|Author:||Talla Takam et al., in preparation|
|Type area:||Léran Lake area (NTS sheets 23D11, 23D12 and 33A08)|
|Geological province:||Superior Province|
|Geological subdivision:||Opatica and Opinaca subprovinces|
Table des matières
The Wahemen Suite (nAwah) was introduced by Talla Takam et al. (in preparation) to describe undeformed intrusions of white-to-pinkish patina, medium to coarse-grained, locally pegmatitic and low in mafic minerals. These granite intrusions are located in the Léran Lake, Cadieux Lake and Bohier Island area.
The Wahemen Suite is massive, homogeneous, heterometric and non-magnetic. This unit has very low magnetic susceptibility on the residual total magnetic field map. It is leucocratic and very poor in mafic minerals (less than 3%). Grain contacts are gradual and diffuse, from medium to coarse to pegmatic. The Wahemen Suite contains quartz, plagioclase, K-feldspar, muscovite, moderately chloritized biotite and traces of garnet, tourmaline, chlorite, beryl and apatite. Garnets are microgranulitic and rounded (1 to 5 mm). They are either evenly distributed within the granite or aligned and preferentially associated with mica. Banding is magmatic in origin; this results in alternating centimetric to decametric medium-grained horizons in the form of bands very rich in garnet (1 and 3%), muscovite and tourmaline (<3%). In many places, granite has well-developed graphic structures that show the simultaneous crystallization of quartz and alkaline feldspar. Micrographic, perthitic and poecilitic microcline structures containing muscovite were observed in thin section. The pegmatic horizons are decametric to metric in thickness and contain rosette clusters of muscovite, biotite and quartz. The Wahemen Suite is a target lithology for Li, Be and Ta mineralizations. A 1-m3 pegmatite block in the Léran Lake area (outcrop 16-AB-1220) contains mica, garnet and spodumene as accessory minerals. Spodumene crystals are a few centimetres to three decametres long. In Quebec, the main lithium mineralizations are concentrated in Abitibi and in the Eeyou Istchee James Bay region; these mineralizations correspond to granitic pegmatites cutting Archean host rocks. In most cases, these pegmatites are genetically associated with peraluminous granitoids (S-type granite), as is the case with the Wahemen Suite.
The Wahemen Suite can be found in NTS sheets 23D11, 23D12, 33A07 and 33A08. The pluton was tracked for 65 km in an ENE-WSW direction. These intrusions are spatially associated with the borders of geological subprovinces in the Eeyou Istchee James Bay region. They generally mask contacts between the Opinaca and Opatica subprovinces.
The Wahemen Suite is one of the youngest Archean units in the Eeyou Istchee James Bay region. The U-Pb age on monazite obtained from a sample taken from sheet 23D12 (outcrop 16-ML-5175) indicates a crystallization age of 2640 ±10 Ma.
|Isotopic System||Mineral||Crystallization Age (Ma)||(+)||(-)||Reference(s)|
|U-Pb||Zircon||2640||10||10||Talla Takam et al., in preparation|
The Wahemen Suite is located to the north of the Upper Eastmain Greenstone Belt (UEGB). These intrusions cut the René Group volcanic rocks, the Bohier Group sedimentary rocks and the Laguiche Complex rocks. Near contact with the UEGB, granite of the Wahemen Suite may contain up to 30% sedimentary rock xenoliths (wacke, wacke paragneiss, metatexite and metaconglomerate) that are similar to the Bohier Group and Laguiche Complex rocks. Intrusion of the Wahemen Suite postdates several intrusive units, including the Misasque Suite and the Antons Granite.
Does not apply.