Mount Meager massif are covered with their eruptive products and serve as the surface expressions of intrusions. As a result, they provide a unique opportunity to study the relationships between magma chambers and their lavas. The mafic (rich in magnesium and iron), intermediate (between mafic and felsic) and felsic (rich in feldspar and quartz) volcanic rocks of the massif were erupted from at least eight volcanic vents. The Bridge River Vent is a relatively young volcanic crater that formed during an eruption about 2,400 years ago. This eruption ranged in character from explosive to effusive and involved lava dome extrusion, pyroclastic flows, lahars
Eoarchean geology highly deformed biotite-hornblende tonalitic to granitic orthogneiss. Subordinate mafic amphibolitic and chloritic elliptical enclaves and inclusions are observed in felsic gneisses.Although the rocks are highly deformed and could not reflect the original field relation between rock units, the chemical composition of the rocks showcases how Eoarchean greenstone-TTG be like. Chemical composition in the mafic inclusion suggests the acasta area was possibly a supra-subduction setting. Dominant felsic rocks are composed of highly deformed tonalitic, granodioritic and granitic gneisses. Inclusion of as early as 4.2 billion years old zircon core are observed in the gneisses. Mafic rocks, i.e. subordinate amphibolite and ultra