DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
|Author(s):||Frarey and Duffell, 1964|
|Stratotype:||Around the town of Schefferville (NTS sheet 23J15, UTM NAD83, zone 19: 639276 m E, 6074688 m N)|
|Type area:||Schefferville area|
|Geological province:||Churchill Province|
|Geological subdivision:||New Quebec Orogen (Labrador Trough)|
|Lithology:||Iron formation, mudrock, siltite, sandstone, quartzitic arenite, pelitic schist and volcanic rocks|
Geologists of the Labrador Mining and Exploration Company used the term « Ferriman Series » in 1949 to refer to a sequence of quartzites and iron-bearing rocks located between argillaceous units of the Attikamagen Group and Menihek Formation. This sequence was part of a larger, predominantly sedimentary sequence, which they divided into three units called « Hamilton River », « Ferriman » and « Point » (Frarey and Duffel, 1964). Following his work near Schefferville, Harrison (1952) was unable to corroborate the usefulness of these terms and proposed the name « Knob Lake Group » to designate the entire sequence containing iron-bearing rocks of the Trough. According to Harrison (1952), the « Knob Lake Group » consisted of the following formations, from bottom to top: Attikamagen, Denault, Fleming, Wishart, Ruth, Sokoman and Menihek. Following their work, Frarey and Duffell (1964) added the Seward and Purdy formations and the list of formations became, from bottom to top: Seward, Attikamagen, Denault, Fleming, Wishart, Ruth, Sokoman, Purdy and Menihek. Dimroth (1969, 1970, 1978) further divided the « Knob Lake Group » into subgroups named, from bottom to top: Seward, Pistolet, Swampy Bay and Ferriman. The « Ferriman Subgroup » then included, from bottom to top, the Wishart, Ruth and Sokoman formations.
Clark and Wares (2004) reclassified all Dimroth Subgroups as groups and suggested that the name « Knob Lake Group » be abandoned as superfluous. Furthermore, this abandonment resulted from the interpretation that part of this group, the part containing iron-bearing rocks, is the chronostratigraphic equivalent of part of the Doublet Group (Le Gallais and Lavoie, 1982). For Clark and Wares (2004), it was more consistent to give another name to the restricted sequence containing iron-bearing rocks, hence the name « Ferriman Group ». The Ferriman Group comprises, from base to top, the Wishart, Ruth, Sokoman and Menihek formations (Clark and Wares, 2004).
Several formation names exist for units that are equivalent to parts of the Ferriman Group. Clark and Wares (2004) proposed to abandon the following formation names: « Alison Formation » (equivalent to the Wishart; Bérard, 1965), « Fenimore Formation » (equivalent to the Sokoman; Berard, 1965), « Larch River Formation » (equivalent to the Menihek; Bergeron, 1954), « Dragon Formation » (equivalent to part of the Menihek; Berard, 1965), and « Nachicapau Formation » (equivalent to parts of the Ferriman Group; Dressler, 1979).
The Ferriman Group was defined by Clark and Wares (2004) as the autochthonous/parautochthonous sequence of the second volcano-sedimentary cycle on the western margin of the Labrador Trough. It consists of a sequence of platform sediments and turbidites that reflect a marine transgression. Variations in sedimentary facies from west to east reflect changes in depositional environments (Wardle and Bailey, 1981). The Ferriman Group includes, from base to top: quartzitic sandstones and arenites of the Wishart Formation; mudstones, siltstones, iron-bearing sandstones and cherts of the Ruth Formation; iron-bearing and cherty sedimentary rocks of the Sokoman Formation; and sandstones, mudstones and turbidites of the Menihek Formation (Clark and Wares, 2004; Dimroth, 1978). It should be noted that the summit part of the Menihek Formation, in the central and northern part of the Trough, locally contains volcanic rocks likely correlative with the base of the Hellancourt Formation (Dimroth, 1978; Clark and Wares, 2004).
The degree of metamorphism of Ferriman Group rocks is low and increases from west to east, from the greenschist facies to the upper greenschist facies (Baragar, 1967; Dimroth and Dressler, 1978). In the northern end of the Trough, metamorphism reaches the amphibolite facies (Dimroth and Dressler, 1978; Fraser et al., 1978). The Ferriman Group (from the Wishart to the Menihek Formation) is the result of the collapse and progressive flooding of a platform (Wardle and Bailey, 1981). Dimroth (1978) emphasizes the importance of the Ferriman Group from an economic point of view for its vast iron resources, but also because it offers regional correlation.
