GEOSCAN, résultats de la recherche


TitreThe tectonometamorphic evolution of Southampton Island, Nunavut: Insight from petrologic modeling and in situ SHRIMP geochronology of multiple episodes of monazite growth
AuteurBerman, R G; Rayner, N; Sanborn-Barrie, M; Whalen, J B
SourcePrecambrian Research vol. 232, 2013 p. 140-166,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110313
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC45O; 46A; 46B; 46C/01; 46C/08; 46C/09; 46C/16; 46F/01; 46F/08; 46F/09; 46F/16
Lat/Long OENS-84.5000 -80.0000 65.5000 63.5000
Sujetsmonazite; thermobarométrie; milieux tectoniques; cadre tectonique; interprétations tectoniques; métamorphisme; zone de roches métamorphiques; orogénies; Craton de Rae ; tectonique; pétrologie ignée et métamorphique; Précambrien
Illustrationslocation maps; tables; Concordia diagrams; phase diagrams; photomicrographs
ProgrammeOr - Baker Lake / Chesterfield Inlet / Wager Bay, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Thermobarometry and in situ SHRIMP monazite geochronology reveal a complex, polycyclic history for Southampton Island, Nunavut, that provides further insights into the assembly of the Nuna supercontinent. Monazite inclusions in garnet from two samples on the western side of the study area define a lower amphibolite- to upper amphibolite-facies M1-D1 event at ca. 1879 ? 8 Ma . These samples, as well as pre-1900 Ma magmatic rocks, occur on the west side of exposed bedrock on Southampton Island, in line with the geophysically defined eastern extent of the Hearne craton beneath Hudson Bay. This timing and geographic distribution are consistent with the model of a Rae-Hearne collision at ca. 1900 Ma, with M1-D1 reflecting reworking of the Rae upper plate following northeast-directed subduction.
The M2-D2 event initiated at 1868 ? 5 Ma at lower amphibolite facies to 1861 ± 4 Ma at upper amphibolite facies. M2-D2 monazite crystallized at upper amphibolite to granulite facies at 1851 ? 5 to 1849 ? 6 Ma in more calcic samples interpreted to have shifted the allanite to monazite reaction to higher temperatures relative to less calcic rocks. Equant matrix monazite that cuts the S2 foliation in one sample documents that post-D2, metamorphism affected the northern part of exposed basement at 1841 ? 4 Ma. Clockwise P-T paths support a collisional setting with the timing of the M2-D2 event in excellent agreement with age constraints on Baffin Island for the accretion of Meta Incognita microcontinent to the southeastern flank of the Rae craton. The Rae craton on Southampton Island is interpreted as the upper plate during this collision on the basis of the geochemistry of pre-M2 magmatic rocks being consistent with an arc setting, textural observations that M2 metamorphism predated D2 deformation, and the ~10 Myr earlier metamorphism on Southampton Island relative to Meta Incognita microcontinent.
Four samples record a post-D2, monazite growth between 1826 ? 9 and 1815 ? 7 Ma that is interpreted to represent a thermal culmination associated with extensive crustal melting and ca. 1.83-1.82 Ga plutonism in a convergent tectonic setting. Exhumation and cooling is loosely dated by ca. 1.80 - 1.79 Ga monazite associated with garnet breakdown.