The Giton Complex was introduced in the Jeannin Lake area (Charette et al., 2016) to group heterogranular diatexites (ApPgit2) interpreted as circumscribed to a tectonic slice within the Rachel-Laporte Lithotectonic Domain. Hence it is a structural complex.

Migmatites of sedimentary origin of the Giton Complex include two informal units: migmatized paragneiss (ApPgit1) and heterogranular diatexite (ApPgit2).

Migmatized paragneiss of unit pPgit1 varies in composition from metapelite to meta-arenite to metawacke. Changes in the main minerals’ content locally induce banding. The amount of millimetric to centimetric leucosome bands fluctuates with the protolith (≤20%), increasing the banded appearance of the rock. Paragneiss is generally homogeneous and fine-grained. It is grey with a lighter alteration patina, locally beige to brownish. In thin sections, the matrix is well recrystallized. Micas (biotite and muscovite) make up 10-25% of the rock and form millimetric laminae marking foliation. Garnet commonly occurs as brown to pinkish crystals or porphyroblasts (1-5 mm). Staurolite locally occurs as small subhedral crystals within biotite and muscovite laminae. Accessory minerals (chlorite, opaque minerals, sphene, apatite, zircon and allanite) are also observed in small amounts. In places, actinolite forms felt clusters that preserve clinopyroxene cores. In some areas of unit ApPgit1, muscovite-biotite-garnet paraschist and garnet amphibolite form metric to hectometric layers.

Giton Complex 2 (pPgit2): Heterogranular Diatexite

Unit pPgit2 consists of homogeneous diatexite whose composition varies from granodiorite to quartz monzodiorite. The rock is heterogranular, yellowish to brownish grey, and shows a well-developed foliation associated locally with a protomylonitic texture. Diatexite regularly contains 15-30% centimetric phenocrystals of plagioclase and K-feldspar. It also includes 15-25% quartz and 5-20% microcline, interstitial or as phenocrystals. Silicate minerals float in a fine-grained matrix rich in brown biotite (20-40%) containing sphene and zircon inclusions. The rock also contains some hornblende (<5%), as well as zoisite and allanite. Plagioclase is slightly sericitized. Quartz displays undulatory extinction and partial recrystallization at the edge of larger crystals. Diatexite contains up to 10% centimetric to decimetric enclaves and layers (“schollen” or rafts) of variably migmatized biotite ± garnet paragneiss similar to that of unit ApPgit1. Certain metre-wide diatexite layers show greater deformation indicated by anastomosed foliation and the transformation of phenocrystals into sigmoid porphyroclasts associated with recrystallization tails.

Thickness and distribution

The Giton Complex is located in the southern portion of the Jeannin Lake area (Charette et al., 2016) where it forms a tectonic slice ~28 km long by 7 km wide and oriented NW-SE within the Rachel-Laporte Lithotectonic Domain. It covers an area of ~145 km².

Dating

The Paleoproterozoic age around 1829 Ma is similar to that obtained within diatexites of the Winnie Suite (~1838 Ma; Davis et al., 2015) of the Baleine Lithotectonic Domain. The presence of an inherited component around 2.12 Ga suggests that the Giton Complex is derived from the melting of Palaeoproterozoic metasedimentary rocks (Rayner et al., 2019).