STRESSANDSTRAIN RECONSTRUCTION FOR THE EASTERN SEGMENT OF THE BALTIC SHIELD

• Published in: Geodynamics & Tectonophysics
• Main Authors: Lidia A. Sim, Dmitry V. Zhirov, Anton V. Marinin, Лидия Андреевна Сим, Дмитрий Вадимович Жиров, Антон Витальевич Маринин
• Other Authors: РФФИ, А.А. Козырев, В.В. Рыбин (Горный институт Кольского научного центра), Ю.Л. Ребецкий лаборатория тектонофизики ИФЗ РАН
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Institute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch 2015
• Subjects: разломная тектоника; tectonophysics; fault tectonics; тектонофизика; Kola Peninsula; Kovdor; kola peninsula
• Online Access: https://www.gt-crust.ru/jour/article/view/134; https://doi.org/10.5800/GT-2011-2-3-0044

The publication presents stress determinations from geological and kinematical indicators of tectonic stress fields, varying in ranks, for the Kola Peninsula. The objective is to determine possible mechanisms of formation of recent structures in the eastern segment of the Baltic shield and to forecast seismogenic and technogenic hazard of fracturing.The study is focused on the Kovdor and Khibin Paleozoic alkaline-ultrabasic blocks. Tectonic stresses are reconstructed by M.V. Gzovsky’s method [1954; 1975] based on identification of conjugated shear systems. Neotectonic stresses are studied by the kinematic method [Gushchenko, 1979] on the basis of measurements of tectonic displacment vectors from slickensides (Figure 2). Local stress data processed by the method for determination of general stress fields provide for reconstruction of main normal stresses which are arbitrarily considered as regional stresses [Sim, 1980; 2000]. This study uses the method of bandpattern distribution of fracturing in fault zones [Danilovich, 1961] which determines the main displacement line on the fault plane.The study of the Zhelezny mining site (Kovdor block, Figures 3 and 4) revealed that elements of fractures of two different ages (centroclinal fractures of the prototectonic genesis and fractures of later tectonic activation) are spatially overlapping due to rock collapse and lacking stability of benches. Numerous inversions and changes of kinematics of relative displacements were reviewed. It was observed that the southeastern wall of the quarry collapsed due to local extension (Fig. 6Band Photos 1 and 2), and a large fault, i.e. a prototectonic fracture, was dipping towards the quarry. Based on the analyses of local stresses at various points of the quarry (Table 1), two ‘regional’ stress fields can be revealed (Figures 7 and 8). The first paleostess field was associated with reverse faults of the WNW subhorizontal axis of compression and the steeply dipping axis of extension. The second field was related to shear faults; its ...