Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 2 of 2
Full-Text Articles in Geology
Proterozoic Metamorphism Of The Tobacco Root Mountains, Montana, John T. Cheney, John B. Brady, Kara A. Tierney, Kathleen A. Degraff, Heidi K. Mohlman, Jessica D. Frisch, Christine E. Hatch, Michael L. Steiner, Sarah K. Carmichael, Robin G.M. Fisher, Carrie B. Tuit, Kurt J. Steffen, Pamela Cady, Josh Lowell, Leandra L. Archuleta, Jillian Hirst, Karl W. Wegmann, Brian Monteleone
Proterozoic Metamorphism Of The Tobacco Root Mountains, Montana, John T. Cheney, John B. Brady, Kara A. Tierney, Kathleen A. Degraff, Heidi K. Mohlman, Jessica D. Frisch, Christine E. Hatch, Michael L. Steiner, Sarah K. Carmichael, Robin G.M. Fisher, Carrie B. Tuit, Kurt J. Steffen, Pamela Cady, Josh Lowell, Leandra L. Archuleta, Jillian Hirst, Karl W. Wegmann, Brian Monteleone
Geosciences: Faculty Publications
Textures and mineral assemblages of metamorphic rocks of the Tobacco Root Mountains are consistent with metamorphism of all rocks during the Big Sky orogeny (1.77 Ga) at relatively high pressure (P >1.0 GPa) followed by differential reequilibration on a clockwise P-T path at lower pressures (0.6–0.8 GPa). The highest pressures are documented by coarse-grained kyanite and orthopyroxene in aluminous orthoamphibolites, which require P ≥ 1.0 GPa. Other higher-pressure mineral assemblages of note include kyanite + orthoamphibole and kyanite + K-feldspar. Abundant textural evidence for partial melting in pelitic and basaltic rocks includes leucosomes, very large (several cm across) porphyroblasts of …
Advances In The Geology Of The Tobacco Root Mountains, Montana, And Their Implications For The History Of The Northern Wyoming Province, Tekla A. Harms, John B. Brady, H. Robert Burger, John T. Cheney
Advances In The Geology Of The Tobacco Root Mountains, Montana, And Their Implications For The History Of The Northern Wyoming Province, Tekla A. Harms, John B. Brady, H. Robert Burger, John T. Cheney
Geosciences: Faculty Publications
Integrated studies by Keck Geology Consortium participants have generated many new insights into the Precambrian geology of the Tobacco Root Mountains. We have clarified the tectonic setting and origin of two suites of metamorphic rocks: (1) a quartzofeldspathic gneiss complex with associated metasupracrustal rocks (the combined Indian Creek and Pony–Middle Mountain Metamorphic Suites) that originated in a continental arc setting between 3.35 and 3.2 Ga with subsequent sedimentation and (2) mafic metavolcanic rocks with intercalated metasedimentary rocks (the Spuhler Peak Metamorphic Suite) from a suprasubduction zone ophiolite or backarc basin possibly of Proterozoic age. A poorly preserved metamorphic event at …