Français
 
Matachewan Dyke Swarm
Stratigraphic label: [ppro]maw
Map symbol: pPmaw

First published: 31 May 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
None
 
Author:Fahrig et al., 1965
Age:Paleoproterozoic
Reference section: 
Type area:District of Matachewan, Ontario (NTS sheet 041P15)
Geological province:Superior Province
Geological subdivision:Abitibi, Nemiscau, Opatica, La Grande, Pontiac, Wawa, Quetico and Wabigoon subprovinces
Lithology:Diabase
Type:Lithodemic
Rank:Lithodeme
Status:Formal
Use:Active

 

 

Background

The Canadian Shield diabase dyke swarms have been the subject of several works. The Matachewan Dyke Swarm is a family of diabase dykes that cuts the Canadian Shield north-south, first identified in the Matachewan area (NTS sheet 041P15). This dyke swarm was the subject of paleomagnetic (Fahrig et al., 1965), geochemical (Condie et al., 1987; Buchan et al., 2007) and geochronological (Fahrig and Wanless, 1963; Gates and Hurley, 1973; Heaman, 1997) studies.

Description

Dykes are characterized by a positive relief and a positive linear aeromagnetic anomaly. They are clearly visible on aeromagnetic maps because of their high magnetic susceptibility. They are not deformed and cut structural grain at high angles. The thickness of these dykes ranges from a few metres to a few tens of metres. The rock is brownish or orange-beige in altered surface and dark green to bluish grey in fresh exposure, massive and highly magnetic. The narrow dykes, along with contact margins of the thickest dykes, look like fast cooling zones and show thin plagioclase needles in an aphanitic matrix. There is an increase in grain size from the border to the centre of the dykes. The central part of the dykes, which is gabbroic to gabbronoritic, is medium to coarse grained to porphyritic. One of the main characteristics of the Matachewan Dyke Swarm is the porphyritic texture (plagioclase phenocrystals). Ophitic or subophitic texture is also often observed. The rock is composed of euhedral plagioclase laths whose interstitial spaces are filled by slightly chloritized pyroxene, as well as by an assemblage of magnetite, pyrite, chlorite, apatite and rare flakes of biotite.

The Matachewan Dyke Swarm is difficult to distinguish from the Lac Esprit Dykes because both have a north-south orientation. Buchan et al. (2007) were able to differentiate them through paleo-magnetic, geochemical and geochronological data. 

Thickness and distribution

The map of Buchan and Ernst (2004) shows the distribution of all diabase dyke swarms in Canada. The Matachewan Dyke Swarm is located in the south and centre of the Superior Province (Quebec and Ontario). Specifically, they are found in the Abitibi, Opatica, Nemiscau, La Grande, Pontiac, Wawa, Quetico and Wabigoon subprovinces. Some of these dykes can be followed over 500 km. In the Rodayer Lake area (sheets 32K13, 32K14, 32N03 and 32N04), these dykes can be up to 60 m thick (Bandyayera and Daoudene, 2017). 

Dating

Heaman (1997) conducted a geochronological study of baddeleyites and zircons collected from two Matachewan dyke samples and obtained ages of 2473 +16/-9 Ma and 2446 ±3 Ma. Fahrig and Wanless (1963) obtained an age of 2485 Ma from a total rock K-Ar analysis of a chilled margin sample of a Matachewan dyke. A Rb-Sr age of 2690 ±93 Ma was also obtained by Gates and Hurley (1973).

Isotopic SystemMineralCrystallization Age (Ma)(+)(-)Reference(s)
U-PbBaddeleyite2473169Heaman, 1997
U-PbBaddeleyite and zircon244633Heaman, 1997

Stratigraphic Relationship(s)

The Matachewan Dyke Swarm cuts the southern and central Archean rocks of the Superior Province.

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
HEAMAN, L.M.Global mafic magmatism at 2.45 Ga: Remnants of an ancient large igneous province? Geology; volume 25, pages 299-302.
 
1997Source
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, 2 cartes.2017RG 2017-01
FAHRIG, W.F. – WANLESS, R.K.Age and significance of diabase dyke swarms of the Canadian Shield. Nature, Volume 200, Issue 4910, pages 934-937.1963
FAHRIG, W.F. – GAUCHER, E.H. – LAROCHELLE, A.Paleomagnetism of diabase dykes of the Canadian Shield. Canadian Journal of Earth Sciences; volume 2, pages 278-298.1965Source
BUCHAN, K.L. – ERNST, R.E.Diabase dyke swarms and related units in Canada and adjacent regions. Commission géologique du Canada, Carte série « A » 2022A, 39 pages, 1 feuille.2004Source
GATES, T.M. – HURLEY, P.M.Evaluation of RbSr Dating Methods Applied to the Matachewan, Abitibi, Mackenzie, and Sudbury Dike Swarms in Canada. Canadian Journal of Earth Sciences; volume 10, pages 900-919.1973Source
CONDIE, K.C – BOBROW, D.J. – CARD, K.D.Geochemistry of Precambrian mafic dykes from the southern Superior Province of the Canadian Shield. Geological Association of Canada, Special Paper, volume 34, pages 95-108.1987
BUCHAN, K.L. – GOUTIER, J. – HAMILTON, A. – ERNST, R. E. – MATTHEWS, W. A.Paleomagnetism, U–Pb geochronology, and geochemistry of Lac Esprit and other dyke swarms, James Bay area, Quebec, and implications for Paleoproterozoic deformation of the Superior Province. Canadian Journal of Earth Sciences; volume 44, pages 643-664.2007Source

 

 

17 octobre 2018