|Author(s):||Verpaelst et al., 2000|
|Type area:||Koroc River area (NTS sheet 24I)|
|Geological province:||Churchill Province|
|Geological subdivision:||Falcoz Lithotectonic Domain|
The term Baudan Complex was first used by Verpaelst et al. (2000) to define a unit of granitic gneiss and granitic intrusions. This unit name was not subsequently used by Simard et al. (2013), Lafrance et al. (2015, 2016) and Charette et al. (2016), who preferred to distinguish regional gneiss zones from late intrusions. The grey gneisses of tonalitic to granitic composition were then assigned to the Ungava Complex. However, in the synthesis of the southeastern part of the Churchill Province (Lafrance et al., 2018), different lithotectonic domains were identified and it appears that the gneisses observed within these different domains are distinct from each other. In the Falcoz Lithotectonic Domain, all grey tonalitic to granitic gneisses have been grouped into the Kangiqsualujjuaq Complex by Mathieu et al. (2018). This complex thus includes some of the outcrops previously assigned to the Baudan Complex by Verpaelst et al. (2000), and those of grey granitic gneisses, but excludes the later intrusive rocks which have been assigned to the Qarliik Suite (Mathieu et al., 2018), and the porphyroclastic monzogranite outcrops which now represent the Baudan Suite as defined by Mathieu et al. (2018). Porphyroclastic monzonite outcrops located in the eastern part of the Falcoz Lithotectonic Domain and previously assigned to the Inuluttaliq Suite have also been grouped into the Baudan Suite (Lafrance and Vanier, 2022).
The Baudan Suite comprises only one unit of porphyroclastic monzogranite (nAban1) associated with positive aeromagnetic anomalies.
Baudan Suite 1 (nAban1): Porphyroclastic Monzogranite
Unit nAban1 is predominantly composed of monzogranite but also has a small proportion of quartz monzonite, granodiorite and syenogranite. Monzogranite is strongly foliated (or lineated) and locally takes on the appearance of an augen gneiss or a protomylonite. The rock is medium to coarse grained, medium pink, and black and white speckled. The minerals form fine-grained recrystallized monomineralic clusters, particularly on the grain edges. The monzogranite is magnetic and characterized by the presence of 15 to 55% pink microcline porphyroclasts 0.5 to 3 cm long, commonly recrystallized and lenticular. Quartz tends to concentrate in thin discontinuous bands or lenses. It shows a strong undulatory extinction and its edges are commonly indented. Ferromagnesian minerals (10-25%) form lenticular clusters and anastomosed laminaes that mould quartzofeldspathic mineral clusters. Hornblende and biotite occur in similar proportions. The microcline is commonly perthitic, myrmekitic rimmed and contains aligned inclusions of plagioclase, quartz and biotite. The presence of recrystallization tails on either side of feldspar phenocrysts is also common. Accessory minerals are numerous and frequently coarse. The main minerals are allanite, epidote, magnetite, sphene, apatite, muscovite, zircon, garnet and chlorite.
Baudan Suite 1a (nAban1a): Porphyroclastic Farsundite
Locally, porphyroclastic monzogranite contains hypersthene and has been assigned to subunit nAban1a. Some outcrops include monzogranite (nAban1) and farsundite (nAban1a) in diffuse or transitional contact.
The structural and mineralogical characteristics of the farsundite are similar to those of unit nAban1 except the presence of hypersthene and lower proportions of biotite. Hypersthene is variable uralitized (hornblende rim) and serpentinized. The rock also takes on a green or brown sugar colour characteristic of orthopyroxene rocks.
Thickness and Distribution
The Baudan Suite covers an area of ~387 km2 and is concentrated in the northeast sector of the Falcoz Lithotectonic Domain (Lafrance and Vanier, 2022). It forms multi-kilometre klippes that extend between 5 and 40 km in a general NW-SE axis.
An age of ~2623 Ma was obtained in a sample described as a gneissic porphyritic monzogranite in the Koroc River area (Verpaelst et al., 2000). A second age of ~2673 Ma appears to confirm the Neoarchean emplacement of this unit. However, the inclusion of this outcrop in the Baudan Suite remains uncertain due to the strong deformation of the sample, which was collected within the Falcoz Shear Zone (flzSZ).
|Unit||Sample Number||Isotopic System||Mineral||Crystallization Age (Ma)||(+)||(-)||Reference(s)|
|nAban1||1998-SP-4049A||U-Pb||Zircon||2622.5||8.2||8.2||David et al., 2009|
The Baudan Suite is part of the ancient rocks of the Falcoz Lithotectonic Domain. The relationships with the other Archean rocks were not observed in the field. It is cut by granitic intrusions of the Qarliik Suite.
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Publications available through SIGÉOM Examine
CHARETTE, B., LAFRANCE, I., MATHIEU, G., 2016. Géologie de la région du lac Jeannin, Québec, Canada. MERN; BG 2015-01, 1 plan.
DAVID, J., MAURICE, C., SIMARD, M., 2009. DATATIONS ISOTOPIQUES EFFECTUEES DANS LE NORD-EST DE LA PROVINCE DU SUPERIEUR – TRAVAUX DE 1998, 1999 ET 2000. MRNF; DV 2008-05, 92 pages.
LAFRANCE, I., BANDYAYERA, D., BILODEAU, C., 2015. GEOLOGIE DE LA REGION DU LAC HENRIETTA (SNRC 24H). MERN; RG 2015-01, 62 pages, 1 plan.
LAFRANCE, I., BANDYAYERA, D., CHARETTE, B., BILODEAU, C., DAVID, J., 2016. GEOLOGIE DE LA REGION DU LAC BRISSON (SNRC 24A). MERN; RG 2015-05, 64 pages, 1 plan.
LAFRANCE, I., CHARETTE, B., VANIER, M.-A., 2018. Sud-est de la Province de Churchill, Nunavik, Québec, Canada: synthèse de la géologie. MERN; BG 2018-12.
LAFRANCE, I., CHARETTE, B., VANIER, M.-A., 2018. Southeastern Churchill Province, Nunavik, Québec, Canada: Geological Synthesis. MERN; BG 2018-12.
LAFRANCE, I., VANIER, M.-A., 2022. Domaine lithotectonique de Falcoz, sud-est de la Province de Churchill, Nunavik, Québec, Canada : synthèse de la géologie. MERN; BG 2022-01, 2 plans.
MATHIEU, G., LAFRANCE, I., VANIER, M.-A., 2018. Géologie de la région de pointe Le Droit, Province de Nain et sud-est de la Province de Churchill, Nunavik, Québec, Canada. MERN; BG 2018-07, 4 plans.
MATHIEU, G., LAFRANCE, I., VANIER, M.-A., 2018. Geology of the Pointe Le Droit region, Southeastern Churchill Province, Nunavik, Québec, Canada. MERN; BG 2018-07, 4 plans.
SIMARD, M., LAFRANCE, I., HAMMOUCHE, H., LEGOUIX, C., 2013. GEOLOGIE DE LA REGION DE KUUJJUAQ ET DE LA BAIE D’UNGAVA (SNRC 24J, 24K). MRN; RG 2013-04, 62 pages, 1 plan.
VERPAELST, P., BRISEBOIS, D., PERREAULT, S., SHARMA, K. N. M., DAVID, J., 2000. Géologie de la région de la rivière Koroc et d’une partie de la région de Hébron, 24I et 14L. MRN; RG 99-08, 62 pages, 10 plans.
Ministère de l’Énergie et des Ressources naturelles (MERN). Baudan Suite. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-de-churchill/suite-de-baudan_en [accessed on Day Month Year].
Isabelle Lafrance, P. Geo., M.Sc. email@example.com (redaction)
Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Julie Vallières, P. Geo., B.Sc. (critical review and editing); Céline Dupuis, P. Geo., Ph.D. (English version); Nathalie Bouchard and Ricardo Escobar Moran (HTML editing).
Isabelle Lafrance, P. Geo., M.Sc. (redaction)
Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Marc-Antoine Vanier, Eng., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Dominique Richard, GIT, Ph.D. (English version); André Tremblay (HTML editing).