Analysis of the structural and tectonic environments associated with rock-mass failures in the mines of the Sudbury District

A chronological analysis of the intrusive and structural features that cross-cut the Sudbury Igneous Complex and the associated orebodies, demonstrates that a system of late-stage faults and fractures form the youngest structural features in the area.;The faults and fractures form an orthogonal pattern and field evidence indicates that they are contemporaneous. The pattern of fractures observed to have formed in intact rock by a Richter magnitude 2.2 rockburst is similar to the pattern of late-stage faults and fractures. The fault pattern is compatible with experimental results determined from loading samples in a three-dimensional strain field.;Analyses of violent failures and non-violent failures demonstrate that many failures occur in the immediate vicinity of the late-stage faults and fractures.;The in situ stress field in the Sudbury District is a tectonic stress field which has formed the late-stage faults and fractures. (Abstract shortened by UMI.);The late-stage fractures are steeply dipping and strike WNW to NNE. They are commonly infilled with calcite and/or secondary sulphides. They occur in an echelon patterns forming distinct fracture zones that vary in width from several m to several tens of m.