V. L. Il’chenko*, F. F. Gorbatsevich*, and Yu. P. Smirnov**
* Geological Institute, Kola Research Center, Russian Academy of Sciences, ul. Fersmana 14,
Murmansk oblast, Apatity, 184200 Russia
** NPTs Kolskaya Sverkhglubokaya, Russia
Received April 1, 1998
Abstract—By means of acoustic polarization, core samples obtained from the Kola super-deep borehole at a
depth of 8.7–11.4 km were studied. The analysis of the data obtained and their comparison with the data of
model experiments show that, as a results of repeated tectonic actions, superposition of several non-compen-
sated paleostress fields different in their direction and duration of action, and the high non-uniformity of dimen-
sional orientation of elements of elastic symmetry of rocks throughout the geological section and decrease in
their strength became apparent, promoting considerable improvement in rock drillability.