Structural development of the Snow Lake Allocnthon and its role in the evolution of the southeastern Trans-Hudson Orogen in Manitoba, central Canada

摘要

The Snow Lake Allochthon is a zone of tectonicinterleaving of sedimentary rocks of an inverted marginal basin(Kisseynew Domain) with island-arc and oceanic rocks. It islocated in the southeastern part of the exposed internal zone ofthe Paleoproterozoic Trans-Hudson Orogen in Manitoba,Canada, near the external zone (Superior collision zone orThompson Belt), which constitutes the local boundary betweenthe Trans-Hudson Orogen and the Archean Superior Craton. TheSnow Lake Allochthon formed, was deformed, and wasmetamorphosed up to high grade at low to medium pressureduring the Hudsonian orogeny as a result of the collision ofArchean cratons ~1.84-1.77 Ga. Four generations of folds (F_1-F_4) that formed in at least three successive kinematic framesover a period of more than 30 Ma are described. Isoclinal totransposed southerly verging F_(1-2) structures are refolded bylarge, open to tight F_3 folds and, locally, by open to tight F_4folds. The axes of the F_(1-2) folds are parallel or near parallelto the axes of F_3 folds, owing to progressive reorientation ofthe F_(1-2) axes during south- to southwest-directed tectonictransport, followed by F_3 refolding around the previous linearanisotropy. A tectonic model is presented that reconciles thedistinct tectono-metamorphic developments in the Snow LakeAllochthon and the adjacent part of the Kisseynew Domain onthe one hand, and in the Thompson Belt on the other, duringfinal collision of the Trans-Hudson Orogen with the Superior Craton.