20 Micro to Macro: Linking Structural Geology, Petrology, Geochronology, and Tectonics Across Scales

Monday, 18 March 2024
8:00 AM - 12:00 PM
Piscataquog Room

APPLICATION AND EXPLORATION OF THE PERIMETER-AREA FRACTAL DIMENSION OF RECRYSTALLIZED QUARTZ GRAIN BOUNDARIES: A CASE STUDY FROM THE SANDHILL CORNER SHEAR ZONE

Paper number: 20-8
Program: Theme Sessions
Time: 10:00 AM – 10:20 AM

Authors

Abstract

The microstructure of polycrystalline rocks strongly influences their mechanical properties. In metals, the characterization of dynamically recrystallized grains through fractal analysis has demonstrated relationships between the perimeter-area fractal dimension (D-value), deformation conditions (i.e., strain-rate and temperature), and physical properties such as creep rupture strength. Deformation experiments on monocrystalline quartz aggregates suggest a similar relationship between the D-value and strain rate. To explore the utility of the perimeter-area fractal dimension as a strain rate meter, we apply it to deformed and recrystallized quartz veins across the seismogenic Sandhill Corner shear zone, a well-documented mid-crustal dextral transpressive shear zone exhumed from the base of the frictional to viscous transition zone. The spatial pattern and range of strain rate estimates from D-values is remarkably similar to that of 9 published flow laws. Additional comparisons of the D-value with common measurements of shape properties (e.g., RMS grain size, aspect ratio, circularity, roundness) demonstrate an interdependence on aspect ratio and grain boundary irregularity, and a strong negative correlation with RMS grain size, suggesting its potential use as a flow-stress piezometer. Theoretical considerations and preliminary modeling also suggest the D-value contains information on deformation mechanisms during dynamic recrystallization. Future experimental work is required to constrain and verify these relationships.

Geological Society of America Abstracts with Programs. Vol. 56, No. 1

doi: 10.1130/abs/2024NE-397280

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