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TitreNew U-Pb geochronological constraints from mineralized granites in southern Newfoundland
AuteurKerr, A; McNicoll, V
SourceNewfoundland and Labrador, Department of Natural Resources, Geological Survey, Report, Current Research 12-1, 2012 p. 21-38 (Accès ouvert)
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140466
ÉditeurNewfoundland and Labrador Department of Natural Resources
Documentpublication en série
Mediaen ligne; numérique
SNRC11P/10; 11P/11; 11P/14; 11P/15; 12B/07
Lat/Long OENS -57.5000 -56.5000 48.5000 47.5000
Sujetsgisements minéraux; tungstène; molybdène; roches granitiques; datations au uranium-plomb; datations radiométriques; gisements filoniens; métallogénie; minéralisation; datations au zircon; magmatisme; géochronologie; minéraux métalliques; Dévonien; Silurien
Illustrationsgeological sketch maps
ProgrammeÉtude des gîtes porphyriques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
This article reports U-Pb SHRIMP geochronological data from granitic rocks associated with W and Mo-Cu mineralization
in the Grey River and Granite Lake areas of southern Newfoundland. The Grey River area hosts a vein-style tungsten
deposit, and numerous minor base- and precious-metal bearing veins. A potentially large Mo-Cu deposit (Moly Brook) consisting
of sheeted mineralized quartz veins is now also defined by recent exploration activity. It has long been speculated that
this diverse metallogeny is genetically linked to a largely hidden younger intrusion. The granodioritic host rocks to the
Mo-Cu-bearing vein system gave an age of 411 ± 4 Ma, but fine-grained alaskitic granites that contain disseminated molybdenite
gave a much younger age of 378 ± 4 Ma. Field evidence suggests a contemporaneous relationship between alaskitic
granites and the mineralized veins, indicating that veins also formed at ca. 378 Ma. Mineralization at Moly Brook thus postdates
its immediate host rocks by >30 m.y., i.e., it is epigenetic. The age interpreted for alaskitic granites and mineralization
matches that obtained from the François Granite, a geochemically evolved pluton located about 20 km to the east. The age
also overlaps with ages from two other granitoid plutons associated with granophile mineralization in southern Newfoundland.
At Granite Lake, Mo-bearing veins are hosted by an equigranular biotite-muscovite granite that also contains disseminated
molybdenite, and locally displays intense advanced argillic alteration. The biotite-muscovite granite is thought to be
contemporaneous with mineralization. The U-Pb zircon data from the granite suggest an age of 388 ± 4 Ma, and indicate
inherited cores of both Silurian (427-417 Ma) and Paleoproterozoic age. If this also records the timing of mineralization, it represents a slightly older episode of metallogenesis than that at Grey River. It is possible that there is a regional age variation amongst mineralized granites from northwest to southeast, but many more data are needed to confirm this hypothesis.