The TGB consists of two large volcanic sequences that were formed during several phases of volcanic activity.
These two sequences, known as the Older and Younger volcanic complexes, consist of volcanic rocks ranging in composition from felsic to mafic.
The Older Volcanic Complex is composed mainly of felsic lava flows and pyroclastic deposits with smaller amounts of mafic volcanic rocks.
It underlies a large portion of northwestern Strathy Township and is penetrated by mafic intrusions, although the Kanichee Intrusion consists of peridotite and pyroxenite, which are ultramafic rocks.
Just to the southeast, the Younger Volcanic Complex consists mainly of mafic volcanic rocks that form four geologic formations.
The Arsenic Lake Formation is composed of dark green, iron-rich, massive and pillowed tholeiitic basalts.
Throughout the Arsenic Lake Formation are feldspar-phyric basaltic lava flows.
This type of basalt contains tabular feldspar phenocrysts that range up to 2 cm (0.79 in) in cross section.
Both pillowed and massive lava flows have been known to contain coarse feldspar.
Coarse feldspar-bearing, iron tholeiitic basalts are more common east of Highway 11.

A number of volcanic rocks comprise the Link Lake Formation, such as feldspar-phyric, calc-alkaline basalt and andesite lava flows and less abundant quartz and quartz-feldspar-phyric felsic lava flows.
Feldspar-phyric basalt lava flows are normally pillowed.
Pyroclastic deposits, quartz-phyric and feldspar-felsic rocks are also present.
The largest of the less common felsic lava flows is located between Link Lake and Turtle Lake.
It is 2.5 km (1.6 mi) long and less than 200 m (660 ft) thick.
The thickest portion of this lava flow or dome is located at the western end of Link Lake, where it is likely associated with a volcanic vent.
The bulk of felsic rock in the Link Lake Formation occurs as subaqueous pyroclastic flow deposits.
Subearial pyroclastics are normally quartz-phyric and range up to 30 cm (12 in) in crosssection.
Dark green subearial pyroclastics composed of chlorite and sericite are uncommon and have sustained preferential compression in response to shear throughout the Link Lake Deformation Zone.
These dark compressed pyroclastics have been interpreted to be pumice.
Some of the subsequence pyroclastic deposits contain fragments of pyrite and quartz, suggesting that discharged sulfide hydrothermal activity took place throughout the volcanic source area.

Resedimented felsic, epiclastic and turbiditic sediments compose the Turtle Lake Formation.
The base of this formation consists of a heterolithic, volcaniclastic, matrix-supported conglomerate unit that overlies felsic lava flows and pillowed, calc-alkaline basalts of the Link Lake Formation.
Many rounded to subangular felsic and mafic volcanic fragments are known to occur in the unit, as well as rare quartz vein fragments and one fragment of white chert.
The conglomerate unit passes laterally and vertically into thin bedded deposits.
These thin bedded deposits are interpreted to be turbidites that originated from a felsic volcanic vent at the western end of Link Lake.
Many dark green, highly vesicular, iron-rich tholeiitic basalts occur in the Turtle Lake Formation, and are interbedded with thin-bedded wackes on the southern limb of the Tetapaga Syncline.
The basalts are best exposed along the south shore of Turtle Lake.
In some cases, the basalt vesicles are over 1 cm (0.39 in) in diameter and are now filled by white quartz.

A series of dark green, massive and pillowed iron-rich tholeiitic basalt lava flows compose an unnamed upper volcanic formation of the Younger Volcanic Complex.
It is situated in the core of the Tetapaga Syncline.
Not much is known about this volcanic formation because only a small portion of it remains exposed in western Strathy Township.
The TGB consists of two large volcanic sequences that were formed during several phases of volcanic activity. These two sequences, known as the Older and Younger volcanic complexes, consist of volcanic rocks ranging in composition from felsic to mafic. The Older Volcanic Complex is composed mainly of felsic lava flows and pyroclastic deposits with smaller amounts of mafic volcanic rocks. It underlies a large portion of northwestern Strathy Township and is penetrated by mafic intrusions, although the Kanichee Intrusion consists of peridotite and pyroxenite, which are ultramafic rocks. Just to the southeast, the Younger Volcanic Complex consists mainly of mafic volcanic rocks that form four geologic formations. The Arsenic Lake Formation is composed of dark green, iron-rich, massive and pillowed tholeiitic basalts. Throughout the Arsenic Lake Formation are feldspar-phyric basaltic lava flows. This type of basalt contains tabular feldspar phenocrysts that range up to 2 cm (0.79 in) in cross section. Both pillowed and massive lava flows have been known to contain coarse feldspar. Coarse feldspar-bearing, iron tholeiitic basalts are more common east of Highway 11.
A number of volcanic rocks comprise the Link Lake Formation, such as feldspar-phyric, calc-alkaline basalt and andesite lava flows and less abundant quartz and quartz-feldspar-phyric felsic lava flows. Feldspar-phyric basalt lava flows are normally pillowed. Pyroclastic deposits, quartz-phyric and feldspar-felsic rocks are also present. The largest of the less common felsic lava flows is located between Link Lake and Turtle Lake. It is 2.5 km (1.6 mi) long and less than 200 m (660 ft) thick. The thickest portion of this lava flow or dome is located at the western end of Link Lake, where it is likely associated with a volcanic vent. The bulk of felsic rock in the Link Lake Formation occurs as subaqueous pyroclastic flow deposits. Subearial pyroclastics are normally quartz-phyric and range up to 30 cm (12 in) in crosssection. Dark green subearial pyroclastics composed of chlorite and sericite are uncommon and have sustained preferential compression in response to shear throughout the Link Lake Deformation Zone. These dark compressed pyroclastics have been interpreted to be pumice. Some of the subsequence pyroclastic deposits contain fragments of pyrite and quartz, suggesting that discharged sulfide hydrothermal activity took place throughout the volcanic source area.
Resedimented felsic, epiclastic and turbiditic sediments compose the Turtle Lake Formation. The base of this formation consists of a heterolithic, volcaniclastic, matrix-supported conglomerate unit that overlies felsic lava flows and pillowed, calc-alkaline basalts of the Link Lake Formation. Many rounded to subangular felsic and mafic volcanic fragments are known to occur in the unit, as well as rare quartz vein fragments and one fragment of white chert. The conglomerate unit passes laterally and vertically into thin bedded deposits. These thin bedded deposits are interpreted to be turbidites that originated from a felsic volcanic vent at the western end of Link Lake. Many dark green, highly vesicular, iron-rich tholeiitic basalts occur in the Turtle Lake Formation, and are interbedded with thin-bedded wackes on the southern limb of the Tetapaga Syncline. The basalts are best exposed along the south shore of Turtle Lake. In some cases, the basalt vesicles are over 1 cm (0.39 in) in diameter and are now filled by white quartz.
A series of dark green, massive and pillowed iron-rich tholeiitic basalt lava flows compose an unnamed upper volcanic formation of the Younger Volcanic Complex. It is situated in the core of the Tetapaga Syncline. Not much is known about this volcanic formation because only a small portion of it remains exposed in western Strathy Township.
Temagami Greenstone Belt