Publication Date
2025
Document Type
Dissertation/Thesis
First Advisor
Autrey, Suzanne R.
Degree Name
M.S. (Master of Science)
Legacy Department
Department of Geology and Environmental Geosciences
Abstract
Local occurrences of andalusite and kyanite in Echo Canyon, within the Funeral Mountains metamorphic corecomplex, overprint chlorite-grade phyllites and reveal the presence of a hidden pluton and its contact aureole. Phase equilibria models indicate minimum conditions of 0.45 GPa and 535 °C in the highest-grade zone of the aureole, with significantly higher temperatures than previously estimated for the area. This study applied phase equilibria pressure-temperature modeling, petrography, Raman spectroscopy, and ⁴⁰Ar/³⁹Ar geochronology on muscovite to characterize this anomalous metamorphism and to place it within a revised tectonic framework. Two potentially coeval prograde metamorphic events have been recognized based on petrographic textural analysis: M1 and M2. M1 was a phyllite- grade metamorphic event that led to the development of a primary tectonic foliation (S1) comprised of mica, quartz, and chlorite. M2 was identified as a contact metamorphic event associated with prograde chloritoid, andalusite, and kyanite. Previous models for the Funeral Mountains attributed Late Jurassic prograde metamorphism to retro-arc underthrusting during early Sevier orogenesis, which was followed by a period of Jurassic decompression and cooling. New ⁴⁰Ar/³⁹Ar muscovite partial plateau ages range from 156 to 165 Ma, suggesting that contact metamorphism was coeval with either Jurassic thrust burial or Jurassic exhumation that occurred in the Funeral Mountains. Chlorite-grade phyllites in the field area likely formed during this Jurassic prograde metamorphism (M1). In the local region of Echo Canyon, contact metamorphism (M2) occurred. Newly mapped mineral isograds show the change from chloritoid to andalusite and then to kyanite-bearing assemblages occurring over < 0.5 km, suggesting that a pluton is present at depth below Echo Canyon.
Recommended Citation
Montañez, Keanu, "Constraining the Timing and Degree of Metamorphism in the Echo Canyon Region: Evidence for a Cryptic Contact Aureole" (2025). Graduate Research Theses & Dissertations. 8168.
https://huskiecommons.lib.niu.edu/allgraduate-thesesdissertations/8168
Extent
179 pages
Language
en
Publisher
Northern Illinois University
Rights Statement
In Copyright
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.
Media Type
Text
