Microstructural Analysis of Shear Zone Development in Gneiss. Rainy Lake Region Ontario, Canada
Mentor 1
Dyanna Czeck
Location
Union Wisconsin Room
Start Date
24-4-2015 10:30 AM
End Date
24-4-2015 11:45 AM
Description
Ductile shear zones are planar structures that accommodate deformation in rocks deep within tectonic belts. Similar to faults that form closer to the earth’s surface, shear zones allow rocks to slide past one another. Unlike faults, shear zones allow rocks to deform while maintaining cohesion. Typically, the rocks in the centers of the shear zones are deformed the most and deformation decreases to either side, forming a strain gradient. Analyzing microstructures present in shear zones can yield vital information about what small scale mechanisms were at play during deformation and which were responsible for the formation of shear zones in a given rock unit. To be able to analyze and identify microstructures within a rock, thin sections must be made. This is a tedious process in which the end result is a very thin sheet of rock (~30 microns thick) mounted on a glass slide that can be analyzed under a microscope. In this case, the area of interest is an example of small shear zones in gneiss collected from the Rice Bay Gneiss Dome in Ontario, Canada. The rocks in this region were deformed during tectonic plate collisions approximately 2.7 billion years ago, and the shear zones within these rocks formed as part of a sequence of structures that accommodated these collisions on the small scale. The shear zones are small bands within the gneiss, approximately 1 cm wide with reduced grain size and well-developed mineral alignments. Shear zone samples were collected and the rocks were cut so that a series of thin sections across the strain gradient could be analyzed. This microstructural analysis of shear zone development in the Rice Bay Gneiss Dome is part of ongoing research being conducted in the Rainy Lake Region of Ontario. All results of the analysis will be used to better understand shear zone development in this area and to learn how deformation was distributed between the different rock types of the Rainy Lake Region.
Microstructural Analysis of Shear Zone Development in Gneiss. Rainy Lake Region Ontario, Canada
Union Wisconsin Room
Ductile shear zones are planar structures that accommodate deformation in rocks deep within tectonic belts. Similar to faults that form closer to the earth’s surface, shear zones allow rocks to slide past one another. Unlike faults, shear zones allow rocks to deform while maintaining cohesion. Typically, the rocks in the centers of the shear zones are deformed the most and deformation decreases to either side, forming a strain gradient. Analyzing microstructures present in shear zones can yield vital information about what small scale mechanisms were at play during deformation and which were responsible for the formation of shear zones in a given rock unit. To be able to analyze and identify microstructures within a rock, thin sections must be made. This is a tedious process in which the end result is a very thin sheet of rock (~30 microns thick) mounted on a glass slide that can be analyzed under a microscope. In this case, the area of interest is an example of small shear zones in gneiss collected from the Rice Bay Gneiss Dome in Ontario, Canada. The rocks in this region were deformed during tectonic plate collisions approximately 2.7 billion years ago, and the shear zones within these rocks formed as part of a sequence of structures that accommodated these collisions on the small scale. The shear zones are small bands within the gneiss, approximately 1 cm wide with reduced grain size and well-developed mineral alignments. Shear zone samples were collected and the rocks were cut so that a series of thin sections across the strain gradient could be analyzed. This microstructural analysis of shear zone development in the Rice Bay Gneiss Dome is part of ongoing research being conducted in the Rainy Lake Region of Ontario. All results of the analysis will be used to better understand shear zone development in this area and to learn how deformation was distributed between the different rock types of the Rainy Lake Region.
