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JJK Thesis(5-11-21).pdf (19.47 MB)

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EFFECT OF PRE-EXISTING HETEROGENEITIES ON STRAIN LOCALIZATION IN A FOLIATED GRANITIC GNEISS

Kullberg, Jonathan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1621600334762676

Abstract Details

2021, Master of Science, University of Akron, Geology.
While Earth’s crust is often modelled as a homogenous material, heterogeneities such as foliations, lattice preferred orientations (LPOs), and pre-existing brittle deformations are common and may affect the strength of the crust. To investigate the effects of pre-existing heterogeneities on crust strength, axial compression experiments were performed on pre-faulted samples of a fine-grained (d = 150μm) gneiss (Gneiss Minuti) with a granitic composition consisting of plagioclase (53%), quartz (29%), potassium feldspar (10%), biotite (7%) and accessory garnet/Fe-Ti oxides (1%). Cores with varied orientations of foliation and lineation to the compression direction were deformed in a Griggs-type piston rock deformation apparatus in order to determine if these heterogeneities would affect the strength or localization in a pre-existing fault. An initial brittle fault that cross-cuts the foliation was formed in all samples at low confining pressure (Pc = 50 – 250 MPa) and temperatures (T = ~25°C). Samples were then brought to final conditions, Pc = 1500 MPa, T = 700°C, and deformed at a constant axial strain rate of ~2 x 10-7 s-1. At final conditions, the fine-grained fault gouge of the brittle fault was annealed and subsequently deformed by diffusion-accommodated grain boundary sliding within the shear zone, regardless of foliation orientation. Strain remained localized along the shear zone until strains of at least ~12 - 15%, and the strain rate of the low to mid strain samples within the shear zone was calculated to be ~10-5 s-1. In a sample deformed to higher strain (44%) the surrounding rock began to deform via dislocation creep. The results of this study suggest that strain localization will most likely be controlled by a preexisting fault, regardless of the orientation of the foliation in the surrounding host rock.
Caleb Holyoke, (Advisor)
John Peck, (Committee Member)
David Steer, (Committee Member)
Geology
viscous; anisotropy; pre-existing heterogeneities; foliation; gneiss

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Citations

  • Kullberg, J. (2021). EFFECT OF PRE-EXISTING HETEROGENEITIES ON STRAIN LOCALIZATION IN A FOLIATED GRANITIC GNEISS [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1621600334762676

    APA Style (7th edition)

  • Kullberg, Jonathan. EFFECT OF PRE-EXISTING HETEROGENEITIES ON STRAIN LOCALIZATION IN A FOLIATED GRANITIC GNEISS. 2021. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1621600334762676.

    MLA Style (8th edition)

  • Kullberg, Jonathan. "EFFECT OF PRE-EXISTING HETEROGENEITIES ON STRAIN LOCALIZATION IN A FOLIATED GRANITIC GNEISS." Master's thesis, University of Akron, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1621600334762676

    Chicago Manual of Style (17th edition)

akron1621600334762676
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