The rocks of the Beartooth Mountains of Montana and Wyoming span 4 billion years of earth history. The geologic features range from the more recent spectacular glaciation of the Beartooth Plateau and the volcanism and thermal activity of the Yellowstone area (south of the Beartooth Mountains) to the ancient crust containing constituents that are over 4 billion years old.
The ancient rocks and minerals in the Beartooth Mountains are part of one of oldest pieces of crust in North America and provide many insights into early crustal formation on the Earth.
The LSU Department of Geology and Geophysics has had a presence in this terrane for a number of years. Darrell Henry, his students and colleagues from Montana State University and University of Florida have been engaged in investigations of the petrology and geochemistry of the ancient rocks (more than 2.8 billion years) that form most of the Beartooth Mtns. Most of the eastern portion of the Beartooth Mtns are composed of granitic rocks with large xenoliths of older metamorphosed sedimentary and igneous rocks that were tectonically interleaved on a meter-scale. The major thrust of the research has involved establishment of the conditions of metamorphism and the tectonic processes the operated prior to 2.8 billion years ago. The complex tectonic mixing of the xenoliths results in unique challenges that require novel approaches. For instance, Andy Maas (current LSU MS student) has used cathodoluminescene of sillimanite to establish the reactions that took place upon crystallization of a former melt.
