Influence of the state of stress on the brittle-ductile transition in granitic rock: Evidence from fault steps in the Sierra Nevada, California

Journal Article · Wed Jul 01 04:00:00 EDT 1992 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1992)020<0645:IOTSOS>2.3.CO;2· OSTI ID:7004342

Buergmann, R; Pollard, D D ^[1]

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1. Stanford Univ., CA (United States)

Left-lateral strike-slip faults in the Lake Edison granodiorite (central Sierra Nevada, California) are composed of an echelon segments. Relative displacement across the faults apparently are transferred between segments by ductile shearing at right steps, and by extensional fracturing at left steps. The granodiorite within right steps displays mylonitic foliation, and thin sections show textures in quartz associated with dislocation glide, recovery processes, and dynamic recrystallization, whereas textures in feldspar are related to fracturing. Only centimeters outside the right steps, the rock fabric is approximately isotropic and deformation is accommodated by mineralized opening-mode fractures. The stress field calculated for the right-step geometry, when a boundary element model is used, shows an increase in mean compressive stress of up to 25 MPa within the step relative to that outside. This difference in stress apparently produced the contrasting behaviors of the granitic rock. Experimentally derived power-law flow laws do not predict these behaviors.

• OSTI ID: 7004342
• Journal Information: Geology; (United States), Journal Name: Geology; (United States) Vol. 20:7; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
DEFORMATION
DEVELOPED COUNTRIES
DUCTILE-BRITTLE TRANSITIONS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GRANITES
GRANODIORITES
IGNEOUS ROCKS
MECHANICAL PROPERTIES
MECHANICS
NORTH AMERICA
PLUTONIC ROCKS
ROCK MECHANICS
ROCKS
STRESS ANALYSIS
USA