Geology and U-Pb geochronology of the Kipawa syenite complex; a thrust related alkaline pluton and adjacent rocks in the Grenville Province of western Quebec

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doi: 10.1139/e04-010
Authors:van Breemen, O.; Currie, K. L.
Author Affiliations:Primary:
Geological Survey of Canada, Ottawa, ON, Canada
Volume Title:Canadian Journal of Earth Sciences Revue Canadienne des Sciences de la Terre
Source:Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 41(4), p.431-455. Publisher: National Research Council of Canada, Ottawa, ON, Canada. ISSN: 0008-4077
Publication Date:2004
Note:In English with French summary. Geol. Surv. Can., Contrib. No. 2003189. 52 refs.; illus., incl. 8 tables, geol. sketch map
Summary:The Kipawa Syenite Complex, a thin, folded sheet of amphibole syenite, quartz syenite and minor nepheline syenite, lies along a west-vergent thrust separating a lower slice comprising the Kikwissi granodiorite and biotite tonalite dated at 2717+15-11 Ma, and unconformably overlying metasedimentary rocks from an overlying slice containing the Red Pine Chute orthogneiss, and alkali granite gneiss, and the Mattawa Quartzite. The syenite complex, dated at 1033±3 Ma, lies within the lower slice but has metasomatically altered the overlying slice. Texturally guided U-Pb spot analyses on partially metasomatised zircons from the alkali granite gneiss yield a cluster of 207Pb/206Pb ages at 1389±8 Ma, interpreted as the time of igneous crystallization and four ages overlapping the time of syenite emplacement, interpreted as in situ, metasomatic growth. The highest structural slice comprises garnet amphibolite separated from lower slices by the Allochthon Boundary Thrust. Metamorphic grade increases upward from greenschist grade in the biotite tonalite to amphibolite grade (690°C, 9 kbar (1 kbar = 100 MPa) at the lower boundary of the alkali granite. Emplacement of the Kipawa Syenite Complex took place after assembly of the thrust stack had begun and after emplacement of the allochthon or hot slab responsible for the inverted metamorphic gradient. Origin of the syenite is tentatively ascribed to anatexis of material metasomatized by flow of alkaline solutions along a major shear surface. Crystallization of new zircon in the margins of the syenite shows that metasomatism continued from ca. 1035 to 990 Ma, redistributing alkalies, fluorine, rare-earth elements and zirconium.
Sections:Age determination; Petrology
Subsections:Igneous petrology
Subjects:Absolute age; Alkalic composition; Chemical composition; Dates; Dikes; Faults; Geochemistry; Granites; Igneous rocks; Intrusions; Mesoproterozoic; Metamorphism; Metasomatism; Mineral composition; Nesosilicates; Orthosilicates; Plutonic rocks; Plutons; Precambrian; Proterozoic; Silicates; Syenites; Tectonic elements; Thrust faults; Trace elements; U/Pb; Upper Precambrian; Zircon; Zircon group; Canada; Canadian Shield; Eastern Canada; Grenville Province; Kipawa Lake; North America; Quebec; Temiscamingue County Quebec; Kikwissi Suite; Kipawa Complex; Mattawa Quartzite; Western Quebec
Coordinates:N484500 N484500 W0783000 W0783000
Abstract Numbers:04M/2718
Record ID:2004056575
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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