|Author:||Moukhsil et al., 2015|
|Reference section:||Reference outcrops 14-AM-007 (mPbog1) and 14-TC-5022 (mPbog2)|
|Type area:||NTS sheet 32B02|
|Lithology:||Syenite, granite, websterite, gabbronorite|
Table des matières
The Bourguet Syenite was identified by Moukhsil et al. (2015) during mapping of the Parent region, Haut-Saint-Maurice.
This unit is the main facies of the Bourguet Syenite. It occupies the centre of the intrusion and consists of megacristic syenite with bluish grey K-feldspar phenocrystals (up to 4 cm long). It also contains magnetite, biotite, clinopyroxene, apatite and traces of ilmenite and titanite. K-feldspar phenocrystals are perthitic, contain apatite and biotite inclusions, and locally have Carlsbad twinning (orthose) without significant deformation. Phenocrystals display a slight preferential orientation, thus testifying to a magmatic texture of syenite. On the other hand, the host of the intrusion is highly deformed, developing mylonitization (shearing); straight and banded gneiss are observed.
Salmon-pink alkaline syenite dykes and minor amounts of websterite and granite are associated with this unit. Syenite dykes are fine-grained and cut the main facies. They are foliated and perthitic K-feldspar megaporphyric (40-65% of the rock, 1-3 cm long). Both types of dykes are composed of interstitial biotite, with small amounts of orthopyroxene, magnetite, ilmenite and apatite as accessory minerals. Websterite is green in fresh exposure, medium grained and contains clinopyroxene, orthopyroxene, biotite, olivine and green hornblende. Accessory minerals are apatite and ilmenite. Granite associated with syenite is pinkish and coarse grained. It is composed of quartz, plagioclase, K-feldspar, usually perthitic and opaque minerals.
This intrusion is roughly elliptical, approximately 7.5 km long and 4 km wide, with a NW-SE orientation. Two small intrusions are also visible northwest of the main intrusion.
Unit mPbog1 was dated during mapping of the Parent region and gave a crystallization age of 1038 +15/-13 Ma.
|Isotopic System||Mineral||Crystallization Age (Ma)||(+)||(-)||Reference(s)|
|U-Pb||Zircon||1038||15||13||Augland et al., 2016|
Does not apply.