MICROSTRUCTURAL ANALYSIS OF SHEAR ZONES WITHIN THE PENOKEAN OROGEN, MARATHON COUNTY, WISCONSIN

The Penokean orogenic belt is a major early Proterozoic belt that is exposed in north-central Wisconsin. Structural, stratagraphic, and magmatic assemblages of the orogen are typically viewed as the remnants of collision between Archean continental crust to the north (i.e., the Superior Province) and volcanic arc terrane(s) to the south (i.e., the Wisconsin magmatic terrane). Although the Penokean orogen has long been studied, little is known about the kinematics of deformation within the Wisconsin magmatic terrane. This study focuses on a structural analysis of shear zones exposed in the Wausau magmatic terrane. Specifically, we have collected oriented samples from four shear zones in Marathon County, Wisconsin. Shear sense indicators within these zones include: sigma- and delta-type mantled porphroclasts, strain shadows, microfaults, S/C fabrics, mica fish and oblique grain fabrics. This presentation will focus on presenting this data in the context of regional kinematic models for the orogen.