First published: 20 January 2020
Last modified:
DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
| Author(s): | Dimroth, 1968 |
| Age: | Paleoproterozoic |
| Stratotype: | The type locality is to the east of Du Chambon Lake (NTS sheet 24B05). |
| Type area: | Du Chambon Lake area (NTS sheet 24B05) |
| Geological province: | Churchill Province |
| Geological subdivision: | New Quebec Orogen (Labrador Trough) |
| Lithology: | Slate, siltstone, greywacke, dolomite |
| Category: | Lithostratigraphic |
| Rank: | Formation |
| Status: | Formal |
| Use: | Active |
Background
The name Du Chambon Formation was introduced by Dimroth (1968) to designate a unit of black slate with lesser amounts of greywacke, which is located east of Du Chambon Lake. The majority of the rocks in this unit have been mapped by Dimroth (1970, 1972, 1978) and Clark (1986). They have also been studied by Kish and Tremblay-Clark (1978), Kearvell (1985), Kearvell and Clark (1988) and Kish (1994) to assess their mineral potential.
Description
The Du Chambon Formation represents an allochthonous package of sedimentary rocks. It consists mainly of black or grey, commonly graphitic and finely bedded slate and siltstone. The unit also includes fine-grained black graphitic greywacke, which is more abundant than slate in places, notably in the Duvic Cove area in the NW part of Romanet Lake (sheet 24B05). A few beds of grey dolomite having a brown patina or of fine-grained quartz-graphite wacke are observed locally (Dimroth, 1978). The Du Chambon slate is enriched in graphite and locally has a rusty patina due to the presence of sulphides (Clark, 1986; Kish, 1994). A slightly dolomitic grey quartzite having a light rusty brown alteration patina and nodular structure forms the upper part of the formation (Dimroth, 1978). This rock, also described as sandstone-pebble conglomerate (Dimroth, 1978), has been reinterpreted by Kearvell and Clark (1988) as intrusive polymictic breccia. It is thought to belong to the Mistamisk Volcanic Complex. According to Dimroth (1978), the various sandstones of the Swampy Bay Group, which includes the Du Chambon Formation, are probably turbidites whose components are derived from a sedimentary source area.
Du Chambon Formation 1 (pPdc1): Black Graphitic Slate, Dark Grey Siltstone and Graphitic Greywacke; Interbedded with Dolomite or Quartz-Graphite Wacke
This unit consists of dark grey to black, commonly graphitic and finely bedded slate and siltstone, with lesser amounts of fine-grained, black graphitic greywacke. Grey dolomite having a brown alteration patina is locally interbedded, up to 30 cm thick, with slate in the area north of Du Chambon Lake. Dimroth (1978) points out that dolomite beds are absent between Du Chambon Lake and Romanet Lake, but that some fine-grained quartz-graphite wacke beds are found there. Slate is well folded and has an undulatory slaty cleavage due to a crenulation cleavage that cuts it (Clark, 1986). In places, the slate’s surface is rusty due to the presence of disseminated pyrite or millimetric veinlets along the slaty cleavage. Rare traces of chalcopyrite are noted by Clark (1986) in pyrite veinlets. Quartz veins 2 to 15 cm thick cut slate in places (Clark, 1986). Kish (1994) determined that the organic material in the formation is composed of relict kerogen grains surrounded by spongy, amorphous graphite.
Du Chambon Formation 2 (pPdc2): Black Graphitic Slate, Black Graphitic Greywacke and Minor Amount of Dark Grey Siltstone
This unit is located in the Duvic Cove area, in the NW part of Romanet Lake (sheet 24B05). It consists of 30 to 180 cm thick beds of very fine-grained black graphitic greywacke and minor amounts of dark grey siltstone, with interbedded black graphitic slate (10-60 cm) (Dimroth, 1978).
Thickness and distribution
The Du Chambon Formation belongs to the Wheeler Lithotectonic Zone as defined by Clark and Wares (2004). It extends over a length of ~22 km and a maximum width of 2.5 km between the NW end of Du Chambon Lake (sheet 24C08) and Duvic Cove, in the NW part of Romanet Lake (sheet 24B05).
Dating
The deposition of rocks belonging to the Du Chambon Formation occurred between 2169 ±4 Ma and 2142 +4/-2 Ma, i.e. during the period of deposition of first cycle sediments (T. Krogh and B. Dressler, unpublished data cited by Clark, 1984, page 4; Rohon et al., 1993; Clark and Wares, 2004).
