|Author:||Bandyayera and Daoudene, 2018|
|Type area:||The most representative outcrops are in the southern half of the Nemiscau Lake region (NTS sheet 32N07).|
|Geological province:||Superior Province|
|Geological subdivision:||Nemiscau Subprovince|
|Lithology:||Felsic intrusive rocks and migmatite|
Table des matières
The first descriptions of the rocks assigned to the Mezières Suite were drawn from the works of Remick (1963) and Gillain (1965). The name Mezières Suite, whose namesake lake is located in the NTS sheet 32N06, was introduced by Bandyayera and Daoudene (2018) following the summer 2017 work in the Lake of La Sicotière region (sheet 32N08).
The Mezières Suite consists of white biotite ± garnet ± muscovite granitic pegmatite, locally pinkish beige. The rock is massive to locally foliated and heterogranular. The typical graphic texture is characterized by the presence of quartz laths oriented parallel to cleavage in large K-feldspar crystals. This unit is distinguished by the rarity of tourmaline, which is normally present in other white pegmatites in the region. The rock contains biotite (up to 10%), muscovite (up to 5%), garnet (1-5%) and magnetite grains disseminated or in centimetric clusters.
The Mezières Suite contains 2 to 20% metric to decametric paragneiss enclaves, which are generally boudinaged and resemble in places to partially digested restites. Contacts between enclaves and the pegmatic host rock usually show a biotite rim. The Mezières Suite is interpreted as the final product of partial melting of metasedimentary rocks of the Rupert Complex.
From a geochemical point of view, rocks of the Mezières Suite are S-type, peraluminous, of calcic to calc-alkaline affinity.
The Mezières Suite is composed of several intrusions of varying sizes scattered over an area about 130 km long by 100 km wide.
A sample from an intrusive pegmatitic biotite granite in migmatitized paragneiss from the Nemiscau Subprovince on the Broadback River shore (sheet 32N03) yielded an age of intrusion of 2672 ±2 Ma (Davis et al., 1995). Another sample located on the La Marte River shore (sheet 32N08) taken in situ in a diatexite derived from partial melting of a garnet paragneiss yielded a crystallization age of 2691 ±5.9 Ma (David, personal communication). This S-type diatexite is interpreted as contemporaneous and genetically associated with garnet-muscovite pegmatites of the Mezières Suite. These data indicate that pegmatites in the Mezières Suite are polyphased intrusions emplaced between 2691 and 2672 Ma.
|Isotopic System||Mineral||Crystallization Age (Ma)||(+)||(-)||Reference(s)|
|U-Pb||Zircon||2691||5.9||5.9||David, personal communication|
|U-Pb||Zircon||2672||2||2||Davis et al., 1995|
The Mezières Suite is usually interstratified with rocks of the Rupert Complex and cuts them locally. The white pegmatite that cuts the Lac des Montagnes Group is also part of this unit.
Does not apply.