<p> The igneous rocks of the Killarney Complex, Killarney, Ontario
exhibit numerous echelon fracture sets near their contact with mylonites of
the Grenville Front. The echelon fracture sets are younger than the Grenville
Front mylonites and are therefore part of the late brittle history of the
Grenville Province. These fracture sets are confined to a small (5 km2) area
but display a wide range of orientations and morphologies. They can be divided
into four peak orientations and these can be compared with inferred stress
states for several periods in the tectonic history of the Grenville Province
from 1200 Ma to the present. Based on these orientations and other
observations it is suggested that the echelon fracture sets formed over a
period of time spanning the end of the Grenvillian Orogeny 1000 Ma)
to the beginning of Ottawa-Nippissing rifting (post 575 Ma). </p> <p> Measurement of the geometrical characteristics of the echelon
fracture sets and comparison with those quoted in the literature has led to the
conclusion that the geometry of an echelon fracture set does not unequivocally
indicate its origin or mode of formation. </p> <p> Current models using fracture-zone angle and overlap ratio for the
classification of echelon fracture sets seem to be unapplicable to the echelon
fracture sets examined in this study and must be used with caution. The
echelon fracture sets studied here are interpreted to have formed in "shear
zones" and to consist of dominantly tensile fractures. Some of the fractures
have originated as shear fractures or have undergone shearing at some point in
their history. </p> / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19558 |
| Date | 08 1900 |
| Creators | MacKinnon, Paula |
| Contributors | Clifford, P.M., Geology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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