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Lepers Suite
Stratigraphic label: [ppro]ler
Map symbol: pPler

First published: 19 April 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
None
 
Author:Mathieu et al., 2018
Age:Paleoproterozoic
Reference section: 
Type area:Point Le Droit area (NTS sheet 24P)
Geological province:Nain Province
Geological subdivision:Burwell Lithotectonic Domain
Lithology:Olivine websterite
Type:Lithodemic
Rank:Suite
Status:Formal
Use:Acive

 

 

Background

Van Kranendonk et al. (1994) and Van Kranendonk and Wardle (1994) mapped ultramafic lithologies that they associate with the Tasiuyak Gneiss and Noodleook Complex in the Lorière Lake (NTS sheet 24P10) and Ryans Bay (sheet 24P09) area. Mathieu et al. (2018) corroborate these observations in the Point Le Droit area (sheet 24P) and Grenfeld Sound area (sheet 25A). They also map websterites in rocks of the Killinek Suite and introduce the Lepers Suite to group ultramafic intrusions of the Burwell Domain spatially associated with both metasedimentary rocks and gneiss and intrusions.

 

Description

The Lepers Suite consists solely of a metamorphosed ultramafic intrusive rock unit (pPler). Samples show high magnetic susceptibility but the small size of intrusions, combined with a very wide mesh aeromagnetic survey, makes it impossible to separate this unit based on the geophysical survey (Geological Survey of Canada, 1985). However, rocks are easily visible in the field due to the whaleback appearance of outcrops, their dark brown patina and elephant skin texture. Some magmatic textures, such as cumulate horizons, are generally preserved despite deformation and metamorphism. Outcrops are homogeneous and only composed of olivine websterite and show magmatic bedding. Serpentine veins and magnetite ridges are frequently observed. Bands of olivine-relic cumulate are reported. The patina is dark brown and the rock is very dark green in fresh exposure.

Preserved primary phases are surrounded by a finer, even-grained matrix composed mostly of actinolite, clinopyroxene and orthopyroxene. Rocks are composed of actinolite (25-30%), orthopyroxene partially replaced by iddingsite and carbonates (20-50%), partially serpentinized olivine (5-30%), clinopyroxene (5-20%), magnetite (5-10%) and green (herspinitis) and locally brown (picotite) spinel. Orthopyroxene and clinopyroxene are medium to coarse grained with a finer granoblastic rim. They incorporate oxides in slats into the cleavage of the preserved core. Orthopyroxene and olivine are altered to iddingsite and serpentine, respectively, matted or in veins. Olivine is cracked and also forms coarse-grained zones. Opaque minerals are disseminated homogeneously. Foliation is marked by a slight preferential orientation of stocky actinolite.

 

Thickness and Distribution

Intrusive and metamorphosed rocks of the Lepers Suite are observed east and north of the Abloviak Shear Zone. They form oblong masses of reduced size, 10 to 200 m long for a few metres to a few decametres wide.

 

Dating

None.

Stratigraphic Relationship(s)

Rocks of the Lepers Suite are observed in contact with migmatitic paragneiss of the Tasiuyak Complex and also with orthopyroxene quartz diorite of the Killinek Suite. 

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
COMMISSION GÉOLOGIQUE DU CANADA (CGC)Magnetic anomaly map, Torngat Mountains, Newfoundland and Quebec / Carte des anomalies magnétiques, Torngat Mountains, Terre – Neuve et Québec, Commission géologique du Canada. Série nationale des sciences de la Terre. Cartes des anomalies magnétiques NO-20-M; 1 plan.1985Source
MATHIEU, G. – LAFRANCE, I. – VANIER, M.-A.Géologie de la région de pointe le Droit, sud-est de la Province de Churchill, Nunavik, Québec, Canada. Ministère de l’énergie et des ressources naturelles, Québec.2018Bulletin géologiQUE
VAN KRANENDONK, M.J. – WARDLE, R.J. Geology, Ryans Bay, Newfoundland (Labrador)-Quebec. Commission géologique du Canada; dossier public 2926, 1 carte.1994Source
VAN KRANENDONK, M.J. – WARDLE, R.J. –  MENGEL, F.C. – CHURCHILL, R. –  CAMPBELL, L.M. –  SCHWARTZ, S. Geology, Lac de Lorière, Newfoundland (Labrador)-Quebec. Commission géologique du Canada; dossier public 2925, 1 carte.1994Source

 

12 novembre 2018