GEOSCAN Search Results: Fastlink


TitlePaleo- to Mesoarchean basement recycling and terrane definition in the Northeastern Superior Province, Québec, Canada.
AuthorBoily, M; Leclair, A; Maurice, C; Bedard, J H; David, J
SourcePrecambrian Research vol. 168, 2009 p. 23-44,
Alt SeriesEarth Sciences Sector, Contribution Series 20080476
Mediapaper; on-line; digital
File formatpdf
NTS23K; 23L; 23M; 23N; 24C; 24D; 24E; 24F; 24K; 24L; 24M; 24N; 25D; 25E; 33I; 33J; 33K; 33L; 33M; 33N; 33O; 33P; 34; 35A; 35B; 35C; 35F; 35G; 35H; 35I; 35J; 35K
Lat/Long WENS-80.0000 -68.0000 62.5000 54.0000
Subjectstectonics; geochemistry; geochronology; Archean; bedrock geology; basement geology; igneous rocks; plutonic rocks; volcanic rocks; volcanism; magmatism; komatiites; tholeiites; plate tectonics; tectonic provinces; tectonic history; tectonic zones; tectonic environments; tectonic interpretations; isotopes; neodymium geochemistry; tonalites; trondhjemites; granodiorites; terranes; Superior Province; enderbites; Precambrian
Illustrationslocation maps; plots
AbstractThe Northeastern Superior Province (NESP) is a 500km×700 km segment of plutonic Archean crust generated by 1.2Ga of tectonomagmatic activity. The NESP exhibits the classical plutonic series of Archean terranes, low-K tonalite - trondhjemite - granodiorite (TTG) and high-K granodiorite - granite - monzogranite (GGM) with unusually large volumes of Px-TTGs (mostly enderbites and subordinate charnockites). Volcanic rocks constitute <10% of the NESP and are dominated by magnesian basalt-komatiite assemblages and bimodal mafic tholeiitic and calc-alkaline felsic tuffs. Mapping, U/Pb geochronological, and Nd isotopic data suggest the presence of two terranes with distinct magmatic histories: the Hudson Bay to the SW, and the Rivière Arnaud to the NE. These terranes are separated by a metasedimentary basin, whichmay be a paleosuture. The Hudson Bay terrane is a Paleo- to Mesoarchean TTG-greenstone craton (3.8 - 2.9 Ga), intruded by 2.76 - 2.74Ga low-K TTGs and younger 2.72 - 2.69 Ga high-KGGMand Px-TTGs that have lowNd isotopic values (epsilonNdT = +0.45 to ?5.03). Mafic to felsic volcanic rocks and mafic to ultramafic plutonic rocks <2.76Ga also have enriched epsilonNdT = +0.40 to?6.90. These radiogenic signatures (as well as inherited zircon cores) record recycling of Mesoarchean (3.8 - 2.9 Ga) crust, either through direct melting, or by coupled assimilation-fractional crystallization processes. In comparison, the Rivière Arnaud terrane is underlain by younger (<3.0 Ga), more juvenile TTG crust, that is intruded by plutons of low-K TTGs (2.79 - 2.76 Ga), high-K GGM (2.73 - 2.72 Ga), and Px-TTGs (2.74 - 2.72 Ga). Most of these rocks have positive to moderately negative epsilonNdT values (+2.34 to ?0.67), indicating either a juvenile character, or recycling of fairly juvenile Late Mesoarchean-Early Neoarchean crust. Overall, geochemical and isotopic data of the Late Neoarchean (<2.76 Ga) low-K TTG and Px-TTG series of the NE Superior Province are not consistent with partial melting solely of juvenile basaltic crust in an oceanic setting. The data are most consistent with remelting of a composite crust constituted of older, isotopically enriched mafic - ultramafic rocks and more juvenile metabasaltic rocks. The basaltic component may have been introduced either by crustal underplating, intra-plating or foundering of supracrustal belts. The mafic melts injected into the maturing cratonic nuclei assimilated the older rocks by an AFC-type process and provided heat. The isotopic and geochemical data imply that the high-K GGM series meltswere produced by melting at shallower depth of an older composite TTG crust, with less involvement of the metabasaltic component.