Magnetic fabrics and anisotropy-controlled thrusting in the Kapuskasing Structural Zone, Canada

摘要: Abstract Magnetic fabrics of upthrust Archean lower crustal rocks in the Kapuskasing Structural Zone (KSZ), northern Ontario, reveal previously unrecognized, consistently oriented mineral orientation–distributions. These define a schistosity and extension lineation that cuts across heterogeneously strained contorted gneissic layering. The cryptic, magnetically determined is subparallel to diffuse but seismic reflectors granulite upper amphibolite facies gneisses. reflections were unexplained because their consistent orientation did not conform lithological layering we can now attribute them preferred orientations instead. magnetic lies within plane reflectors. bounding thrust fault postdates recorded by anisotropy low-field susceptibility (AMS) are primarily dictated subtle distribution silicate minerals magnetite inclusions. Anisotropy anhysteretic remanence (AARM) isolates component fabric due magnetite. This differs slightly from `whole-rock' AMS signature susceptible late recrystallization or domain-rearrangement changes its response later phases noncoaxial stress history. Both AARM lineations subhorizontal, trending 075° 060°, respectively. incompatible with uplift kinematics must reflect ancient direction at depth. However, similarity trends strike suggest boundary propagated upwards foliation using path least resistance afforded lineation.