GEOSCAN, résultats de la recherche


TitreTiming of tectonometamorphism across the Green Mountain anticlinorium, northern Vermont Appalachians: 40Ar/39Ar data and correlations with southern Quebec
AuteurCastonguay, S; Kim, J; Thompson, P J; Gale, M H; Joyce, N; Laird, J; Doolan, B L
SourceGeological Society of America Bulletin vol. 124, no. 3/4, 2012 p. 352-367,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100416
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC21E; 21L; 31H; 31I/01; 31I/02; 31I/07; 31I/08; 31I/09
Lat/Long OENS-73.3333 -70.5000 47.0000 42.7333
Sujetsmilieux tectoniques; cadre tectonique; interprétations tectoniques; métamorphisme; datation argon-argon; datations argon-argon; datations radiométriques; Anticlinorium de Green Mountain ; géochronologie; tectonique; géologie structurale; Mésozoïque
Illustrationslocation maps; photomicrographs; cross-sections; plots
ProgrammeBassins sédimentaires d'Hudson / Foxe Bay, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
In the pre-Silurian lithotectonic units of the northern Vermont Appalachians, the timing of orogenesis and tectonometamorphism has traditionally been ascribed to the combined effects of the Middle Ordovician Taconian orogeny and Middle to Late Devonian Acadian orogeny. However, numerous geo chronological studies throughout the Northern Appalachians, including neighboring southern Quebec, have obtained Silurian and Early Devonian age data that document more or less continuous tectonometamorphic activity throughout the Ordovician - Devonian. The structural and metamorphic evolution of northern Vermont can be separated into three regional phases, which are characterized by distinct structures, fabrics, and metamorphic parageneses. The fi rst phase (D1), associated with westward emplacement of various thrust slices leading to crustal thickening and regional metamorphism, and the second phase (D2), characterized by bivergent structures and metamorphic overprint, have both been considered to be Taconian. The third phase, the structure and fabric
of which are also observed in the Silurian - Devonian rocks to the east, is considered to be Acadian. We present new step-heating and spot fusion 40Ar/39Ar geochronological data on amphibole and fabric-forming muscovite from samples taken across the Green Mountain anticlinorium, which, coupled with published data, provide improved age constraints on tectonometamorphism of D1 (latest Cambrian to Middle Ordovician), D2 (Silurian - Early Devonian), and D3 (Middle Devonian) events. By comparing structural and metamorphic characteristics, and now timing, these phases are interpreted to be correlative to the tripartite tectonometamorphic evolution documented in southern Quebec, and they further exemplify the along-strike diachronism of tectonism induced by the inherited irregular geometry of the Laurentian margin.