U-Pb geochronology of the Grenville Orogen of Ontario and New York: constraints on ancient crustal tectonics
نویسنده
چکیده
Based on lithological, structural and geophysical characteristics, the Proterozoic Grenville Orogen of southern Ontario and New York has been divided into domains that are separated from each other by ductile shear zones. In order to constrain the timing of metamorphism, U-Pb ages were determined on metamorphic and igneous sphenes from marbles, calc-silicate gneisses, amphibolites, granitoids, skarns and pegmatites. In addition, U-Pb ages were obtained for monazites from metapelites and for a rutile from an amphibolite. These mineral ages constrain the timing of mineral growth, the duration of metamorphism and the cooling history of the different domains that make up the southern part of the exposed Grenville Orogen. Based on the ages from metamorphic minerals, regional and contact metamorphism occurred in the following intervals: Central Granulite Terrane: Adirondack Highlands: 1150 Ma; 1070-1050 Ma; 1030-1000 Ma Central Metasedimentary Belt: Adirondack Lowlands Frontenac domain Sharbot Lake domain Elzevlr domain: Bancroft domain: Central Gneiss Belt:
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