Natural Resources Research Institute Technical Report

Project No. 563102At least 17 faults are located within the Peter Mitchell Mine. Most of the faults trend north to north-northeast; four faults trend northwest. The faults are near-vertical, with offsets ranging from 50 feet. Thirteen of the faults display a "scissors-type" offset in that the relative displacement along the length of the fault is more pronounced toward one end of the fault. In 10 faults, the amount of offset increases from north to south toward the Duluth Complex. Three faults exhibit increased amounts of offset away from the Duluth Complex. Collectively, the relative motion along the majority of the faults indicate that they were formed (and reactivated?) during emplacement of the Duluth Complex. Five basaltic dikes occur within the mine area. Only one of the dikes occupies a fault zone; the remainder are intruded along various joint sets. The age of the dikes is inferred to be late-Duluth Complex. Several large-scale folds also occur within the mine area. They trend northwest and diminish in intensity away from the Complex, indicating that folding was initiated during emplacement of the Complex.University of Minnesota Duluth, Natural Resources Research Institute, 5013 Miller Trunk Highway, Duluth, MN 55811-1442; Funded by Minnesota Technology, Inc. and Northshore Mining Corporatio