The Sarane Metagabbro was defined by Gigon and Goutier (2017) following the 2013 fieldwork. The unit’s name corresponds to the first name of the geologist involved in the discovery of this unit, given the scarcity of toponymic elements in this area.

The Sarane Metagabbro is a mafic unit consisting mainly of amphibolite derived from gabbro (Gigon and Goutier, 2017). The rock is fine to medium grained and has a white and green alteration patina and fresh surface. It is sparsely foliated. In thin section, the magmatic texture is generally recognizable, but metamorphism and deformation have resulted in partial recrystallization of the rock with the formation of a heterogranular polygonal texture. Primary pyroxenes are thus transformed into amphibole aggregates. Some horizons are much more deformed and show mylonitic or banding textures.

Amphibolite contains hornblende (30–40%) and plagioclase (60–70%), local pyrite (<3%) and minor amounts of magnetite, biotite, epidote and tremolite. The unit also locally contains horizons of various compositions:

• anorthositic horizons containing amphibole (<10%), altered to calcite and muscovite, mineralized in chalcopyrite, pyrite and malachite;
• centimetric horizons of muscovite-biotite-pyrite gabbro;
• a metric dark green horizon consisting of magnetite-pyrite-chalcopyrite-malachite amphibolite;
• a decimetric horizon of amphibolite derived from leucoxene-pyrrhotite-pyrite gabbro;
• amphibolite derived from diorite and quartz diorite.

In addition, several centimetric enclaves of hornblendite or metapyroxenite were observed locally in dioritic amphibolite (outcrop 2013-JJ-6523).