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TitreU-Pb age and Hf-isotope geochemistry of zircon from felsic volcanic rocks of the Paleoproterozoic Aillik Group, Makkovik Province, Labrador
AuteurLaflamme, C; Sylvester, P J; Hinchey, A M; Davis, W J
SourcePrecambrian Research vol. 224, 2013 p. 129-142, https://doi.org/10.1016/j.precamres.2012.09.005
Année2013
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120198
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.precamres.2012.09.005
Mediapapier; en ligne; numérique
Formatspdf
ProvinceTerre-Neuve-et-Labrador
Lat/Long OENS-63.0000 -59.5000 55.5000 54.0000
Sujetsdatations au uranium-plomb; datation au uranium-plomb; rapports uranium-plomb; magmatisme; roches ignées; roches volcaniques; études de la croûte; evolution de la croûte; méthodes analytiques; analyse par spectromètre de masse; Groupe d'Aillik ; Province de Makkovik ; géochimie; géochronologie; Précambrien; Protérozoïque
Illustrationslocation maps; photographs; plots; photomicrographs; histograms
ProgrammeUranium, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
U-Pb zircon SHRIMP geochronology and Lu-Hf zircon LA-MC-ICPMS isotope geochemistry are used to constrain the ages of Paleoproterozoic felsic magmatism and their crustal sources in the Aillik Group, Makkovik Province of Labrador. This information is important for understanding the extent of crustal reworking vs. juvenile crustal growth in subduction-related magmatism during the Paleoproterozoic. U-Pb SHRIMP zircon geochronology from four felsic tuff samples collected from two different areas of the Aillik Group yield magmatic 207Pb/206Pb ages of 1852 ± 7 Ma, 1854 ± 7 Ma, 1861 ± 7 Ma, and 1862 ± 7 Ma. The ages fall within the range of previous U-Pb zircon dates reported for felsic volcanic rocks of the Aillik Group, which, altogether, indicate that felsic volcanism occurred over 30 m.y., and was perhaps concentrated during the last 10 m.y. of that interval. A foliated syn-deformational monzogranite in the Aillik Group (Cross Lake granite) yields a 207Pb/206Pb zircon date of 1805 ± 6 Ma, which indicates that development of a pervasive planar fabric associated with northwestward thrusting of the Aillik Group continued after this time.
Initial values for magmatic zircons from the felsic tuffs and monzogranite range from -11.8 to +3.8, indicating heterogeneous sources. Most of the zircon grains have negative initial values and calculated crust formation Hf-isotope TDM model ages point to substantial contributions from melts of ancient crust, ranging in age from ca. 2200 to 2900 m.y. and clustering at ca. 2500 m.y. Inherited zircon grains in the felsic tuffs and monzogranite, mainly have U-Pb ages of ca. 1880 to 1920 Ma, though others are older, up to ca. 2743 Ma. Hf-isotope TDM model ages for the inherited zircons are similar to those of the magmatic zircons. The Hf-isotope results indicate that subduction-related magmatism in the Makkovik Orogen involved significant amounts of crustal reworking during formation of the Aillik Group.
GEOSCAN ID291839