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title of the thesis - Department of Geology - Queen's University

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Both <strong>of</strong> <strong>the</strong>se inferred stress directions differ from <strong>the</strong> current stress tensor in which <strong>the</strong> maximum<br />

principal stress is oriented E-W and <strong>the</strong> minimal principal stress is near-vertical (Cochrane, 1991;<br />

Coulson, 1996; Malek et al., 2008). According to Anderson (1951), this configuration <strong>of</strong><br />

maximum principal stresses should produce reverse faults. In <strong>the</strong> absence <strong>of</strong> high pore fluid<br />

pressure, it is unlikely that <strong>the</strong> steeply-dipping SW-striking shear zones in Creighton Mine could<br />

be reactivated in a reverse sense (Sibson, 1988).<br />

The medium and intermediate stresses at Creighton Mine are similar in magnitude (Coulson,<br />

1996). Inversion <strong>of</strong> <strong>the</strong> intermediate and minimum stresses would favor strike slip failure, which<br />

is possible if faults are in a state <strong>of</strong> critical stability, as proposed by McKinnon (2006). Mininginduced<br />

perturbations to <strong>the</strong> regional stress tensor are likely to produce ei<strong>the</strong>r extensional failures<br />

via reduction <strong>of</strong> normal force on shear zones (unclamping) incurred by rock extraction or stressinduced<br />

strike-slip faulting. Failure mechanisms are explored through microseismic analysis<br />

presented in <strong>the</strong> Chapter 3.<br />

39

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