Paleoremanence dispersal across a transpressed Archean terrain: Deflection by anisotropy or by late compression?

The Quetico Belt is an Archean metasedimentary terrain sandwiched between greenstone subprovinces. A single regional schistosity is subparallel to magnetic foliation defined by anisotropy of low‐field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanence (AARM). Aligned micas are the primary cause of AMS. Aligned pyrrhotite is the sole cause of AARM. Each magnetic subfabric is due to minerals that grew in overlapping intervals in the strain history. Their slight obliquity may be due to crystallization during noncoaxial strain. Magnetic fabric ellipsoids suggest varying severity of flattening: very strong flattening on the northern boundary, less severe on the southern boundary, and least severe in the interior. The interior and the southern boundary of the belt stretched horizontally and the shortening direction varies gradually, from NS in the north to NNW in the south. The paleomagnetic record carried by pyrrhotite shows characteristic remanences dispersed around a great circle subparallel to the regional schistosity and magnetic foliations. Late stress effects rotated paleoremanences into this pattern; we discount deflection of the paleofield by anisotropy. The pattern of dispersal indicates uniaxial oblate flattening of the region with NNW‐SSE shortening, late in the metamorphic cooling history (<300°C). This postdates schistosity, AMS and AARM fabrics but it is controlled by the same kinematic pattern.