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TitreGeology and Geochemistry of Middle Jurassic and Early Cretaceous Igneous Rocks On the eastern North American Continental Shelf
AuteurJansa, L F; Pe-Piper, G
SourceCommission géologique du Canada, Dossier public 1351, 1986, 104 pages, (Accès ouvert)
Documentdossier public
Mediapapier; en ligne; numérique
Référence reliéeCette publication est reliée Pe-Piper, G; Piper, D J W; Imperial, A; (2018). Electron microprobe mineral analyses from Carboniferous to Cretaceous igneous rocks offshore southeastern Canada and northeastern U.S.A., Commission géologique du Canada, Dossier public 8357
ProvinceNunavut; Région extracotière du nord; Québec; Nouvelle-Écosse; Île-du-Prince-Édouard; Nouveau-Brunswick; Ontario; Région extracotière de l'est; Terre-Neuve-et-Labrador
SNRC11; 20O; 20P; 21; 12A; 12B; 12C; 12D; 12F; 12G; 12H; 12I; 12P; 1; 2; 3; 15E; 15K; 15L; 15M; 15N; 25P; 25O/16; 26A; 26H; 26I; 26J; 26O; 26P; 27A; 120B; 120C; 120F; 39G; 340A; 340B; 340C; 340D; 340E; 340F; 49F; 49G; 49H; 59C; 59E; 59F; 59G; 59H; 560A; 560B; 560D; 69; 79A; 79C; 79D; 79E; 79F; 79H; 13A; 13H; 13I; 13J; 13O; 13P; 22A; 30; 31B; 31C; 31G; 31H; 31I; 40G; 40I
Lat/Long OENS -67.0000 -58.0000 72.0000 61.0000
Lat/Long OENS-112.0000 -66.0000 83.0000 76.0000
Lat/Long OENS -84.0000 -36.0000 60.0000 35.0000
SujetsJurassique moyen; basaltes; roches mafiques; Crétacé inférieur; filons rocheux; filons-couches; diabases; analyses pétrographiques; analyses de la roche, éléments majeurs; manteau terrestre; zones de fracture; tectonique de plaques; analyses structurales; analyses de la roche, éléments de terres rares; datation au potassium-argon; Plate-Forme du Labrador; Plate-Forme de Néo-écossaise; Chaîne Mont sous-Marin de Terre-Neuve; géochimie; géologie régional; Jurassique; Crétacé
Illustrationslocation maps; stratigraphic columns
Points de vente
Precision Document Management
174 Trider Crescent, Burnside Industrial Park, Halifax, NS B3B 1R6; Ph. 902-455-5451; Fax. 902-442-4145,
Diffusé1986 10 01; 2011 12 22
Résumé(disponible en anglais seulement)
Late Middle Jurassic and Early Cretaceous mafic dykes, sills, flows and locally associated volcaniclastics occur from the Baltimore Canyon Trough northwards to the Labrador Shelf. The late Middle Jurassic activity was of a short duration at about 140 m.y. and is documented here from the Georges Bank. The Cretaceous igneous activity, which is more regionally widespread, continued for about 40 m.y. (95-135 m.y.). All the rocks analysed are alkali basalts and related mafic rocks. Rocks from the Baltimore Canyon, Georges Bank and New England Seamounts show marked enrichment in light REE and many incompatible trace elements, and appear to have been derived by a small amount of partial melting of enriched mantle of the type associated with mantle plumes. In contrast, rocks from the Scotian Shelf and Grand Banks show slightly convex REE spectra and less enrichment in incompatible elements and appear to be derived from normal (non-enriched) mantle. Limited data for the Newfoundland Seamounts suggests that they are associated with a slightly enriched mantle source. The regional geochemical differences noted between the Grand Banks - Scotian Shelf igneous province and the Georges Bank - Baltimore Canyon igneous province may reflect basic differences in mantle composition and evolutionary history. This may be related to; the development of a mantle plume beneath the Georges Bank - Baltimore Canyon trough province. The Cretaceous volcanism coincides with reactivation and formation of fracture zones as a result of changes in plate stresses culminating in
separation of the Grand Banks and Iberia and initiation of rifting in the Labrador Sea.
The late Middle Jurassic igneous activity on Georges Bank led to the construction of several volcanic cones. The regional distribution of the volcanic ash suggests prevailing offshore winds, blowing to the east. The occurrence of both Middle Jurassic and Early Cretaceous buried volcanoes under the upper continental slope off Georges Bank sheds new light on the origin of the New England Seamount chain. An initial shear failure, which probably penetrated the uoper mantle focussed on regional stresses to develop a propagating fracture zone which became the loci of igneous activity at its propagating tip. After decoupling of the continental plates and the initiation of seafloor spreading in the Labrador Sea (83-92 m.y.), the igneous activity ceased along the eastern North American margin and at the propagating tip of the New England Seamount fracture zone.