Kinematic analysis of the Kynsikangas Shear Zone, SW-Finland

Similar to many Paleoproterozoic orogens, the Svecofennian in SW-Finland is characterized by a network of prominent ductile shear zones, often lining granitoid pluton boundaries. Knowledge of the deformation kinematics of the shear zones helps elucidating the tectonic evolution of, and possible role of lower crustal deformation in pluton emplacement in, the Svecofennian Orogen. In cooperation with the Geological Survey of Finland (GTK), we explore the kinematics of the Kynsikangas Shear Zone in the Kokemäki area. Here, this shear zone is made up of metagranitoid and migmatite lining the eastern border of a Rapakivi pluton. The metagranitoid rocks lend themselves excellently for a detailed structural study of the Kynsikangas Shear Zone. The field-based study includes the analysis of metamorphic mineral shape fabrics in terms of orientation, geometry, intensity and microstructure. In addition to the mentioned objectives, systematic mapping of asymmetric mineral fabrics, such as outcrop-scale foliation boudinage and smaller-scale rolling structures, is expected to shed light on an important controversy among structural geologists, i.e., whether small-scale kinematic indicators can adequately portray the overall kinematics of kilometer-scale shear zones.

 

Funding Agency: The Geological Survey of Finland (GTK)

 

Principal Investigator: Ulrich Riller

 

External collaborators:

- Jon Engström (GTK Finland at Espoo)