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TitreMorphology, petrography, age and origin of the Fogo Seamounts, eastern Canada
TéléchargerTéléchargements
AuteurPe-Piper, G; de Jong, A; Piper, D J W; Jansa, L F
SourceCommission géologique du Canada, Dossier public 5182, 2006, 74 pages, https://doi.org/10.4095/221822 (Accès ouvert)
Image
Année2006
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/221822
Mediapapier; en ligne; numérique
Formatspdf
ProvinceRégion extracotière de l'est
Lat/Long OENS-55.0000 -50.0000 45.0000 40.0000
Sujetsmarges continentales; marges continentales, atlantique; talus continental; cadre tectonique; failles transformantes; marges plaques; bathymétrie; levés géophysiques; levés de reflexion sismiques; profils sismiques; levés magnétiques; échantillonnage par drague; pétrographie; antécédents géologiques; roches ignées; roches volcaniques; basaltes; pyroxene monoclinique; olivine; géochimie du magnesium; métaux; analyses des éléments en trace; etudes isotopiques; manteau terrestre; datation radiométrique; datations argon-argon; datation au potassium-argon; roches sédimentaires; trangressions; submersion; érosion côtière; affaissement; carbonate; analyses des éléments majeurs; changements du niveau de la mer; volcanisme; monts sous-marins; magmatisme; tholéiites; alcalinité; Puit Narwhal F-99 ; géologie marine; pétrologie ignée et métamorphique; géochimie; géochronologie; Phanérozoïque; Cénozoïque; Mésozoïque; Crétacé
Illustrationssketch maps; cartoons; profiles; geophysical maps; well logs; biostratigraphic sections; photographs; graphs; geochemical plots; ternary diagrams; tables
ProgrammeLe Programme de recherche et de développement énergétiques (PRDE)
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
Diffusé2006 03 01; 2009 10 21
Résumé(disponible en anglais seulement)
The Fogo Seamounts are located approximately 500 km offshore from Newfoundland to the southwest of the Grand Banks of Newfoundland. This complex seamount chain is Early Cretaceous in age and is partially buried under later continental slope deposits. The seamounts are developed along the northeastern transform margin of the Jurassic central Atlantic Ocean. The Narwhal F-99 well was drilled in 1986 on the continental slope into one buried seamount. In this study, we have compiled unpublished data on the bathymetry, seismic-reflection character, and distribution of the Fogo Seamounts and interpret new petrographic, geochemical and geochronological data from a dredge sample from seamount G in the central part of the seamount chain and from the Narwhal F-99 well. Petrographically, the seamount samples consist of vitrophyric basalt, with clinopyroxene at Narwhal and kaersutite in the dredge sample. Chemically, the samples are olivine basalt with a low Mg number and low concentration of transition metals. Trace element and REE abundances are similar to those of other early Cretaceous volcanic rocks on the southeast Canadian margin, except that LILE are more enriched in basalts on the continental shelf. Sm/Nd isotopes suggest mantle derivation, with ,Nd ranges from 2.3 to 4.7. Overall, the Narwhal basalts are more tholeiitic whereas the basalts at seamount G are more alkalic, showing OIB characteristics, and their range of compositions is well matched by basalts from Hawaii. The dredge sample at seamount G gave a 40Ar/39Ar age of 130.3 ± 1.3 Ma on kaersutite (top Hauterivian on the Gradstein et al. 2004 time scale). A K/Ar age from the Narwhal F-99 well of 127 ± 6 Ma is inconsistent with biostratigraphic zonation, which shows that sedimentary rocks overlying basalt in the well are at least as old as early Berriasian (ca. 145 Ma). Seismic reflection profiles show that a series of coastal transgressions can be recognised above the basalt, with final submergence probably in the Berriasian. Distribution of the seamounts, based on bathymetry and in the case of buried seamounts, magnetic and seismic data, shows that there is no clear linear trend, but rather a broad zone within which seamounts have formed. New bathymetric data shows that flat tops to seamounts, resulting from coastal erosion prior to subsidence and platform carbonate deposition, show no systematic pattern. The broad extent of the seamounts on the margin probably results from the influence of a series of upper crustal faults along the transform margin.
GEOSCAN ID221822