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Archean Metamorphosed Ultramafic Rocks And Chromitites From The Beartooth Mountains, Montana, Usa: Insights Into Mantle Geochemistry And Tectonics, Rachel M. Gnieski

LSU Master's Theses

Metamorphosed ultramafic rocks and associated chromitite pods in the eastern Beartooth Mountains, Montana (USA) provide a window into the tectonic evolution of the Archean northern Wyoming Province. Meta-ultramafic rocks occur with a variety of metasupracrustal rocks as xenoliths in an extensive 2.8 Ga suite of TTG (meta)plutonic rocks. The origin of the ultramafic rocks is obscured by an upper amphibolite-to-greenschist facies overprint. Major element analyses (XRF, wt. %) of meta-ultramafic host rocks show SiO₂ from 40.53-50.37, MgO from 15.33-45.25, TiO₂ from 0.07-0.62, Al₂O₃ from 1.25-10.62, and Fe₂O₃(t) from 8.06-14.54. Total alkali …