Neoarchean evolution of the western-central Wabigoon boundary zone, Brightsand Forest Area, Ontario.

Abstract

The boundary between the western and central domains of the Wabigoon subprovince has been considered to represent a ca. 2.7 Ga suture between juvenile Neoarchean volcanic rocks in the west and granitoid rocks with Mesoarchean ancestry in the central Wabigoon. The nature and timing of interaction between these two terranes was examined southeast of the Sturgeon Lake greenstone belt within the central Wabigoon, where amphibolite-facies supracrustal remnants are dismembered by Neoarchean plutonic rocks and shear zones. Of the 4 preserved ductile deformation fabrics, D1 and D2 are bracketed by a 2718 +/- 7 Ma tonalite gneiss and crosscutting 2715 Ma tonalite dyke. The main penetrative S3 foliation affects most units, including quartz-rich sandstone deposited after 2701 Ma. A 2697 Ma granodiorite dyke cutting S3 in mafic and metasedimentary rocks provides a lower bracket on D3. Regional implications can be drawn from the observation of 2725--2715 Ma D1 and D2 deformation events in the central Wabigoon. These constraints overlap with an early deformation event in the Pipestone Lake area of the western Wabigoon (2727--2712 Ma; Edwards and Stauffer, 1999). (Abstract shortened by UMI.)