Stratigraphic Relationship(s)
The Du Chambon Formation unconformably overlies dolomite of the Uvé Formation (Pistolet Group). However, its summit is not exposed (Dimroth, 1978). The contact between the Du Chambon and Uvé formations is well exposed at the type locality and NE of the Duvic Cove (Dimroth, 1978). It is characterized by interstratified slate, dolomite and chert at 10 cm to 1 m scale (Clark, 1986). Dimroth (1978) raised the possibility of a correlation between the Du Chambon and Romanet formations further east, and that the Du Chambon Formation gradually changes to the Romanet Formation. Deposition of Du Chambon sediments and thick flyschoid sequences of the Swampy Bay Group are thought to be due to uplift of source areas. According to Dimroth (1978), these source areas were probably sedimentary in nature because there is an absence of volcanic and metamorphic components in Swampy Bay sandstone. The polymictic intrusive breccia piles (Mistamisk Complex) were emplaced in the Lace Lake, Uvé, Du Chambon, Romanet and Bacchus formations between Du Chambon Lake and the Romanet River (sheets 24B05 and 24C08) (Kearvell, 1985; Clark, 1986; Kearvell and Clark, 1988). A thrust fault (Du Chambon Fault), mapped by Dimroth (1978), places the Du Chambon Formation adjacent to the Chakonipau and Dunphy formations (Seward Group) between Du Chambon and Romanet lakes.
Paleontology
Does not apply.
References
Publications Available Through SIGÉOM Examine
CLARK, T. 1984. GÉOLOGIE DE LA RÉGION DU LAC CAMBRIEN – TERRITOIRE DU NOUVEAU-QUÉBEC; MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES; QUÉBEC; ET 83-02, 77 pages and 1 plan.
CLARK, T. 1986. GÉOLOGIE ET MINÉRALISATIONS DE LA RÉGION DU LAC MISTAMISK ET DE LA RIVIÈRE ROMANET; MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES; QUÉBEC; ET 83-22, 56 pages and 1 plan.
CLARK, T., WARES, R. 2004. SYNTHÈSE LITHOTECTONIQUE ET MÉTALLOGÉNIQUE DE L’OROGÈNE DU NOUVEAU-QUÉBEC (FOSSE DU LABRADOR); MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES; QUÉBEC; MM 2004-01, 182 pages and 1 plan.
DIMROTH, E. 1984. CARTES GÉOLOGIQUES DU LAC ROMANET ET DU LAC CRAMOLET (FOSSE DU LABRADOR). MINISTÈRE DES RICHESSES NATURELLES, QUÉBEC; DP 068, 3 plans.
DIMROTH, E. 1972. STRATIGRAPHY OF PART OF THE CENTRAL LABRADOR TROUGH. MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES, QUÉBEC; DP 154, 304 pages and 6 plans.
DIMROTH, E. 1978. RÉGION DE LA FOSSE DU LABRADOR ENTRE LES LATITUDES 54°30′ ET 56°30′. MINISTÈRE DE RICHESSES NATURELLES, QUÉBEC; RG 193, 417 pages and 16 plans.
KEARVELL, G. 1985. BRÈCHES ET ALTÉRATIONS ALBITIQUES DE LA RIVIÈRE ROMANET. MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES, QUÉBEC; DP-85-24, 2 plans.
KEARVELL, G., CLARK, T. 1988. ÉTUDE D’INDICES AU-U ET DE BRÈCHES POLYGÉNIQUES DANS LA VALLÉE DES LACS MISTAMISK ET ROMANET – FOSSE DU LABRADOR. MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES, QUÉBEC; DP-87-24, 32 pages and 1 plans.
KISH, L. 1994. SHALES NOIRS DANS LA FOSSE DU LABRADOR, QUÉBEC. MINISTÈRE DES RESSOURCES NATURELLES, QUÉBEC; MB 94-43, 16 pages.
KISH, L., TREMBLAY-CLARK, P. 1978. GÉOCHIMIE ET RADIOACTIVITÉ DANS LA FOSSE DU LABRADOR, 56°00′ – 58°30′. MINISTÈRE DES RICHESSES NATURELLES, QUÉBEC; DPV-567, 73 pages.
Other Publications
DIMROTH, E. 1968. Sedimentary textures, diagenesis, and sedimentary environment of certain Precambrian ironstones. Neues Jahrbuch Fuer Geologie Und Palitontologie, Abhandlungen, 1968. volume 130, pages 247-274.
ROHON, M.-L., VIALETTE, Y., CLARK, T., ROGER, G., OHNENSTETTER, D., VIDAL, P. 1993. Aphebian mafic-ultramafic magmatism in the Labrador Trough (New Quebec): its age and the nature of its mantle source. Canadian Journal of Earth Sciences; volume 30, pages 1582-1593. http://doi.org/10.1139/e93-136
Suggested Citation
Ministère de l’Énergie et des Ressources naturelles (MERN). Du Chambon Formation. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-de-churchill/formation-de-du-chambon_en [accessed on Day Month Year].
Contributors
First publication | Charles St-Hilaire, GIT, M.Sc. charles.st-hilaire@mern.gouv.qc.ca (redaction) Mehdi A. Guemache, P. Geo., Ph.D. (redaction and coordination); Thomas Clark, P. Geo., Ph.D. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Céline Dupuis, P. Geo., Ph.D. (English version); Ricardo Escobar Moran (HTML editing). |