Deformation of Fine-Grained Quartz Aggregates by Mixed Diffusion and Dislocation Creep

abstract

• 2018. American Geophysical Union. All Rights Reserved. Hot-pressed polycrystalline quartz samples with grain sizes of 1.712.0m and water contents of 3,500ppm H/Si were deformed in a solid-pressure-medium (Griggs-type) deformation apparatus at temperatures of 600 to 950C, confining pressures of 0.9 to 1.5GPa and strain rates of 103.3 to 105.9/s. Two different flow regimes are distinguished at low and high temperatures. The stress exponent determined at low temperatures (600750C) increased from 2.9 to 5.2 with an activation energy of 12933kJ/mol, consistent with previous quartz dislocation creep laws indicating operation of dislocation creep. In contrast, the stress exponent determined at high temperatures (800950C) is 1.70.2 with an activation energy of 18325kJ/mol. A fugacity exponent determined at 800C was 1.00.2. All samples show evidence of basal slip. However, flow strengths at high temperatures also depend on grain size with a small grain size exponent of 0.510.13. Mechanical, microstructural, and textural results suggest that deformation occurs by a combination of intracrystalline and grain boundary processes. The flow law determined from the high-temperature data can be fit by (Formula presented.) with stress, in MPa, grain size, d in m, (Formula presented.) in MPa, and Tk in Kelvin. At conditions of the middle crust and tectonic strain rates, deformation depends on grain size where the strength is weaker than for pure dislocation creep even for grain sizes >10m.

• Kronenberg, Andreas

published proceedings

• JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH

author list (cited authors)

• Fukuda, J., Holyoke, C., & Kronenberg, A. K.

citation count

• 19

complete list of authors

• Fukuda, Jun-ichi||Holyoke, Caleb WIII||Kronenberg, Andreas K

publication date

• June 2018

publisher

• American Geophysical Union (AGU)  Publisher

published in

• Journal of Geophysical Research (JGR): Solid Earth  Journal

keywords

• Crustal Strength
• Grain Size Dependence
• Quartz Flow Law
• Stress Dependence

Digital Object Identifier (DOI)

• 10.1029/2017JB015133

start page

• 4676

end page

• 4696

volume

• 123

issue

• 6

URL

• http://dx.doi.org/10.1029/2017jb015133