Biteau Syenite
Stratigraphic label: [narc]bit
Map symbol: nAbit

First published: 15 May 2018
Last modified: 16 october 2019
























Translation of original French



Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
Author: Bandyayera and Daoudene, 2017
Age: Neoarchean
Reference section: None
Type area: Rodayer Lake area (NTS sheet 32K13)
Geological province: Superior Province
Geological subdivision: Opatica Subprovince
Lithology: Syenite
Type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active




The Biteau syenite is a lithodeme introduced by Bandyayera and Daoudene (2017) to describe an alkaline intrusion emplaced on the edge of the Lac Rodayer Pluton tonalitic basement, in the western Opatica Subprovince. The presence of syenite outcrops was first reported by Remick (1967) on the islands of Rodayer Lake. Subsequent geological mapping (Bandyayera and Daoudene, 2017) supported by geophysical surveys (D’Amours and Intissar, 2012) uncovered other small outcrops at Chaboullié Lake.



Petrographic analyses indicate that the Biteau Syenite consists of alkaline feldspar syenite, syenite, quartz syenite and monzonite. Alkaline feldspar syenite (>95% K-feldspar), containing clinopyroxene locally, accounts for more than 70% of the intrusion. The rock is light pink in altered and fresh surfaces, massive, homogeneous and coarse to very coarse grained. It contains cumulate and adcumulate facies, showing magmatic bedding characterized by alternating beds rich in centimetric K-feldspar crystals and beds rich to poor in ferromagnesian minerals. Quartz syenite and syenite are massive, medium to coarse grained and composed of hornblende-biotite-magnetite ± clinopyroxene. In thin section, they contain microcline, plagioclase, augite, hornblende, biotite, magnetite, and as accessory minerals, quartz, sphene, apatite and zircon. 

The Biteau Syenite also contains horizons of heterogeneous porphyraceous rocks, ranging in composition from monzonite to monzogabbro. Quartz content is generally <5%, but can reach 10% locally. K-feldspar is almost always present (up to 15%), while the percentage of ferromagnesian minerals varies between 15 and 35%. At the edge of the Biteau Syenite, a package of weakly foliated quartz diorite and diorite, medium-grained and containing 20-35% ferromagnesian minerals (hornblende and biotite) and 1% magnetite is locally observed. Finally, the Biteau Syenite contains metric enclaves of medium-grained foliated tonalite, probably coming from the Lac Rodayer Pluton, as well as enclaves of mafic and ultramafic rocks (pyroxenite and gabbro), medium to coarse-grained, interpreted as fragments detached from units of the Colomb-Chaboullié Group.

Geochemistry shows that the Biteau Syenite is distinguished by high contents of K2O (5.1-7.3 wt.%) and P2O5 (0.22-1.13 wt.%), as well as by some of the highest Ta/Yb ratios of intrusive rocks in the Rodayer Lake area. Syenite is also characterized by strong negative anomalies in Nb, Ta and Ti, and by a strong enrichment in light rare earths.


Thickness and Distribution

The Biteau Syenite intruded between the Rodayer Pluton tonalitic basement to the north and the Dusaux Gneissic Complex to the south. It is associated with a strong WNW-oriented positive magnetic anomaly, clearly circular at Rodayer Lake, extending for 18 km long and 3 km wide. The majority of the intrusion occurs under Rodayer and Chaboullié lakes, while the most representative outcrops of this unit were observed on islands of southeastern Rodayer Lake and at the southern end of Chaboullié Lake (Remick, 1963).



A sample of homogeneous coarse-grained syenite, showing magmatic bedding and K-feldspar cumulate beds, was taken for U-Pb dating. Analyses as a whole yielded an age of 2693.6 ±4.6 Ma (David, 2018), interpreted as the age of intrusion of the Biteau Syenite.

Unit Sample Number Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
nAbit 2015-AN-3135A U-Pb Zircon 2693.6 4.6 4.6 David, 2018

Stratigraphic Relationship(s)

The Biteau Syenite is one of the oldest post- to late-tectonic intrusions in this part of the Opatica Subprovince (2697-2618 Ma; Moukhsil et al., 2003). It cuts rocks of the Lac Rodayer Pluton (2823 Ma; Davis et al., 1995), Dusaux Complex and Desorsons Intrusion (2729.8 Ma; David, 2018), as well as the Colomb-Chaboullié Group volcano-sedimentary assemblage. Regionally, the Biteau Syenite appears contemporary to the Short Lake carbonatite (2691.6 +5/-3 Ma) and Berthiaume Syenite (2687.9 ±1.2 Ma; Davis et al., 2005).


Does not apply.


Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
BANDYAYERA, D. – DAOUDENE, Y. Géologie de la région du lac Rodayer (SNRC 32K13-32K14-32N03 et 32N04-SE). Ministère de l’Énergie et des Ressources naturelles, Québec; RG 2017-01, 60 pages. 2017 RG 2017-01
D’AMOURS, I. – INTISSAR, R. Levé magnétique aéroporté dans le secteur du lac Evans, Baie-James. Ministère des Ressources naturelles et de la Faune, Québec; DP 2012-01, 8 pages, 66 plans. 2012 DP 2012-01
MOUKHSIL, A. – LEGAULT, M. – BOILY, M. – DOYON, J. – SAWYER, E. – DAVIS, D.W. Synthèse géologique et métallogénique de la ceinture de roches vertes de la Moyenne et de la Basse-Eastmain (Baie-James). Ministère des Ressources naturelles, de la Faune et des Parcs, Québec; ET 2002-06, 57 pages. 2003 ET 2002-06

Datation U-Pb dans la Province du Supérieur effectuées au GEOTOP en 2015-2016. Ministère de l’Énergie et des Ressources naturelles, Québec; MB 2018-16, 24 pages.

2018 MB 2018-16
REMICK, J.H. Géologie de la région de Colomb-Chaboullié-Fabulet, Territoire d’Abitibi. Ministère des Richesses naturelles, Québec; RP 514, 29 pages, 3 plans. 1963 RP 514



16 octobre 2019