Heather Archibald

Regional gravity surveys and geologic mapping in the southwestern Central Gneiss Belt, Ontario, Grenville Province show gravity anomalies associated with the Parry Sound and Kiosk domains. Twenty-five year old two-and-a-half-dimensional (2.5 D) models of the Parry Sound domain gravity anomaly have been revised, incorporating constraints from new geological mapping and seismic reflection profiles. In the revised models the general shape and extent of the Parry Sound domain is essentially unchanged from the original models. The Kiosk domain is a poorly known terrain of granulite facies high strain gneiss separated by a shear zone from underlying amphibolite facies gneiss. 2.5 D models of the Kiosk domain constrained by over 250 density measurements and field mapping indicate that the Kiosk domain is rhomboid shaped and with boundaries dipping to the southeast at about 30 degrees to a depth of about 20 to 25 km where they flatten out. Contrary to suggestions of a proposed Lower Go Home-Lower Rosseau-Kiosk thrust sheet, the Kiosk domain and adjacent McCraney subdomain have been interpreted as large blocks that are separate from the proposed Lower Rosseau-Lower Go Home thrust sheet. From the modeling results it is suggested that the Allochthon Boundary Thrust (ABT) extends to the north of the Bonfield batholith and not along the northern boundary of the Kiosk domain.

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Pages: 72
Supervisor: Nicholas Culshaw