Joint South-Central and North-Central Sections, both conducting their 41st Annual Meeting (11–13 April 2007)

Paper No. 26
Presentation Time: 1:40 PM-5:00 PM

MINERALOGY AND CHEMISTRY OF MOUNTAIN SHEAR ZONE OF NORTHERN WISCONSIN


ADAMS, Kristin M., Geography and Geology, University of Wisconsin-Whitewater, Department of Geography and Geology, Upham Hall 120, Whitewater, WI 53190, ASLESEN, Andrew D. and BHATTACHARYYA, Prajukti, Geography and Geology, University of Wisconsin - Whitewater, 120 Upham Hall, 800 Main Street, Whitewater, WI 53190, adamskm17@uww.edu

Ductile shear zones are formed when rocks change without breaking, and the causes behind shear zone formation are currently not completely understood. Our study focuses on the reasons behind the shear zone formation in Mountain, Wisconsin, located in Oconto County. The shear zone we studied was formed during the Proterozoic Penokean orogeny, and consists of granitic gneiss which has been locally intruded by basaltic dikes. The shear zone of Mountain, Wisconsin, is unique because while most of the other deformation sites in Wisconsin are covered with glacial deposition, this one is well exposed. Specimens from three different locations within the study area were collected. For samples containing small scale (several centimeters in width) shear zones, the mineralogy and chemistry of the deformed and relatively undeformed areas within the same hand sample were compared using a petrographic microscope and x-ray diffraction machine (XRD). The specimens with small dikes (centimeters in scale) that may have intruded within the shear zones were also mineralogically and chemically studied and compared with data from sheared samples to determine whether mineralogical or chemical heterogeneity due to the dike intrusion had any effect on deformation.