Some petrophysical properties of the predominant rocks from the Archaean section of the Kola superdeep borehole SG-3

Автор: Trishina O.M., Gorbatsevich F.F., Kovalevskiy M.V.

Журнал: Вестник геонаук @vestnik-geo

Рубрика: Научные статьи

Статья в выпуске: 10 (274), 2017 года.

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The values of density and velocity in the samples of the predominant rocks from the Archaean section of the Kola superdeep borehole (SG-3), drilled in the northern frame of the Pechenga palaeorift structure, were studied. The main part of rocks of the SG-3 Archaean section is represented by gneisses, schists and amphibolites. Their main rock forming minerals are plagioclase, hornblende, mica and quartz. The structure of the rocks is mainly medium-grained, the texture is nematogranoblastic and lepidogranoblastic. The elastic anisotropy and orientation of the rock texture were estimated by the acoustopolariscopy method, the density and velocity of compression and shear waves were determined in the laboratory and the mentioned characteristics were calculated by mineral composition. The measured sample velocities are unusually low, which can be explained by the decompaction effect of deep rocks. The values of the velocity characteristics that are close to those for the conditions of the rock deep occurrence are obtained by calculation with regard to their specific mineral composition. The average values of the velocity of compression and shear waves for gneisses calculated by mineral composition are 6.38 ± 0.16 km/s and 3.52 ± 0.14 km/s, respectively. The average of the compression wave velocity for schists is 6.40 ± 0.13 km/s, of the shear wave velocity - 3.46 ± 0.09 km/s, and for amphibolites 6.84 ± 0.13 km/s and 3.82 ± 0.08 km/s, respectively. The ratios of the values of compression and shear moduli in different rocks exhibit the same trends as the average velocities. However, their values are lower in schists, medium in gneisses and grater in amphibolites.

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Kola superdeep borehole (sg-3), deep rocks, properties, densities, compression and shear wave velocities

Короткий адрес: https://sciup.org/149129230

IDR: 149129230   |   DOI: 10.19110/2221-1381-2017-10-31-41

Статья научная