Abstract
The Lac St-Jean anorthosite massif underlies an area of over 20,000 km2 and has been emplaced into migmatitic gneisses of the central granulite terrain of the Grenville Province of the Canadian shield. Field data and petrography in an area straddling the anorthosite-gneiss contact, close to Chicoutimi (Quebec) permits an outline of its tecto-magmatic evolution. Depositional magmatic textures in the massif reveals that it crystallized from a magma in a relatively calm tectonic environment. The absence of fusion in pelitic gneisses at the contact proves that the crystallization did not take place at the level presently exposed. The parallelism of subvertical foliation in the enveloping gneisses and the anorthosite indicates that both were deformed together. It is suggested that the deformation results from a diapiric ascent of the anorthosite massif after its consolidation at depth. The depth of consolidation of the anorthosite is estimated at ∼ 25–30 km from subsolidus reaction between plagioclase and olivine. The diapiric ascent is further substantiated by the fact that three sets of mafic dykes of different ages, intrusive into the anorthosite, have a mineralogy which indicates successively decreasing P, T conditions of emplacement from granulite fades to amphibolite facies. An evolution of the basement gneisses and the anorthosite is proposed as a working hypothesis; it relies on the fact that metabasite dyke swarms in the basement gneisses represent a period of major crustal extension and could be used as a stratigraphic subdivision of the Grenville Province.
Similar content being viewed by others
References
Baer AJ (1976) The Grenville Province in Helikian times: a possible model of evolution. Philos Trans R Soc London, A 280:499–515
Baer AJ, Emslie RF, Irving E, Tanner JG (1974) Grenville Geology and plate tectonics. Geosci Can 1, no 3:54–61
Baragar WRA (1975) Volcanism of the stable crust. In: WRA Baragar LC, Coleman JM Hall: Volcanic regimes in Canada. Geol Ass Canada Sp Pap 16:379–405
Bérrangé JP (1962) The plutonic geology of part of the Grenville Province north of Lake St John, Quebec. Unpubl PhD Thesis, U of London, 451p
Bridgwater D (1967) Feldspathic inclusions in the Gardar igneous rocks of South Greenland and their relevance to the formation of major anorthosites in the Canadian Shield. Can J Earth Sci, 4:995–1014
Bridgwater D, Sutton J, Watterson J (1974) Crustal downfolding associated with igneous activity. Tectonophysics, 57–77
Crosby P (1972) Petrogenesis and significance of Leuconorite in the main Adirondack anorthosite massif. 24th IGC, Montreal, Section 2:312–319
De Waard D (1968) On the origin of anorthosite by anatexis. Ned Kon Akad Wetenschap Proc Ser B, 70:411–419
Doig R, Barton JM (1968) Ages of carbonatites and other alkaline rocks in Quebec. Can J Earth Sci, 5:1401–1407
Duncan PM, Garland GD (1977) A gravity survey of the Saguenay area, Quebec. Can J Earth Sci 14: no 2, 145–152
Emslie RF (1978) Anorthosite massif, Rapakivi granites, and late proterozoic rifting of North America. Prec Res 7:61–98
Emslie RF (1975) Nature and origin of anorthositic suites. Geosci Canada 2:99–104
Frith RA, Currie KL (1976) A model for the origin of the lac St-Jean anorthosite massif. Can J Earth Sci 13:389–399
Frith RA, Doig R (1973) Rb-Sr isotopic ages and petrologic studies of the rocks in the lac St-Jean area, Quebec. Can J Earth Sci 10:881–899
Frith RA, Doig R (1975) PreKenorean tonalitic gneisses in the Grenville Province. Can J Earth Sci Vol 9:652–663
Gagnon G (1979) Le complexe de carbonatite de St-Honoré et ses dépôts de niobium. In: Woussen G, Gagnon G, Bonneau I, Bergeron A, Dimroth E, Roy DW and Thivierge S (eds): Lithologie et tectonique des roches précambriennes et des carbonatites du Saguenay-Lac St-Jean. Guide Book GAC/MAC, Excursion A-3, Lavai University, 16–29
Green DH, Ringwood AE (1967) An experimental investigation of the gabbro to eclogite transformation and its petrological application. Geochim Cosmochim Acta 31:767–833
Green DH, Hiberson W (1969) The instability of plagioclase in peridotite at high pressure. Lithos 3:209–221
Green DH (1969) High pressure experimental studies on the origin of anorthosite. Can J Earth Sci 12:844–849
Grieve RAF, Gittins J (1974) Composition and formation of coronas in the Hadlington gabbro, Ontario, Canada. Can J Earth Sci 18:289–299
Griffin WL (1970) Genesis of coronas in anorthosites of the upper Jotun nappes, Indre Sogn, Norway. J Petrol Vol 12:219–243
Griffin WL, Heir KS (1973) Petrological implications of some corona structures. Lithos 6:315–335
