Temagami Greenstone Belt 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
Geology of Wisconsin and metavolcanics formed first, followed by granites more than 2.7 billion years ago. The rock record contains an uncertain age gap with younger 2.3 billion year old Proterozoic quartzofeldspathic and migmatite gneiss, with amphibolite and biotite schist. Around 1.9 billion years ago, mafic, intermediate and felsic rocks, in some cases with subordinate metasedimentary rocks, began to form and metamorphosed, reaching greenschist and amphibolite grade on the sequence of metamorphic facies. The Ironwood and Riverton Iron formations are recognized from aerial magnetic surveys. Metamorphosed argillite, quartzite, greywacke conglomerate and marble with small areas of interbedded metavolcaic rocks make up the Tyler