ReConstructing a Jigsaw Puzzle - Smashed by Continents Over Millions Of YEars
The structural geology of Thor is quite complicated, but it is the most important control on mineralization in combination with the lithologies.
Thor Fault Zone ('TFZ')
The structural geology is dominated by a large NNW-trending feature called the Thor Fault Zone. This feature dips moderately to the ENE (45 degrees). Virtually all of the economic mineralization of interest lies within this structural corridor, or the associated splays. The Thor Fault Zone extends throughout the entire Thor property. And its full extent of the fault is currently unknown.
Much of the motion on this fault is strike lateral in nature as evidenced by slickensides within the fault zone, but these can vary on a local basis. It is also evident that the east side of the fault has dropped down several hundred meters.
The Folding at Thor is dominated by one single phase of folding. This folding predates the Thor Fault Zone and is oriented in a northwest direction. All of the folding is isoclinal in nature, and in places it can be very tight.
To the east of the Thor Fault Zone, a single large anticline (Thor Anticline) can be found and this controls much of the topography and localization of the True fissure and Broadview Creeks. To the west of the Thor Fault Zone the topography is controlled by the tight folding in the Broadview and Sharon Creek Formations, and it can be seen that the axis of the folds have been deformed by movement along the Thor Fault Zone.
Structural and Lithological Control on Mineralization
Mineralization within the Thor fault Zone is spatially related to the contact between the underlying Sharon Creek Formation and the overlying Broadview Formation. Because the location of this contact has been folded in a northwest trending direction, geological mapping is critical in locating this contact. Where this contact between the Sharon Creek/Broadview Formation comes into contact with the Thor Fault Zone, the lowest part of the Broadview Formation is mineralized. This contact is preserved in the rocks found to the east of the Thor Fault Zone at Thor, and to the west rocks of the non-receptive Sharon Creek Formation are generally found.
1,072 bedding surface measurements were taken at Thor within the Broadview Creek, Jowett and Sharon Creek Formations. This data was then plotted as poles to bedding on the figure to the left and show that there is only one phase of folding.
The stereonet shows that the bedding is folded around an axis that trends northwesterly, and it is calculated to strike 310.5 degrees and plunges to the northwest at 49.7 degrees. The axial plane is calculated at 305.1 degrees and it deeps steeply to the northeast with a dip of 85.4 degrees.
Plunge of Folds (F1)
The plunge of the folds was also measured in the field, and this shows a very close resemblance to the the calculated fold plunge from the bedding planes (right figure),
This data shows a very tight cluster that is in the expected position based on the S0 surfaces. One of the interesting features is a small cluster of points plunging to the southeast that is normal to the main cluster of points.
Top of Vein (V1)
Typically, the top of the mineralized zones at Thor is encountered in drill holes, but there are several places where it is exposed at surface, particularly the Scab Zone. A total of 171 locations were measured in a wide variety of areas at Thor, and the stereonet for the poles to this surface is shown to the left The following conclusions can be made: