Inferring the Thermomechanical State of the Lithosphere Using Geophysical and Geochemical Observables
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shinevar-shinevar-phd-eaps-2021-thesis.pdf
Description
Thesis PDF
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12.06 MB
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Adobe PDF
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eed7ff072be8a47dfba97d1e80b33667
Author(s)
Shinevar, William Joseph
Advisor(s)
Jagoutz, Oliver
Behn, Mark D.
Date Issued
September 2021
Publisher
Massachusetts Institute of Technology
Abstract
This thesis focuses on interpreting geophysical and geochemical observables in terms of the thermomechanical state of the lithosphere. In Chapter 1, I correlate lower crustal rheology with seismic wave speed. Compositional variation is required to explain half of the total variability in predicted lower crustal stress, implying that constraining regional lithology is important for lower crustal geodynamics. In Chapter 2, I utilize thermobarometry, diffusion models, and thermodynamic modelling to constrain the ultra-high formation conditions and cooling rates of the Gore Mountain Garnet Amphibolite in order to understand the rheology of the lower crust during orogenic collapse. In Chapter 3, I interpret geophysical data along a 74 Myr transect in the Atlantic to the temporal variability and relationship of crustal thickness and normal faults. In Chapter 4, I constrain the error present in the forward-calculation of seismic wave speed from ultramafic bulk composition. I also present a database and toolbox to interpret seismic wave speeds in terms of temperature and composition. Finally, in Chapter 5 I apply the methodology from Chapter 4 to interpret a new seismic tomographic model in terms of temperature, density, and composition in order to show that the shallow lithospheric roots are density unstable.
MIT Department
Joint Program in Marine Geology and Geophysics
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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