Deformation mechanisms in granodiorite at effective pressures to 100 MPa and temperatures to partial melting

Technical Report · Thu Jan 01 04:00:00 EST 1981

OSTI ID:6851214

Friedman, M; Handin, J; Bauer, S J

Deformation mechanisms in room-dry and water-saturated specimens of Charcoal Granodiorite, shortened at 10/sup -4/s/sup -1/, at effective pressures (Pe) to 100 MPa and temperatures to partial melting (less than or equal to 1050/sup 0/C) are documented with a view toward providing criteria to recognize and characterize the deformation for geological and engienering applications. Above 800/sup 0/C strength decreases dramatically at effective pressures greater than or equal to 50 MPa and water-weakening reduces strength an additional 30 to 40% at Pe = 100 MPa. Strains at failure are only 0.1 to 2.2% with macroscopic ductility (within this range) increasing as the effective pressures are increased and in wet versus dry tests. Shattering (multiple faulting) gives way to faulting along a single zone to failure without macroscopic faulting as ductility increases. Microscopically, cataclasis (extension microfracturing and thermal cracking with rigid-body motions) predominates at all conditions. Dislocation gliding contributes little to the strain. Precursive extension microfractures coalesce to produce the throughgoing faults with gouge zones exhibiting possible Riedel shears. Incipient melting, particularly in wet tests, produces a distinctive texture along feldspar grain boundaries that suggests a grain-boundary-softening effect contributes to the weakening. In addition, it is demonstrated that the presence of water does not lead to more microfractures, but to a reduction in the stresses required to initiate and propagate them.

• Research Organization: Texas A and M Univ., College Station (USA). Center for Tectonophysics
• DOE Contract Number: AS05-79ER10361
• OSTI ID: 6851214
• Report Number(s): DOE/ER/10361-3-3A; CONF-820803-16; ON: DE83003764
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
DATA
DEFORMATION
DUCTILITY
EXPERIMENTAL DATA
FAILURES
FRACTURES
GRANITES
GRANODIORITES
IGNEOUS ROCKS
INFORMATION
MECHANICAL PROPERTIES
MOISTURE
NUMERICAL DATA
PLUTONIC ROCKS
PRESSURE DEPENDENCE
ROCKS
STRAIN RATE
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES