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TitleArchaean cratonization and deformation in the northern Superior Province, Canada: an evaluation of plate tectonic versus vertical tectonic models
AuthorBédard, J H; Brouillette, P; Madore, L; Berclaz, A
SourceArchaean tectonics, volume 1; by Van Kranendonk, M J (ed.); Precambrian Research vol. 127, issue 1-3, 2003 p. 61-87,
Alt SeriesGeological Survey of Canada, Contribution Series 2002145
Alt SeriesQuebec Department of Natural Resources, Contribution 2002-5130-04
PublisherElsevier BV
MeetingFourth International Archaean Symposium; Perth, Western Australia; AU; September 24 - September 28, 2001
Mediapaper; on-line; digital
File formatpdf
NTS24M; 25C/01; 25C/04; 25C/05; 25C/12; 25C/13; 25C/14; 25D; 25E/01; 25E/02; 25E/03; 25E/04; 25E/05; 25E/06; 25F/03; 25F/04; 34P/01; 34P/02; 34P/07; 34P/08; 34P/09; 34P/10; 34P/15; 34P/16; 35A/01; 35A/02; 35A/06; 35A/07; 35A/08; 35A/09; 35A/10; 35A/11; 35A/14; 35A/15; 35A/16; 35H/01; 35H/02; 35H/03; 35H/06; 35H/07; 35H/08
AreaUngava Peninsula; Ungava Bay; Hudson Straight; lac Peters
Lat/Long WENS -73.2000 -69.2500 61.5000 59.0000
Subjectstectonics; igneous and metamorphic petrology; structural geology; orogenies; craton; terranes; plutons; orogenesis; deformation; plate tectonics; igneous rocks; tonalites; trondhjemites; pyroxene; granodiorites; granites; mafic rocks; magmas; muscovite; epidote; quartz; plagioclase; feldspar; foliation; airphoto interpretation; thin section microscopy; field methods; structural interpretations; thermobarometry; recrystallization; fabric analyses; intrusions; felsic intrusive rocks; shearing; gabbros; norites; hornblende; mica; diorites; monzonites; syenites; metabasalts; charnockites; amphibolites; granulites; layering; lineations; folds; faults; marbles; metasedimentary rocks; monzodiorites; models; ultramafic rocks; mantle; magma differentiation; cumulus processes; Archean; Minto Block; Superior Province; Douglas Harbour Domain; Faribault-Thury Complex; Troie Complex; Qimussinguat Complex; Bottequin Suite; Kapijuq Suite; Lepelle Igneous Complex; McMahon Suite; Diana Complex; Kimber Suite; Curotte belt; Faribault belt, Quebec; Hamelin belt; Kimber belt; Tasiaalujjuaq belt; Thury belt; Thury Deformation Zone; vertical tectonics; cratonization; enderbite; supracrustal rocks; crystal slurries; overprints; resorption; cumulates; restites; extension; Precambrian; Proterozoic
Illustrationsgeological sketch maps; cartoons; photographs; photomicrographs
AbstractThe Archaean Minto Block, northeastern Superior Province, is dominated by tonalite-trondhjemite, enderbite (pyroxene tonalite), granodiorite and granite, with subordinate mafic rocks and supracrustal belts. The plutons have been interpreted as the batholithic roots of Andean-type plate margins and intra-oceanic arcs. Existing horizontal-tectonic models propose that penetrative recrystallization and transposition of older fabrics during terrane assembly at ~2.77 and ~2.69 Ga produced a N-NW tectonic grain. In the Douglas Harbour domain (northeastern Minto Block), tonalite and trondhjemite dominate the Faribault-Thury complex (2.87-2.73 Ga), and enderbite constitutes 50-100 km-scale ovoid massifs (Troie and Qimussinguat complexes, 2.74-2.73 Ga). Magmatic muscovite and epidote in tonalite-trondhjemite have corroded edges against quartz+plagioclase, suggesting resorption during ascent of crystal-charged magma. Foliation maps and air photo interpretation show the common development of 2-10 km-scale ovoid structures throughout the Douglas Harbour domain. Outcrop and thin-section scale structures imply that many plutons experienced a phase of syn-magmatic deformation, typically followed by high temperature sub-magmatic overprints. Thermobarometric data for plutons indicate near-solidus recrystallization at 4-6 kbar pressures. The common preservation of syn-magmatic fabrics in plutons of different ages seems incompatible with the origin of these fabrics through superimposed regional orogenesis. The broad uniformity of intrusion ages and lithologies throughout the Minto Block, and the rarity of shallowly-dipping planar fabrics, also seem inconsistent with accretion of disparate older terranes, each of which should preserve distinct histories. A possible alternative explanation for these features is provided by vertical tectonic models, whereby buoyant felsic magmas ascended as crystal slurries, while dense supracrustal rocks (and solidified felsic intrusions emplaced into them) subsided as cold fingers (10-20 km-scale instabilities). Shear between upwelling and downwelling limbs would have concentrated in the weak intrusions, generating steeply-plunging syn-magmatic fabrics, and producing ductile overprints in solidified rocks.

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