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TitleZircon U-Pb geochronology of the Ottawa Orogeny, Adirondack Highlands, New York: regional and tectonic implications
AuthorMcLelland, J; Hamilton, M; Selleck, B; McLelland, J; Walker, D; Orrell, S
SourcePrecambrian Research vol. 109, 2001 p. 39-72,
LinksAbstract - Résumé
Alt SeriesGeological Survey of Canada, Contribution Series 200037
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNew Brunswick; Newfoundland and Labrador; Ontario; Quebec
NTS12D/04; 12D/05; 12D/06; 12D/10; 12D/11; 12D/12; 12D/13; 12D/14; 12D/15; 12D/16; 12E; 12F/04; 12F/05; 12F/06; 12F/10; 12F/11; 12F/12; 12F/13; 12F/14; 12F/15; 12F/16; 12J/04; 12J/05; 12J/06; 12J/10; 12J/11; 12J/12; 12J/13; 12J/14; 12J/15; 12J/16; 12K; 12L; 12M; 12N; 12O; 12P/04; 12P/05; 12P/06; 12P/10; 12P/11; 12P/12; 12P/13; 12P/14; 12P/15; 12P/16; 13; 22; 23; 31B; 31C; 31D; 31E; 31F; 31G; 31H; 31I; 31J; 31K; 31L; 31M; 31N; 31O; 31P; 32
AreaOttawan Orogeny
Lat/Long WENS -80.0000 -56.0000 56.0000 44.0000
Subjectsgeneral geology; geochronology; igneous and metamorphic petrology; structural geology; tectonics; orogenesis; orogenies; orogenic regions; plate tectonics; tectonic environments; deformation; metamorphism; folding; geochronometry; zircon; lead uranium ratios; uranium lead dates; uranium lead dating; dykes; pegmatites; granites; granitic rocks; radiometric dates; zircon dates; gneisses
Illustrationslocation maps; sketch maps; geological sketch maps; tables; photographs; photomicrographs; geochemical plots; geological time charts; time series; schematic diagrams
Released2001 06 01
AbstractBoth single and multigrain U-Pb zircon thermal ionization mass spectrometry (TIMS) as well as sensitive high
resolution ion microprobe (SHRIMP ll) dating of two suites of Adirondack granites have yielded ages constraining
the principal tectonomagmatic events of the Ottawan Orogeny to the interval ca 1090–1035 Ma. The earliest of these
consists of mildly A-type hornblende granites of the Hawkeye granite suite, multigrain samples of which define a tight
age cluster of ca 1103–1093 Ma. Assemblages and fabrics in this suite demonstrate that it experienced the high-grade
effects of the Ottawan Orogeny, thereby fixing the maximum age of the latter at ca 1090 Ma. The second suite
consists of Lyon Mt. Granitic Gneiss, six samples of which cluster tightly at ca 1060–1045 Ma. Fabrics associated
with this suite indicate a late- to post-tectonic origin thus fixing the minimum age for the Ottawan Orogeny.
Especially critical are two samples of ca 1047 Ma fayalite granite that are essentially undeformed and must post-date
tectonism. In addition, an undeformed pegmatite dike yields an age of 1034\'018 Ma confirming the termination of
Ottawan orogenesis by that time. It is suggested that the genesis of the Hawkeye suite is related to athenospheric
heating of the crust due to far-field effects of contemporaneous magmatic events at the Midcontinent rift. Lyon Mt.
Granitic Gneiss is interpreted as the result of deep crustal melting following delamination of the overthickened
Ottawan orogen. Together with the results of metamorphic investigations, these two suites define a counterclockwise
P–T–t loop for the Adirondacks during the Ottawan Orogeny. Geochronological and tectonic investigations from the
Grenville Province of Canada and the northern Blue Ridge Province of the Appalachians demonstrate the presence
of strong Ottawan deformation, magmatism, and metamorphism in these areas and emphasize the large scale and
marked intensity of this event. In Canada, the crust responded to the Ottawan collision principally by imbricating

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