The Evelyn Creek–Mount Grant area includes a large region of igneous and meta-igneous rocks; here termed the Mount Grant batholith. The batholith comprises mostly deformed Mississippian metatonalite of the Simpson Range suite and variably, but mostly non-deformed Cretaceous granitic rocks of the Cassiar suite. The metatonalite has a sheet-like geometry and is in contact with contrasting metasedimentary successions. Overlying the metatonalite is the Slate Mountain succession, which includes quartzite, psammite, phyllite and limestone. The metatonalite overlies rocks of the Evelyn Creek succession (new), which has a tripartite stratigraphy; its lower part is dominated by chert and siliceous argillite, the middle unit comprises chlorite-muscovite schist and quartzite, while the upper unit is a prominent interval of pale coloured marble/calcsilicate. The contact between the Evelyn Creek succession and the overlying Mississippian metatonalite is interpreted to be structural rather than intrusive. Rocks of the Cassiar suite include large volumes of non-deformed granite and quartz monzonite and lesser amounts of foliated equivalents. Low pressure metamorphism is recorded by andalusite and/or sillimanite bearing schists that are restricted to the eastern part of the area. This metamorphism and deformation did not affect the remainder of the area, where latest penetrative structures are crosscut by Early Jurassic rocks of the Lokken suite.