Emplacement and deformation of granites during transpression: magnetic fabrics of the Archean Sparrow pluton, Slave Province, Canada

The Sparrow pluton is part of the Prosperous Suite of two-mica granites that crop out within amphibolite grade meta-greywackes of the southern Yellowknife Domain, in the Slave Province of the Canadian Shield. The magnetic susceptibility (K) and the anisotropy of magnetic susceptibility (AMS) were used to systematically map the structural patterns in the pluton and to establish the relationship between plutonism and Late Archean tectonics in the region. Paramagnetic Fe-phyllosilicates (biotite, chlorite) and very fine-grained magnetite contribute to K and to the AMS. The magnetic foliation and the magnetic lineation are predominantly controlled by the biotite fabrics and their orientations are consistent with the regional D2 strain field. The horizontal magnetic lineations in the Sparrow pluton suggest a horizontal stretching component associated with the regional D2 event. The zonation defined by K values is compatible with a fold pattern trending parallel to the regional F2 folds and S2 foliation and to the magnetic fabric trends in the pluton. The intensities and symmetries of the AMS also define map patterns that are consistent with D2 deformation. Microstructural study indicates the pluton recorded D2 strain as it crystallized and cooled from the solidus, demonstrating syn-D2 emplacement. The results indicate the pervasive structural patterns in the Sparrow pluton are an integral part of the regional strain field, and that they are kinematically consistent with a transpressive D2 strain regime. Mapping the fabric patterns within syntectonic plutons provides a useful approach to the kinematic analysis of synemplacement deformation events in multiply deformed metamorphic terranes.