Strain and folding mechanisms in a similar style fold from the northern Selkirks of the Canadian Cordillera

摘要: Abstract Minor structures and intragranular strain in calcite have been examined a folded marble unit near Mica Dam, 130 km north of Revelstoke, British Columbia. The fold forms part train polyclinal folds the core major Dam Antiform which formed third folding phase, F 3 Metamorphism had reached kyanite grade before , biotite quartz were recrystallizing early but no longer did so later stages. Pressure 4.0–5.0 kbar temperatures 300–400°C are estimated to prevailed during folding. is an asymmetric, approximately cylindrical antiform with axial surface dipping southwest hinge plunging southeast at 12°. parameters t ′ α T determined on right section indicate be similar. Calc-silicate layers pegmatite sheets outline both buckled boudine adjacent synform limited by upper detachment surface. Other minor folds, related Antiform, exhibit same characteristics all this indicates that there was buckle component history. Using least-squares strain-gage technique, twinning strains for five samples marble. maximum extensional strain, ϵ subparallel layering high angle hinge. All compression nearly parallel These do not reflect buckling mechanism suggested field observations. late-stage three-dimensional observed compatible existing two-dimensional, theoretical models origin similar style folds.