page_title: Temagami Greenstone Belt
section_title: Deformation zones
hierarchical_section_title: Temagami Greenstone Belt / Geology / Deformation zones
caption_attribution_description: English: Map of lakes, deformation zones, volcanic complexes and the Chambers-Strathy Batholith in Strathy Township, Temagami, Ontario, Canada.
context_page_description: The Temagami Greenstone Belt is a small 2.7 billion year old greenstone belt in the Temagami region of Northeastern Ontario, Canada. It represents a feature of the Superior craton, an ancient and stable part of the Earth's lithosphere that forms the core of the North American continent and Canadian Shield. The belt is composed of metamorphosed volcanic rocks that range in composition from basalt to rhyolite. These form the east-northeast trend of the belt and are overlain by metamorphosed sedimentary rocks. They were created during several volcanic episodes involving a variety of eruptive styles ranging from passive lava eruptions to viscous explosive eruptions.
  Part of the Canadian Shield, the TGB contains some of the oldest known rocks on Earth. The belt is made up of a number of geologic features such as batholiths, stocks, dikes, volcanic complexes, layered intrusions and deformation zones. These are situated in several geographical townships in the municipality of Temagami, including Chambers, Strathy, Strathcona, Briggs and possibly Best.
context_section_description: Many north-trending shear zones intersect iron-rich tholeiitic basalts of the Arsenic Lake Formation. These zones range in width from less than 1 m (3.3 ft) up to 5 m (16 ft), and might maintain a larger area of weakness that was tectonically active over the past billion years. Evidence for early tectonism, likely related to volcanic activity, include the greater density of felsic dikes concentrated immediately around these zones. An example is the north-south trending Big Dan Shear Zone situated near the former garbage dump of Temagami. The felsic dikes near this zone are interpreted to represent a subvolcanic feeder system to the overlying felsic volcanic rocks. It is probable that the dikes maintained a former zone of weakness now demonstrated by the shear zones. Renewed tectonic activity along the Big Dan Shear Zone is manifested by offset of clastic sediments east of the Ontario Northland Railway. This phase of tectonic activity displaced felsic dikes north of the exposed part of this shear zone. However, considerable displacement of the dikes at this location is unknown. The most recent phase of tectonic activity along the Big Dan Shear Zone resulted in the displacement of a Proterozoic dike composed of diabase, which intersects the zone. A similar abundance of felsic dikes are adjacent to Arsenic Lake just west of Highway 11, indicating similar repetitive tectonism also occurred along that structural zone. Therefore, the north-trending shear zones may have been active for at least a billion years.
  Extending from Net Lake to Vermilion Lake lies a northeast-southwest trending high strain zone known as the Net Lake-Vermilion Lake Deformation Zone. Because geologic mapping has not been done comprehensively throughout this zone, its exact width is unknown. The expression of this deformation zone is clearly identifiable by the intense change in volcanic rocks of the TGB. Volcanic units comprising the northwestern portion of the shear zone have shifted to the northeast while the volcanic rocks comprising its southeastern portion have shifted to the southwest. Along the northeastern arm of Lake Temagami in Strathcona Township lies the Northeast Arm Deformation Zone. This northeast-trending shear zone has not been studied in detail, but casual studies of many islands along the northeastern arm of Lake Temagami have shown that there is severe foliation and minor ferroan carbonate across an area about 1 km (0.62 mi) wide. The Link Lake Deformation Zone, also known as the Link Lake Shear Zone, is an area of deformation 0.5 km (0.31 mi) wide and over 3 km (1.9 mi) long in Strathy Township. It extends through Link Lake to east of Highway 11, but it is uncertain whether it extends west of Link Lake because no expression of it has been found in the Sherman Mine area. Therefore, the Link Lake Shear Zone might be a northern extension of the Northeast Arm Deformation Zone further south. Strain intensity of the Link Lake Shear Zone is diverse. Generally, the greatest strain intensity is throughout pyroclastic rocks. Extending from the western boundary of central Chambers Township through Tasse Lake to the east is the Tasse Lake Deformation Zone. This deformation zone is roughly 3 km (1.9 mi) long and at least 0.5 km (0.31 mi) wide. It is uncertain if this deformation zone extends east of Tasse Lake.
caption: Lakes, volcanic complexes and deformation zones of Strathy Township. Also shown are portions of the massive Chambers-Strathy Batholith
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