Thickness and Distribution
The Ferriman Group extends the full 850 km length of the Labrador Trough, mainly along its western margin. It has been recognized in the Bérard, Cambrien, Mélèzes, Payne, Schefferville and Tamarack lithotectonic zones, as defined by Clark and Wares (2004). Its true thickness is variable and difficult to estimate as it is affected by faults and folding associated with Hudsonian deformation. The Ferriman Group is absent west of Castignon Lake (sheet 24C07), with the exception of the Goethite Lake area, and between Ritchie and Purdy lakes (sheet 23O12). This absence west of Castignon Lake is not related to a depositional gap, but rather to erosion of the Ferriman Group exposing the underlying sequence. The formations that make up the Ferriman Group can be traced from the northern end of the orogen to the Grenville Front southward. The group is also recognized within the Grenville Province (Dimroth, 1978), where the equivalent sequence forms the Gagnon Group (Dimroth et al., 1970; Rivers, 1980).
The second cycle of sedimentation in the Labrador Trough is dated 1.88 Ga to 1.87 Ga and begins with the deposition of the Ferriman Group (Clark and Wares, 2004). U-Pb analysis of a large zircon crystal from a carbonatite dyke of the Castignon Volcanic Complex, contemporaneous with the Sokoman Formation, dates the onset of Ferriman deposition before 1880 ±2 Ma (Chevé and Machado, 1988). This age is also a minimum age for the onset of the Menihek Formation, since Dressler (1979) mentions that no Castignon Complex intrusions cut the latter. Weak volcanic activity was contemporaneous with the deposition of the Sokoman Formation at the beginning of the second cycle. It was dated 1878 ±1 Ma by the U-Pb method on zircons in a quartz syenite pebble from a conglomerate layer intercalated in Nimish volcanics (Findlay et al., 1995). This indicates that, in the southern part of the Trough, the onset of Sokoman deposition predates 1878 Ma. Volcanic activity peaked towards the end of the second cycle, dated 1874 ±3 Ma by the U-Pb method on zircons from a glomerophyric gabbro sill cutting basalts at the top of the Hellancourt Formation in the northern part of the orogen (Machado et al., 1997). SW of Le Moyne Lake, an age of 1870 ±4 Ma was obtained by Machado et al. (1997) for rhyodacite, which represents the youngest age for rocks of the second cycle. The Ferriman Group is thought to be the same age as the Baby-Hellancourt sequence of the Koksoak Group (Clark, 1988; Clark and Wares, 2004).
The Ferriman Group overlies, in erosional unconformity, Archean rocks of the Superior Province and rocks of the first volcano-sedimentary cycle along the western margin of the orogen. Further east, the Ferriman Group overlies rocks of the Attikamagen Group in low-angle erosional unconformity or with progressive and conformable contacts (Dimroth, 1971, 1978). According to Dimroth (1971), the best exposure of the Attikamagen-Ferriman contact is between latitudes 55°30’N and 54°30’N. In the southern part of the orogen, the Doublet Group structurally overlies the top of the Ferriman Group (Menihek Formation) along the Lac Walsh Fault (Wardle and Bailey, 1981; Findlay et al., 1995). At the northern end of the Trough, the Ferriman Group is in fault contact with Archean bedrock (Madore and Larbi, 2000). In addition, it is overlain by the Hellancourt Formation (Koksoak Group) and locally by the Attikamagen Group (Clark and Wares, 2004). In the south-central and northern parts of the Labrador Trough, the Ferriman Group can be chronostratigraphically correlated with the Doublet, Koksoak and Le Moyne volcano-sedimentary groups deposited in a basin further east (Frarey, 1967; Clark, 1988; Findlay et al., 1995; Clark and Wares, 2004). North of the Trough, it is unconformably overlain by the Chioak Formation (Bérard, 1965; Clark, 1979, 1988; Clark and Wares, 2004). On the Labrador side, the Ferriman Group is unconformably overlain by the Tamarack River Formation (Ware, 1979; Ware, 1980; Wardle and Bailey, 1981; Clark and Wares, 2004).
