Structure of Ahmic domain and its vicinity, southwestern Central Gneiss Belt, Grenville Province of Ontario (Canada)☆

摘要: Abstract In the Central Gneiss Belt of Ontario (CGB), parautochthon and a stack four thrust sheets have been transformed into complex system inclined upright folds. One large structure, 50 km long Wahwashkesh-Ahmic Lakes antiform (WALA), folds three represented by rock assemblages in Ahmic, Parry Sound or Shawanaga domains. Despite its tight map pattern west Magnetawan village, WALA is gentle to open, disharmonic, noncylindrical, buckle fold that deforms main foliation other ductile-style mesoscopic structures Grenville gneisses. The subhorizontal moderately inclined, at most localities, but steeply dipping quartz–feldspar veins, possible vestiges gneissic layers, core region Ahmic domain. Such planar features could be due shortening strain associated with development 1080 Ma ductile thrusts CGB. domain, on hand, attributable 1020 Ma vertical thinning stack. Transverse gradients total strain, documented others over distances hundreds meters, characterize walls major thrusts. Our results detailed strain-fabric mapping metaplutonic rocks presently situated Ahmic-Parry domain border, apparent sole-thrust segment synformal klippe, provide no evidence for such transverse gradients. We hypothesize original were removed from level present erosion surface, presumably dip-slip extension faulting.