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TitreGeochemistry and origin of the Neoproterozoic Natkusiak flood basalts and related Franklin sills, Victoria Island, Arctic Canada
AuteurBeard, C D; Scoates, J S; Weis, D; Bédard, J H; Dell'Oro, T A
SourceJournal of Petrology vol. 58, no. 11, 2017 p. 2191-2220, https://doi.org/10.1093/petrology/egy004
Année2017
Séries alt.Ressources naturelles Canada, Contribution externe 20170137
ÉditeurOxford Academic
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1093/petrology/egy004
Mediapapier; en ligne; numérique
Formatspdf; html
ProvinceTerritoires du Nord-Ouest; Nunavut
SNRC77G; 78B; 87E; 87F; 87G; 87H; 88A; 88B
Lat/Long OENS-120.0000 -108.0000 73.0000 70.5000
Sujetsgéologie du substratum rocheux; lithologie; roches ignées; roches volcaniques; basaltes; roches intrusives; roches granitiques; gabbros; roches sédimentaires; caractéristiques structurales; failles; plis; synclinaux; anticlinaux; évolution tectonique; evolution de la croûte; magmatisme; intrusions; filons-couches; filons rocheux; cristallisation fractionnée; mise en place; altération; analyses des roches totales; etudes isotopiques; plomb; strontium; néodyme; hafnium; olivine; géochimie du niobium; géochimie du lanthane; datations au neodymium-samarium; régions émettrices; croûte continentale; croûte océanique; manteau terrestre; analyses des éléments en trace; analyses des éléments majeurs; dynamique des fluides; interprétations géophysiques; interprétations magnétiques; analyses pétrographiques; établissement de modèles; Formation de Natkusiak ; Rodinie; Supergroupe de Shaler ; Orogenèse de Wopmay ; Formation de Kuujjua ; Formation de Kilian ; Formation de Wynniatt ; Formation de Minto Inlet ; Groupe de Reynolds Point ; Groupe de Rae ; géochimie; pétrologie ignée et métamorphique; tectonique; Précambrien; Protérozoïque
Illustrationsgeoscientific sketch maps; location maps; photographs; lithologic sections; geochemical profiles; geochemical plots; tables; schematic cross-sections
ProgrammeLIP de l'haut-Arctique de l'ouest de l'Arctique, GEM2 : La géocartographie de l'énergie et des minéraux
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
Diffusé2018 01 30
Résumé(disponible en anglais seulement)
The Natkusiak continental flood basalts and Franklin sills of Victoria Island preserve an exceptional record of the ca. 716-723 Ma Franklin large igneous province and are synchronous with major climatic variations and breakup of the supercontinent Rodinia. The Natkusiak Formation basalts record an early phase of discontinuous rubbly flows (<100m, low-Ti Type 1 magmas) overlain by a thicker series of extensive tholeiitic sheet flows (~1100m, high-Ti Type 2 magmas). Coeval intrusions hosted by underlying Shaler Supergroup sedimentary rocks are differentiated low-Ti Type 1 Franklin sills and doleritic high-Ti Type 2 sills, both of which show correlations in isotope plots with the northernmost basalts on Victoria Island. Whole-rock Pb-Sr-Nd-Hf isotopic compositions from 66 samples indicate that the earliest magmas (Type 1) had similar primary melt compositions (Fo90 olivine) to oceanic island basalts and incorporated up to 10% granitoid basement (initial epsilon(Nd)= -0.8 to -7, Nb/La= 0.42 to 0.67), a relatively weak continental signature compared to many other continental flood basalt provinces. Type 2 doleritic sills and the northern sheet flow basalts incorporated up to 5% granitoid (initial epsilon(Nd)= +0. 9 to+5.5), consistent with a waning continental influence during maturation of the magmatic system. Radiogenic isotope ratios are not correlated with indices of fractional crystallisation, which indicates that the continental material was either dispersed within the melt source, or that the magmas were heterogeneously contaminated prior to differentiation. In the southwestern part of Victoria Island, Type 1 basalts show negligible continental influence (Nb/La= 0.81 to 0.94) and have unusually high initial epsilon(Nd) ratios (+4.4 to +11.8) that are decoupled from initial epsilon(Hf) (+0.8 to +11.1). These radiogenic epsilon(Nd) compositions persist throughout the southern volcanic stratigraphy and indicate involvement of a component with high time-integrated Sm/Nd that lacked correspondingly high Lu/Hf. We propose that the source region for the southwestern Natkusiak basalts and related sills included isotopically matured oceanic crust, which was recycled through the asthenospheric mantle into a laterally heterogeneous plume. The distinct trace element signatures of the southern and northern sources became attenuated with the onset of voluminous melting (corresponding to emplacement of the Type 2 doleritic sills and sheet flow basalts) and may reflect contributions from hydrous eclogitic material emplaced into the lithospheric mantle during the ca. 1.9 Ga Wopmay Orogeny. As both the northern and southern volcanic rocks exhibit contrasting isotopic signatures throughout the preserved stratigraphy, the magma plumbing system must have experienced limited lateral mixing and homogenisation, which allowed for the expression of distinct mantle source signatures in the high-level sills and basaltic lavas.
Résumé(Résumé en langage clair et simple, non publié)
Les données isotopiques impliquent que la source du manteau de Franklin magmas avait un composant plus ancien et que le système de plomberie était compartimenté, de sorte que les N lavas diffèrent de S lavas.
GEOSCAN ID305009