Acta Geodynamica et Geomaterialia

Title: COMPARISON OF PETROPHYSICAL PROPERTIES OF PREDOMINANT ROCKS FROM THE ACHAEAN SECTION OF THE KOLA SUPERDEEP (SG-3)
Authors: Trishina Olga, Gorbatsevich Feliks and Kovalevskiy Mikhail
DOI: 10.13168/AGG.2018.0018
Journal: Acta Geodynamica et Geomaterialia, Vol. 15, No. 3 (191), Prague 2018
Full Text: PDF file (2.5 MB)
Keywords: Kola superdeep borehole (SG-3), Archaean deep rocks, properties, densities, compression and shear wave velocities
Abstract: 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 have been 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 texture of the rocks is mainly medium-grained, the structure is nematogranoblastic and lepidogranoblastic. The parameters of elastic anisotropy were estimated by the acoustopolariscopy method, the density and velocity of compression and shear waves were determined in the lab 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 were obtained by calculation with regard to their specific mineral composition. The average values of the velocity of compression and shear waves for gneisses were 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 dynamic moduli in different rocks are lower in schists, medium in gneisses and higher in amphibolites.