Emplacement and deformation features of syntectonic leucocratic veins from Rainy Lake zone (Western Superior Province, Canada)

Abstract

Networks of leucocratic veins are widespread in the Rice Bay–Redgut Bay domain of the Rainy Lake zone at the Wabigoon–Quetico subprovince boundary (Archean Superior Province, Canada). Vein geometries and their cross-cutting relationships with host rocks are indicative of syntectonic emplacement within a regional late Archean transpressional deformation event (Kenoran orogeny). The relative folding and boudinage of the veins compared to their host rocks indicate that they were emplaced syntectonically with the D 2 deformation. Semi-quantitative strain and vorticity analyses confirm the syn-D 2 timing of the veins. The observed structural features are interpreted as being formed during magma emplacement along dilatant fractures and subsequent solid-state deformation under overall ductile deformation conditions. The structures related to emplacement are better preserved in domains of low post-emplacement strain and veins intruded into competent host rocks, whereas the folds and boudins related to post-emplacement deformation are well developed in veins intruded into relatively incompetent host rocks. In domains of high strain, the primary intrusive structures are modified or even locally obliterated due to increasing deformation. It is envisaged that regional kinematics and the rheological state of host rocks are the main controls on the style of vein emplacement and deformation. The variety of observed structures is considered the result of deformation and lithological heterogeneity rather than several distinct magmatic events.