In the Hematite Lake area (sheet 24C), alkaline to hyperalkaline intrusive and effusive rocks (meimechites, carbonatites) of the Castignon Volcanic Complex (Chevé, 1993; Dressler, 1979) are interstratified with the Sokoman Formation. In the southern part of the Trough, subaerial volcanic rocks of alkaline composition, known as « Nimish » (Zajac, 1974; Evans, 1978; Wardle and Bailey, 1981), are intercalated within the Wishart and Sokoman formations. Numerous gabbroic sills belonging to the Gerido Intrusive Suite (formerly Montagnais Sills) cut the upper part of the Ferriman Group (Menihek Formation) in the south-central part of the Trough (Dimroth, 1978; Wardle and Bailey, 1981; Findlay et al., 1995).
Dressler (1979) reports the presence of nested cone structures in the Menihek Formation east of Chocolate Lake (sheet 24C10). The photo presented in this report (Figure 32) suggests traces of a living organism.
Publications Available Through SIGÉOM Examine
BERARD, J., 1965. REGION DU LAC BERARD, NOUVEAU-QUEBEC. MRN; RG 111, 175 pages, 2 plans.
CHEVE, S., 1993. CADRE GEOLOGIQUE DU COMPLEXE CARBONATIQUE DU LAC CASTIGNON – FOSSE DU LABRADOR. MRN; MB 93-64, 100 pages, 1 plan.
CLARK, T., 1979. REGION DU LAC NAPIER (NOUVEAU-QUEBEC) – RAPPORT PRELIMINAIRE. MRN; DPV 663, 28 pages, 1 plan.
CLARK, T., 1987. STRATIGRAPHIE, PETROGRAPHIE ET PETROCHIMIE DE LA FORMATION DE FER DE BABY DANS LA REGION DU LAC HERODIER (FOSSE DU LABRADOR). MRN; ET 87-13, 44 pages.
CLARK, T., WARES, R., 2004. SYNTHESE LITHOTECTONIQUE ET METALLOGENIQUE DE L’OROGENE DU NOUVEAU-QUEBEC (FOSSE DU LABRADOR). MRNFP; MM 2004-01, 182 pages, 1 plan.
DIMROTH, E., 1969. GEOLOGIE DE LA REGION DU LAC CASTIGNON, TERRITOIRE DU NOUVEAU-QUEBEC. MRN; RP 571, 62 pages, 7 plans.
DIMROTH, E., 1978. Région de la fosse du Labrador entre les latitudes 54° 30′ et 56° 30′. MRN; RG 193, 417 pages, 16 plans.
DRESSLER, B., 1979. Région de la fosse du Labrador. MRN; RG 195, 136 pages, 14 plans.
MADORE, L., LARBI, Y., 2000. GEOLOGIE DE LA REGION DE LA RIVIERE ARNAUD (SNRC 25D) ET DES REGIONS LITTORALES ADJACENTES (SNRC 25C, 25E, 25F). MRN; RG 2000-05, 39 pages, 4 plans.
BARAGAR, W.R.A., 1967. Wakuach Lake map-area, Quebec-Labarador (23O). Geological Survey of Canada; Memoir 344, 174 pages. https://doi.org/10.4095/123960
BERGERON, R., 1954. A study of the Quebec-Labrador iron belt between Derry Lake and Larch River. Doctoral thesis, Université Laval, Québec, D.Sc. thesis, vol. 230.
CHEVÉ, S.R., MACHADO, N., 1988. Reinvestigation of the Castignon Lake carbonatite complex, Labrador Trough, New Québec. Joint Annual Meeting of the Geological Association of Canada and the Mineralogical Association of Canada, St. John’s, Newfoundland; Program with Abstracts, volume 13, pages 20.
DIMROTH, E., 1970. Evolution of the Labrador Geosyncline. Geological Society of America Bulletin; volume 81, pages 2717-2742. https://doi.org/10.1130/0016-7606(1970)81[2717:EOTLG]2.0.CO;2
DIMROTH, E., 1971. The Attikamagen-Ferriman transition in part of the central Labrador Trough. Canadian Journal of Earth Sciences; volume 8, pages 1432-1454 .https://doi.org/10.1139/e71-132
DIMROTH, E., DRESSLER, B., 1978. Metamorphism of the Labrador Trough. In: Metamorphism in the Canadian Shield. Geological Survey of Canada; Study 78-10, pages 215-236. https://doi.org/10.4095/104534
DRESSLER, B., 1975. Lamprophyres of the north-central Labrador Trough, Quebec, Canada. Neues Jahrbuch für Mineralogie, Monatshefte; volume 6, pages 268-280.
