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Lépante Suite
Stratigraphic label: [narc]lpn
Map symbol: nAlpn
 

First published: 4 December 2020
Last modified:

 

 

 

 

 

 

 

 

 

 

 

 

 

  DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail. 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
None
 
Author: Beauchamp, 2020
Age: Neoarchean
Stratotype: None
Type area: Cadieux Lake area (NTS sheets 33A02, 33A07 and 33A08)
Geological province: Superior Province
Geological subdivision: Opinaca Subprovince
Lithology: Quartz monzodiorite, monzodiorite and diorite
Category: Lithodemic
Rank: Suite
Status: Formal
Use: Active

 

 

 

 

Background

The Lépante Suite (nAlpn) was introduced by Beauchamp (2020) to describe intermediate intrusive rocks superimposed on an area of moderate magnetic susceptibility in the Eastmain-Sorbier Shear Zone, in the Cadieux Lake area.

 

 

 

Description

Because there are few outcrops in the area, the following description is based on a limited number of observation stations. The Lépante Suite is homogeneous, medium grained and foliated. It consists of quartz monzodiorite, diorite and granodiorite. The rock is white-grey with black spots in altered surface and fresh exposure. It is composed of 5 to 20% quartz and 10 to 20% ferromagnesian minerals. Hornblende is consistently more abundant than biotite. The rock is highly magnetic due to the presence of magnetite. In thin section, minerals observed are sphene (≤1%), epidote (pistachite, allanite), apatite, zircon and rutile.

 

 
Rocks of the Lépante Suite are intruded by a pinkish-white granite that forms layers subparallel to the Sn foliation. These intrusions are very straight and locally boudinaged. The Lépante Suite contains a few granoblastic diorite enclaves that are highly stretched in the Sn foliation direction.
 

Geochemical analyses of samples collected during summer 2018 mapping (Beauchamp, 2020) indicate that the Lépante Suite is a magnesian granitoid of alkaline-calcic to calc-alkaline affinity (Frost et al., 2001). It is generally metaluminous and type I (Maniar and Piccoli, 1989). In the diagram of Pearce et al. (1984), samples plot in the field of volcanic arc granites. The rare earth diagram normalized to CI chondrite (Palme and O’Neill, 2004) shows a slight light rare earth enrichment compared to heavy rare earths. Finally, negative anomalies in Nb, Ta, P and Ti, and positive in La, Ce and Nd are present on spider diagrams.

 

 

 

Thickness and Distribution

The Lépante Suite is located in the Cadieux Lake area (sheets 33A02, 33A07 and 33A08). The main intrusion is mostly longitudinal, 20 km long and 0.5 km to 3 km thick. Other small intrusive masses outcrop in the Eastmain-Sorbier Shear Zone.

Dating

None.

Stratigraphic Relationship(s)

Rocks of the Lépante Suite cut paragneiss of the Laguiche Complex. At the macroscopic and microscopic scales, the Lépante Suite closely resembles rocks of the Macleod Batholith. It is possible that these two intrusive bodies are related and have similar ages.

Paleontology

Does not apply.

References

Publications Available Through Sigéom Examine

BEAUCHAMP, A.-M. 2020. Géologie de la région du lac Cadieux, sous-provinces d’Opatica et d’Opinaca, Eeyou Istchee Baie-James, Québec, Canada. MERN. BG 2019-02, 2 plans.

 

 

 

Other Publications

FROST, B.R., BARNES, C.G., COLLINS, W.J., ARCULUS, R.J., ELLIS, D.J., FROST, C.D. 2001. A geochemical classification for granitic rocks. Journal of Petrology; volume 12, numéro 11, pages 2033-2048. doi.org/10.1093/petrology/42.11.2033.

MANIAR, P.D., PICCOLI, P.M. 1989. Tectonic discrimination of granitoids. Geological Society of America Bulletin; volume 101, pages 635–643. doi.org/10.1130/0016-7606(1989)101<0635:TDOG>2.3.CO;2.

MCDONOUGH, W.F., SUN, S.S. 1995. The composition of the earth. Chemical Geology; volume 120, pages 223-253. doi.org/10.1016/0009-2541(94)00140-4.

PALME, H., O’NEILL, H.S.C. 2004. Cosmochemical estimates of mantle composition. In Treatise on Geochemistry. (Holland, H.D. and Turrekian, K.K. editors), Elsevier, Amsterdam, The Netherlands; volume 2, pages 1–38. doi.org/10.1016/B978-0-08-095975-7.00201-1.

PEARCE, J.A., HARRIS, N.B.H., TINDLE, A.G. 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology; volume 25, pages 956–983. https://doi.org/10.1093/petrology/25.4.956.

 

 

Suggested Citation

Ministère de l’Énergie et des Ressources naturelles (MERN). Lépante Suite. Quebec Stratigraphic Lexicon. http://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-superieur/intrusion-de-lepante_en [accessed on Day Month Year].

 

Contributors

First publication

Anne-Marie Beauchamp, Eng., M.Sc. anne-marie.beauchamp@mern.gouv.qc.ca (redaction)

Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Patrice Roy, P. Geo., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Ricardo Escobar Moran (HTML editing); Céline Dupuis, P. Geo., Ph.D. (English version). 

 

 

 

1 février 2021