Strain analysis of Archean rocks from the Virginia Horn area, NE Minnesota

The Virginia Horn refers to the structure where the outcrop pattern of the Biwabik Iron Formation makes a sharp bend southward and then back north as a part of a broad, gently plunging anticlinal and synclinal flexure, near the city of Virginia in northeastern Minnesota, exposing supracrustal rocks of Archean age within the core of the anticline. Three deformation events have affected these rocks (Jirsa and Boerboom 2003). Strain analysis on three graywacke samples from the area was performed in order to determine whether the small-scale structures present in the rocks are consistent with the megascopic structure. Specifically, the Rf/Ф phi method proved to be reliable and consistent when applied to these samples. The strain data show that graywackes from the area exhibit a degree of flattening consistent with the D2 deformation. Acknowledgements I would like to thank Jim Welsh for his assistance and advisement throughout this project. Also Laura Triplett and Alan Gishlick for their help with writing this thesis. And Alan again for all his technological help throughout the year. Table of