The intrusion was first named “Muscocho Stock” by Holmes (1959) and Hébert (1979), and later named “Muscocho Pluton” by subsequent authors (Racicot et al., 1984; Daigneault, 1991; Tait, 1992).

According to Tait (1992, p. 43): “It consists of a hornblende granodiorite. The rock is very homogeneous and pink-grey. There are a few more mafic enclaves distributed mainly on the pluton’s edges. Primary foliation, represented by the preferential alignment of tabular hornblende and plagioclase phenocrystals, forms a more or less concentric structure within the pluton. There is an extremely well developed diaclase system, the spacing of which, in places, is in the order of a millimetre. A prominent feature of this granitoid mass is the absence of planar structures that can be correlated with regional schistosity. Contact metamorphism produced an aureole that spreads between 500 and 1000 m through the host volcanics. Very close to contact, rocks reach the amphibolite facies, where the garnet-hornblende-plagioclase paragenesis is observed. Regional schistosity (S₂) around the intrusive mass’s edges is destroyed by recrystallization associated with contact metamorphism, which overprints regional metamorphism, confirming the late emplacement of the pluton. The presence of apophysis granodiorite dykes, derived from the pluton and that cut regional schistosity, also confirms this relationship. These dykes are becoming more abundant as we approach the plutonic mass.”