at ca. 1160 Ma (van Breemen and Hanmer 1986;McEachern et al. 1990), which coincides with the oldest sphene age (sample 89-13) from the NE Bancroft domain.”

Thrusting of the Parry Sound over the Britt domain at ca. 1160 to 1120 Ma is recorded in zircons from syn-deformational pegmatites and garnets from within the shear zone.

“Thrusting of the Parry Sound over the Britt domain at ca. 1160 to 1120 Ma is recorded in zircons from syn-deformational pegmatites (van Breemen et al. 1986) and garnets from within the shear zone (Tuccillo et al. 1992).”