Date of Award
Dr. Dexter Perkins
Granulite facies metamorphism is reported to have occurred in the Granite Falls-Montivideo area of the Minnesota River Valley and a broader view of the valley is taken to determine the extent of granulite facies metamorphism. Pressures and temperatures of metamorphism were determined using two geothermometers and one geobarometer. Based upon two-feldspar and garnet-biotite thermometers, temperature of metamorphism is approximated at 600 °c. Metamorphic pressures based on the reaction cordierite= garnet+ quartz + sillimanite were probably between 4 and 6 Kbars. Based on barometry and thermometry, it is suggested the Algoman o rogeny (2600 m.y. ago) was at least upper amphibolite and probably marginal to granulite facies, while the basement complexes have undergone granulite facies metamorphism.
Leier, Paula J., "Thermometry And Barometry Of Precambrian Orthogneisses And Related Rocks From The Minnesota River Valley, Southwestern Minnesota" (1982). Undergraduate Theses and Senior Projects. 132.