Elastic properties of granulite facies rocks of Mahabalipuram, Tamil Nadu, India |
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| Authors: | M V M S Rao K J Prasanna Lakshmi L P Sarma K B Chary |
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| Institution: | (1) National Geophysical Research Institute, 500 007 Hyderabad, India |
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| Abstract: | Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples
of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient
conditions using ‘time-of-flight’ pulse transmission technique at 1.0 MHz frequency. The results show linear relationships
between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities
and higher attenuation than the intermediate and basic granulites. The average values of the Poisson’s ratio of acidic, intermediate
and basic granulites have been found to be 0.210, 0.241 and 0.279 respectively. The variations in velocities and attenuation
in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity
data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding
studies indicate that these granulite facies rocks may belong to mid-crustal depths only. |
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| Keywords: | Velocities Poisson’ s ratio attenuation granulite facies rocks |
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