Uranium-lead geochronology of metamorphic accessory minerals south of the Grenville Front, western Québec, Canada

• Main Author: Childe, Fiona
• Format: Others
• Language: en
• Published: McGill University 1992
• Subjects: Geology.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61060

U-Pb ages were determined on single grains of monazite and xenotime as well as small populations of rutile from amphibolite to granulite facies metasediments of the Quebec Gneiss Segment of the Grenville Province in an area extending 45 to 135 km south of the Grenville Front in La Verendrye Park, Quebec. Recent geochronological studies include Pb-isotope ratios of metamorphic minerals corresponding to ages of 2.5 to 2.65 Ga and U-Pb monazite ages to 2649 to 2655 Ma, which define a lower discordia intercept of approximately 1.01 Ga. Recent thermobarometric studies indicate the presence of two metamorphic episodes in the region. === Monazite and xenotime grains obtained from high grade metasediments at five locations between 45 and 70 km southeast of the Grenville Front yielded $ sp{207}$Pb/$ sp{206}$Pb ages of 999 $ pm$ 5 Ma to 1021 $ pm$ 2 Ma. Monazite from the norther part of this terrane also defined an upper intercept age of 2596 $ pm$ 3 Ma. === The southernmost sample location, 135 km south of the Grenville Front, yielded both monazite and rutile. Monazite gave an age of 1072 $ pm$ 2 Ma. Small populations of rutile yielded an age of 916 $ pm$ 2 Ma. (Abstract shortened by UMI.)