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TitleNew U-Pb geochronological constraints from mineralized granites in southern Newfoundland
AuthorKerr, A; McNicoll, V
SourceNewfoundland and Labrador, Department of Natural Resources, Geological Survey, Report, Current Research 12-1, 2012 p. 21-38 (Open Access)
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20140466
PublisherNewfoundland and Labrador Department of Natural Resources
Mediaon-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
NTS11P/10; 11P/11; 11P/14; 11P/15; 12B/07
AreaGrey River; Granite Lake
Lat/Long WENS -57.5000 -56.5000 48.5000 47.5000
Subjectsgeochronology; metallic minerals; mineral deposits; tungsten; molybdenum; granitic rocks; uranium lead dates; radiometric dates; vein deposits; metallogeny; mineralization; zircon dates; magmatism; Devonian; Silurian
Illustrationsgeological sketch maps
ProgramTargeted Geoscience Initiative (TGI-4), Intrusion/Porphyry Ore Systems
AbstractThis 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.