EVANS, J.L., 1978. The geology and geochemistry of the Dyke Lake area (parts of 23J8, 9), Labrador. Newfoundland Department of Mines and Energy, Mineral Development Division; Report 78-4, 39 pages. https://gis.geosurv.gov.nl.ca/geofilePDFS/WBox040/023J_0058.pdf
FINDLAY, J.M., PARRISH, R.R., BIRKETT, T., WATANABE D.H., 1995. U-Pb ages from the Nimish Formation and Montagnais glomeroporphyritic gabbro of the central New Québec Orogen, Canada. Canadian Journal of Earth Sciences; volume 32, pages 1208-1220. https://doi.org/10.1139/e95-099
FRAREY, M.J. 1967. Willbob Lake and Thompson Lake map-areas, Quebec and Newfoundland (23 O/1 and 23 O/8). Geological Survey of Canada; Memoir 348, 73 pages. https://doi.org/10.4095/123896
FRAREY, M.J., DUFFEL, S., 1964. Revised stratigraphic nomenclature for the central part of the Labrador Trough. Geological Survey of Canada; Paper 64-25, 13 pages. https://doi.org/10.4095/123909
FRASER, J.A., HEYWOOD, W.W., MAZURSKI, M.A., 1978. Carte métamorphique du Bouclier Canadien. Geological Survey of Canada; Map 1475A. https://doi.org/10.4095/133909
FRYER, B.J., 1972. Age determinations in the Circum-Ungava Geosyncline and the evolution of Precambrian banded iron formations. Canadian Journal of Earth Sciences; volume 9, pages 652-663. https://doi.org/10.1139/e72-055
HARRISON, J.M., 1952. The Quebec-Labrador iron belt, Quebec and Newfoundland. Geological Survey of Canada; Paper 5220, 21 pages. https://doi.org/10.4095/123923
LE GALLAIS, C.J., LAVOIE, S., 1982. Basin evolution of the Lower Proterozoic Kaniapiskau Supergroup, central Labrador Miogeocline (Trough), Quebec. Bulletin of Canadian Petroleum Geology; volume 30, pages 150-166. https://doi.org/10.35767/gscpgbull.30.2.150
MACHADO, N., CLARK, T., DAVID, J., GOULET, N., 1997. U-Pb ages for magmatism and deformation in the New Quebec Orogen. Canadian Journal of Earth Sciences; volume 34, pages 716-723. https://doi.org/10.1139/e17-058
WARDLE, R.J., BAILEY, D.G., 1981. Early Proterozoic sequences in Labrador. In: Proterozoic Basins in Canada (F.H.A. Campbell, editor). Geological Survey of Canada; Study 81-10, pages 331-358. https://doi.org/10.4095/124192
WARE, M.J., 1980. Tamarack River Formation–Menihek Lake area, western Labrador. In: Current research (C. F. O’Driscoll and R. V. Gibbons, editors). Government of Newfoundland and Labrador, Department of Mines and Energy, Mineral Development Division; Report 80-01, pages 194-200. https://www.gov.nl.ca/iet/files/mines-geoscience-publications-currentresearch-1980-ware-cr1980.pdf
WARE, M.J., 1979. Geology of the Sims-Evening Lake area, western Labrador with emphasis on the Helikian Sims Group. Government of Newfoundland and Labrador, Department of Mines and Energy, Mineral Development Division; Report 79-01, 7 pages. https://www.gov.nl.ca/iet/files/mines-geoscience-publications-reportactivities-1979-ware-roa1979.pdf
ZAJAC, I.S., 1974. The stratigraphy and mineralogy of the Sokoman Formation in the Knob Lake area, Quebec and Newfoundland. Geological Survey of Canada; Bulletin 220, 159 pages. https://doi.org/10.4095/123946
Ministère de l’Énergie et des Ressources naturelles (MERN). Ferriman Group. Lexique stratigraphique du Québec. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-de-churchill/groupe-de-ferriman_en [accessed on Day Month Year].
Charles St-Hilaire, GIT, M.Sc. email@example.com; Thomas Clark, P. Geo., Ph.D. (redaction)
Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Simon Auclair, P. Geo., M.Sc. (critical review & editing); Céline Dupuis, P. Geo., Ph.D. (English version); Marie-Ève Lagacé and André Tremblay (HTML editing).