ND ISOTOPIC EVIDENCE FOR CRUSTAL RECYCLING IN THE CA 2.0 GA SUBSURFACE OF WESTERN CANADA

Sm-Nd isotopic data are presented for 23 drill-core samples from five aeromagnetically and geochronologically (U-Pb zircon) distinct domains of the Precambrian basement of northern Alberta. The domains in question are the Taltson (1.96-1.94 Ga), Buffalo Head (2.32-1.99 Ga), Chinchaga (2.19-2.09 Ga), Ksituan (1.99-1.90 Ga), and Nova (2.81 Ga). These domains are truncated to the north and south by the Great Slave Lake shear zone and the Snowbird tectonic zone, respectively. Initial epsilon-Nd values are -5.0 to -9.7 for the Taltson, +0.2 to -6.3 for the Buffalo Head, +0.6 to -1.8 for the Chinchaga, -1.8 to -2.1 for the Ksituan and +5.6 for the Nova. Crustal residence model ages fall in the 2.5-2.8 Ga range. The Nd isotopic signatures may be viewed in terms of mixing a minimum of 10% Archean continental crust with a depleted-mantle component. Speculations on the tectonic history of the basement domains in question involve the assembly of Archean crustal nuclei to form the Buffalo Head - Chinchaga composite domain. Arc magmatism resulting from plate subduction to the east and west of the Buffalo Head - Chinchaga composite domain would have generated the Taltson and Ksituan domains. The Nd isotopic data suggest that the basement of northern Alberta consists of crust of late Archean crustal residence age which has been extensively remobilized in the Early Proterozoic.