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Thesis
Garnet reaction mechanisms in polymetamorphic rocks from central Maine
University of Iowa
Master of Science (MS), University of Iowa
Autumn 2001
DOI: 10.25820/etd.007300
Abstract
The polymetamorphic terrane in west central Maine is an ideal place to investigate reaction mechanisms involving garnet because the garnet has undergone multiple growth and dissolution phases. This study examines the origin of the complex zoning patterns and relates them to the P-T history of the area.
The rocks have gone at least three separate periods of metamorphism (M1, M2 and M3). M1 is a regional greenschist event between 418 and 405 Ma.
M2 is a staurolite + garnet + biotite +/- andalusite bearing assemblage with an age of approximately 405 Ma and is responsible for the initial garnet growth. Cooling after M2 produced the high grossular ring observed in most garnets. The pressure increase between M2 and M3 was responsible for growing the high Ca ring.
M3 heating is responsible for dissolving garnet due to staurolite forming reactions, growing garnet because of staurolite dissolving at higher temperatures or dissolving garnet due to the growth of sillimanite. It is comprised of three events. M3a resulted from the intrusion of Phillips pluton at approximately 403 Ma. M3b resulted from the older pulse of the Mooselookmeguntic complex approximately 390 Ma and M3c resulted from the younger pulse of the Mooselookmeguntic complex approximately 370 Ma.
Gibbs modeling indicates M2 metamorphism resulted from increasing P and T from 480oC at 1.4 kbars to maximum temperatures between 554oC and 560oC at 3.0 kbars, not isobaric heating at 3.0 kbars. Modeling of the M3 zoning patterns and textures suggests M3 metamorphism was caused by isobaric heating to maximum temperatures of 561°C to 575°C at 3.5 kbars.
Details
- Title: Subtitle
- Garnet reaction mechanisms in polymetamorphic rocks from central Maine
- Creators
- Matthew James Burreson
- Contributors
- C T Foster (Advisor) - University of Iowa, Earth and Environmental SciencesJane A Gilotti (Committee Member) - University of Iowa, Earth and Environmental SciencesMark Reagan (Committee Member) - University of Iowa, Earth and Environmental Sciences
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Geoscience
- Date degree season
- Autumn 2001
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007300
- Number of pages
- x, 97 pages
- Copyright
- Copyright © 2001 Matthew James Burreson. Posted by permission of the author.
- Grant note
- Funding for the research was provided by the National Science Foundation grant EAR 9814372 to C. T. Foster.
- Language
- English
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984632258002771
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