E. A. Bataleva

Underthrusting of Tarim beneath the Tien Shan and deep structure of their junction zone: Main results of seismic experiment along MANAS Profile Kashgar-Song-Köl

The results of reflection CMP seismic profiling of the Central Tien Shan in the meridional tract 75–76° E from Lake Song-Köl in Kyrgyzstan to the town of Kashgar in China are considered. The seismic section demonstrating complex heterogeneous structure of the Earth’s crust and reflecting its near-horizontal delamination with vertical and inclined zones of compositional and structural differentiation was constructed from processing of initial data of reflection CMP seismic profiling, earthquake converted-wave method (ECWM), and seismic tomography. The most important is the large zone of underthrusting of the Tarim Massif beneath the Tien Shan.

Nature of electric conductive layers of the upper crust and infrastructure of granites of the Central Tien Shan

We studied the infrastructure of granite massifs of the Central Tien Shan and its correlation with the electric conductive layer of the upper crust, which made possible to reveal new peculiarities of the structure of the granite layer in the region and to clarify the nature of low resistivity layers.

New data on the deep structure of the South Kochkor zone of concentrated deformation

Based on a complex study of the upper crust structure in the southern margin of Kochkor basin (Northern Tien Shan), including study of the structure of the Cenozoic sedimentary cover, the deep geoelectrical structure, the structural unconformities, and occurrences of recent deformations in the basement rocks, new geological–geophysical cross sections are constructed. The cross sections show both fault structures that penetrate the cover from the basement and flat interplate detachments with related fold-overthrust structures. The comparison of the cross sections has established the absence of common planes of fault extensions along the entire margin of the hollow, except for the zone where the margin and the hollow adjoin, which can be caused by the zones of dynamic influence of secondary faults, the zones of fracturing, and the zones of cataclasis of blockwise disintegrated granite massifs.

The state of the lithosphere in the junction zone of Tarim and Tien Shan according to the petrological interpretation of the magnetotelluric data

The geological-geophysical and petrological-geochemical studies of the Earth’s crust and upper mantle are combined to estimate the state of the lithosphere at the junction zone of Tarim and Tien Shan. The laboratory measurements of electric conductivity in the rocks sampled from the upper mantle and lower crust considered against the geoelectrical and thermal models revealed lherzolite, granulite, and eclogite massifs in the deep section of the Tarim and Tien Shan junction zone. The experimental results suggest that the crustal thickness in the southern Tien Shan attained 35–40 km 70 Ma ago.

On the question of the interrelation between variations in crustal electrical conductivity and geodynamical processes

The behavior of the variations in the crustal electrical conductivity in a wide range of periods is studied from the data of magnetotelluric soundings (MTS) during the Kambarata experiment (a strong industrial explosion to construct the blast-fill dam on the Naryn river), as well as at Aksu, a stationary geophysical monitoring point. The concept of the interrelation between the stress-strain state of the medium and the change in the apparent electrical resistivity, which is based on the idea of the redistribution of mineralized solutions between the crack networks, is confirmed experimentally. A procedure of azimuthal monitoring is developed, which allowed us not only to identify the anomalous changes in the module and phase of apparent resistivity but also to establish the directions of their maximum increases and decreases (the axes of compression and tension). For 34 points of deep MTS in the territory of Central Tien Shan, the depth intervals in the upper crust that are most sensitive to the changes in the stress-strain state of the medium are established. The variations in the electrical conductivity are compared with the solar-lunar tidal impacts. It is shown that by analyzing the recorded time series, it is possible to recognize the characteristic signs of the changes in the stress-strain state of the medium that are caused by seismic events.

Specific Features in the Deep Structure of the Naryn Basin–Baibichetoo Ridge–Atbashi Basin System: Evidence from the Complex of Geological and Geophysical Data

New magnetotelluric data were obtained for the Karabuk profile crossing the Naryn basin–Baibichetoo Ridge–Atbashi basin geodynamic system (Central Tien-Shan). The complex geological–geophysical cross section along the profile provides a good agreement between the surface tectonic structures and the deep geoelectric model. The electric conductivity anomalies revealed as subvertical conductors striking along the flanks of basins may be explained by the zones of dynamic influence of faults and cataclasis of granite.

Correlation dependences of electromagnetic and deformation parameters

In-situ monitoring observations are carried out, and correlation analysis aimed at estimating the dependences between the electromagnetic parameters (variations of apparent resistivity, the impedance phase, components of the impedance tensor, and deformations of the daylight surface on the territory of the Bishkek geodynamic polygon) is performed. A new approach to the explanation of the physical mechanism forming variations in electrical conductivity of the medium is proposed on this basis.