Fabric-related velocity anisotropy and shear wave splitting in rocks from the Santa Rosa Mylonite Zone, California
Conference
·
· Journal of Geophysical Research; (United States)
OSTI ID:5446677
- Mineralogisch-Petrographisches Institut Universitaet Kiel (West Germany)
- Univ. of California, Berkeley (USA)
The directional dependence of P and S wave velocities have been measured at pressures (up to 600 MPa) and temperatures (up to 700C) in rocks from the Santa Rosa Mylonite Zone (southern California). During tectonism, these were progressively deformed from granodiorite protolith to mylonite and ultimately phyllonite. The mineralogical and chemical composition of protolith and mylonite is nearly identical. Thus these rocks provide excellent material for documenting the effect of microstructural and textural changes on rock anisotropy. Velocity anisotropy increases significantly with the degree of deformation, whereas average velocities and densities do not change. At low pressure (50 MPa) the velocity anisotropy ranges from 1.7% in granodiorite up to 19% in phyllonite and is due to both oriented microfractures and crystallographic preferred orientation. At high pressure (600 MPa), the residual anisotropy up to 12% is mainly due to preferred mineral orientation, in particular of biotite. Significant shear wave splitting is measured parallel to the foliation plane and shows a good correlation with the biotite texture. These observations confirm that oriented microcracks and preferred orientation of minerals should be taken into account in the interpretation of seismic reflection and refraction data in terranes with deformed rocks.
- OSTI ID:
- 5446677
- Report Number(s):
- CONF-880531--
- Conference Information:
- Journal Name: Journal of Geophysical Research; (United States) Journal Volume: 95:B7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
580000* -- Geosciences
ANISOTROPY
BIOTITE
BIREFRINGENCE
CALIFORNIA
CHEMISTRY
CRYSTAL STRUCTURE
DATA ANALYSIS
DEFORMATION
DEVELOPED COUNTRIES
FEDERAL REGION IX
GEOCHEMISTRY
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOPHYSICAL SURVEYS
MICA
MICROSTRUCTURE
MINERALOGY
MINERALS
NORTH AMERICA
ORIENTATION
PRESSURE DEPENDENCE
REFRACTION
RESERVOIR PRESSURE
RESERVOIR ROCK
RESERVOIR TEMPERATURE
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC SURVEYS
SEISMIC WAVES
SILICATE MINERALS
SURVEYS
TECTONICS
TEMPERATURE DEPENDENCE
TEXTURE
USA
WAVE PROPAGATION
580000* -- Geosciences
ANISOTROPY
BIOTITE
BIREFRINGENCE
CALIFORNIA
CHEMISTRY
CRYSTAL STRUCTURE
DATA ANALYSIS
DEFORMATION
DEVELOPED COUNTRIES
FEDERAL REGION IX
GEOCHEMISTRY
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOPHYSICAL SURVEYS
MICA
MICROSTRUCTURE
MINERALOGY
MINERALS
NORTH AMERICA
ORIENTATION
PRESSURE DEPENDENCE
REFRACTION
RESERVOIR PRESSURE
RESERVOIR ROCK
RESERVOIR TEMPERATURE
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC SURVEYS
SEISMIC WAVES
SILICATE MINERALS
SURVEYS
TECTONICS
TEMPERATURE DEPENDENCE
TEXTURE
USA
WAVE PROPAGATION