Hocq M (1977) Contribution à la connaissance pétrotectonique et minéralogique des massifs anorthositiques et mangéritiques de la région du réservoir pipmuacan. Unpubl Ph D, thesis, U de Montréal 699p
Holdaway MJ (1971) Stability of andalusite and the aluminium silicate phase diagram. Am J Sci 267:352–370
Irving AJ, Green DH (1970) Experimental duplication of mineral assemblages in basic inclusions of the Delegate breccia pipes. Phys Earth Planet Interiors 3:385–389
Isachsen Y (1969) Origin of anorthosite and related rocks. (Isachsen Y, ed) NY State Mus Sci Ser Mem 18:466p
Jooste RF (1968) Région de Bourget. Ministère des Mines. Québec RG 78:47p
Kehlenbeck MM (1972) Deformation textures in the Lac Rouvray anorthosite mass, Québec. Can J Earth Sci 9:1087–1098
Kumarapelli PS, Saull VA (1966) The St Lawrence Valley System — A North American equivalent to the African Valley Rift Zone. Can J Earth Sci 3:639–658
Kushiro I, Yoder HS (1966) Anorthosite-forsterite and anorthite-enstatite reactions and their bearing on the basalt-eclogite transformation. J Petrol 9:337–362
Laurin AF, Sharma KNM (1975) Mistassini Peribonka, Saguenay Rivers area (Grenville 1965–1967); Que Dept Nat Res Geol Rep 161:89p
Luth WC, Jahns RH, Turtle OF (1964) The granite system at pressure of 4 to 10 kilobars. J Geophys Res 69:759–773
Martignole J, Schrijver K (1970a) Tectonic setting and evolution of Morin anorthosite, Grenville Province, Quebec. Bull Geol Soc Finland 42:165–209
Martignole J, Schrijver K (1970b) The level of anorthosites and its tectonic pattern. Tectonophysics 10:403–409
Mason R (1967) Electron microanalysis of coronas in a troctolite from Solijelma Norway. Mineral Mag 36:504–514
Myers JS, Platt RG (1977) Mineral chemistry of layered Archean anorthosite at Majorgap gâva, near Fiskenaesset, South West Greenland. Lithos 10:59–72
Owen V, Dimroth E, Woussen G (1980) The old gneiss complex east of Chicoutimi. Geol Surv Can Paper 80-1A
Philpotts AR (1966) Origin of the anorthosite-mangerite rocks in Southern Québec. J Petrol 7:1–64
Ramberg H (1967) Gravity, Deformation and the Earth's Crust. Academic Press, London, 214 p
Ryder G (1974) A rationale for the origin of massif anorthosite. Lithos 7:139–146
Schwerdtner WM, Stone D, Osadetz K, Morgan J, Stott GM (1979) Granitoid complexes and the Archean tectonic record in the Southern part of Northwestern Ontario. Can J Earth Sci 16:1965–1977
Schrijver K (1973) Correlated changes in mineral assemblages and in rock habit and fabric across an orthopyroxene isograd, Grenville Province. Quebec. Am J Sci 273:171–186
Sederholm JJ (1967) Selected works; granites and migmatites. Oliver and Boyd ed, 607p
Shand SJ (1945) Coronas and Coronites. Bull Geol Soc Am 56:247–266
Stockwell CH (1964) Fourth report on structural provinces, orogenesis, and time classification of rocks of the Canadian Precambrian Shield. Geol Surv Can, pp 64–17, part II, 1–21
Watterson J (1965) Plutonic development of the llordleg area, South Greenland, Part 1: chronology and the occurrence and significance of metamorphosed basic dykes. Meddr. Grømland Bd 172: Nr 7, 147p
Watterson J (1968) Plutonic development of the llordleg area, South Greenland, Part II: Late Kinematic basic dykes. Meddr Grønland, Bd 173:Nr 3, 103p
Wegmann CE (1928) Über die Tektonik der jüngeren Faltung in Ostfinnland, Fennia 50:16 22p
Wegmann CE (1963) Tectonic patterns at different levels. Geol Soc South Africa annex to volume LXVI, Alex L du Toit memorial lecture 8:78p
Winkler HGF, Von Platen H (1960) Experimentelle Gesteinsmetamorphose III. Anatektische Ultrametamorphose kalkhaltiger Tone. Geochim Cosmochim Acta 18:294–316
Woussen G, Gagnon G, Bonneau J, Bergeron A, Dimroth E, Roy DW, Thivierge S (1979) Lithologie et tectonique des roches précambriennes et des carbonatites du Lac St-Jean. Livret guide A3, GACMAC, Université Laval, Québec, 43 p
Wyllie PJ, Huang WL, Stern CR, Maaloe S (1976) Granitic magmas: possible and impossible sources, water content, and crystallization sequence. Can J Earth Sci 14:1007–1019
Wynne-Edwards HR (1972) The Grenville Province. In: variations in tectonic styles in Canada (eds RA Price and RJW Douglas). Geol Assoc Can Sp Pap 11:263–334
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Woussen, G., Dimroth, E., Corriveau, L. et al. Crystallization and emplacement of the Lac St-Jean anorthosite massif (Quebec, Canada). Contr. Mineral. and Petrol. 76, 343–350 (1981). https://doi.org/10.1007/BF00375461
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00375461