|Author:||Bandyayera and Daoudene, 2018|
|Type area:||La Sicotière Lake area (NTS sheet 32N08)|
|Geological province:||Superior Province|
|Geological subdivision:||Nemiscau and La Grande subprovinces|
|Lithology:||Intrusive granitic rocks|
Table des matières
The granitic rocks of the Kaupanaukau Suite were part of the Champion Complex, a large polyphase intrusive mass located south of the Eastmain Group, and constituted the southern extension of the La Grande Subprovince (Card and Ciesielski, 1986). The name “Kaupanaukau Suite” was introduced by Bandyayera and Daoudene (2018) following the summer 2017 mapping campaign. This suite includes all of the late granitic rocks in the Champion Lake area that belong to the La Grande and Nemiscau subprovinces (Bandyayera and Daoudene, 2016; Bandyayera and Daoudene, in preparation).
The Kaupanaukau Suite consists of a package of granitic intrusions and granitic pegmatite that cut all the other Archean rocks in the region. It consists of three units: a pink biotite ± magnetite granite unit (nAkup1), a pink pegmatite and granite unit (nAkup2) and a pink granitic pegmatite unit (nAkup3).
The nAkup1 unit occurs as decametric to kilometric intrusions in the Rupert Complex and the Champion Complex. It consists of massive biotite ± magnetite granite, homogeneous, heterogranular and low to highly magnetic. In places, the rock has a granodioritic composition. The nAkup1 unit is very poor in ferromagnesian minerals (<5%) and contains no garnet. The principal minerals are quartz, plagioclase, partially chloritized biotite (<5%) and magnetite (1-8%). Accessory apatite and zircon are observed in thin section.
Geochemically, these granite intrusions are typically peraluminous, type I and syncollisional.
The nAkup2 unit consists of a package of granitic pegmatite (Akup3 unit) and biotite ± magnetite granite, which are non-mappable separately at a 1:50,000 scale. Grain size contacts are generally gradual and diffuse, from medium and coarse-grained to pegmatitic, and locally sharp, showing intrusion of pegmatite into granite.
The nAkup3 unit consists of pale pink granitic pegmatite with a graphic structure. The rock is magnetic and has a massive and heterogranular appearance, as well as locally visible bedding or pegmatitic zoning. It regularly contains centimetric clusters of K-feldspar (up to 5 cm) cemented by quartz. Pegmatite has well-developed graphic and perthitic textures. Granitic pegmatite is also distinguished by a low content of ferromagnesian minerals representing less than 5% of the rock. The rock contains no garnet and rarely tourmaline. The nAkup3 unit contains enclaves of all other units of the Champion Complex. South-east of the Nemiscau Lake region (sheet 32N07), between the Rupert River and Nemiscau Lake, a kilometric pink pegmatite intrusion assigned to the nAkup3 unit contains up to 20% of paragneiss-derived migmatite enclaves originating from the surrounding supracrustal rocks of the Rupert Complex.
The various units in the Kaupanaukau Suite are elongated and are up to 15 km long and 2 km wide. In places, they form small rounded masses ranging from 1.5 to 2 km in diameter.
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