Rocks of the Martel Suite were originally part of the Lac Barou Massif described by Hocq (1985). This massif was divided into several units by Beauchamp et al. (2018) following mapping work conducted by the Ministère. They separated rocks of the Martel Pluton which, unlike other granites of the Otish Mountains, have a banded appearance and contain more sericite. Because two intrusive masses were identified in sheets 33A01 and 33A02, the Martel Pluton became the Martel Suite (Beauchamp, 2020).

The Martel Suite entirely consists of fairly light grey-white granite, locally greenish in altered surface and light pinkish white in fresh exposure. This granite is medium to coarse-grained, massive to slightly foliated, with pegmatitic clusters in places. The Martel Suite is distinguished from other granites in the area by its white mica content and the resulting banded appearance. Indeed, the Martel Suite granite contains quartz, microcline, abundant plagioclase and 1 to 4% well-crystallized muscovite flakes. In thin sections, muscovite is locally observed as intergrowth with chlorite or biotite forming symplektitic bundles, which marks rapid and primary crystallization. White mica also appears as veinlets. These veinlets actually represent fractures opened during a brittle deformation event and later filled with secondary sericite±chlorite±biotite. At the microscopic scale, it is clear that mica veinlets cut quartz and feldspar crystals. Early ductile deformation is also marked by undulatory extinction of quartz. The rock also contains 1 to 2% millimetric red to black euhedral garnet and ~1% biotite. In some cases, garnet crystals are either randomly distributed or aligned with magmatic banding. In thin section, garnet is poikiloblastic and altered to chlorite ± sericite. It is not uncommon to see a graphic texture on outcrop. The main alterations are weak to moderate hematitization and damouritization, both of which affect plagioclase. The Martel Suite contains many enclaves of Laguiche Complex migmatized paragneiss (nAlgi2c). Granitic pegmatites clearly cut rocks of Martel Suite.

From a geochemical perspective (Beauchamp, 2020), the composition of Martel Suite rocks is very homogeneous and characterized by low content in Fe₂O_3T (0.44-1.27%) and MgO (0.03-0.14%) as well as higher K₂O content (3.61-6.8%) than other felsic intrusions of the area. Regarding trace elements, samples analyzed are distinguished by their very low contents in Sr (13-61 ppm), Ba (26-175 ppm) and V (below the detection limit). The Martel Suite is peraluminous and similar to S-type iron-rich granitoids (Maniar and Piccoli, 1989; Frost et al., 2001). Rocks are calc-alkaline to alkaline in affinity (Frost et al., 2001). The rare earths diagram is arched, V-shaped and has a large negative Eu anomaly (Palme and O’Neill, 2004). The profiles show a slight enrichment in heavy rare earth elements because of garnet in the rock. Very strong negative anomalies in Nb, Ce, Ti, and positive anomalies in Th P, and Hf appear on the spider diagram normalized to the primitive mantle (McDonough and Sun, 1995).