scholarly journals Geoelectric heterogeneities of the Kerch iron ore basin

2021 ◽  
Vol 43 (5) ◽  
pp. 165-180
Author(s):  
I. Yu. Nikolaev ◽  
T. K. Burakhovych ◽  
A. M. Kushnir ◽  
Ye. M. Sheremet
Keyword(s):  
Electrical Conductivity ◽  
Upper Mantle ◽  
Iron Ore ◽  
Earth’S Crust ◽  
Crust And Upper Mantle ◽  
Near Surface ◽  
Low Resistivity ◽  
Kerch Peninsula ◽  
Mud Volcanism ◽  
Earth's Crust

The three-dimensional geoelectric model of the Earth’s crust and upper mantle of the Kerch Peninsula has been built for the first time based on the results of experimental observations of the Earth’s low-frequency electromagnetic field, carried out in 2007—2013 by the Institutes of the National Academy of Sciences of Ukraine. Its physical and geological interpretation and detailing of the near-surface part were carried out according to the data of the audiomagnetotelluric sounding method to study the deep structure of the Kerch iron ore basin. To the east of the Korsak-Feodosiya fault along the southern part of the Indolo-Kuban trough (in the north of the South Kerch and almost under the entire North Kerch zones), a low-resistance anomaly (ρ=1 Ohm∙m) was found at depths from 2.5 km to 12 km about 20 km wide. Its eastern part is located in the consolidated Earth’s crust and is galvanically connected with surface sedimentary strata, while the western part is completely in sedimentary deposits. The anomaly covers the territory of the Kerch iron ore basin and occurrences of mud volcanism. The characteristics of the upper part of the layered section of the Kerch Peninsula in the interval of the first hundreds of meters were obtained from the results of one-dimensional inversion of the audiomagnetotelluric sounding data (frequency range 8—4000 Hz). It is shown that the first 15 m of the section, corresponding to Quaternary deposits, have resistivity values up to 1 Ohm∙m. Below, in the Neogene sediments, the electrical resistance increases to values of 5 Ohm∙m and more. Both horizontally and vertically, the distribution of resistivity values has a variable character, manifesting as a thin-layered structure with low resistivity values. Possibly, such areas have a direct connection with the channel for transporting hummock material and gases. A connection is assumed between the low-resistivity thin-layered near-surface areas, a deep anomaly of electrical conductivity in the upper part of the Earth’s crust, and the likely high electrical conductivity of rocks at the depths of the upper mantle with iron ore deposits, as well as the manifestation of mud volcanism. The heterogeneity of the crustal and mantle highly conductive layers may indicate a high permeability of the contact zones for deep fluids.

scholarly journals Geoelectrical inhomogeneities of the Crimean region as the seismicity and oil-gas potential zones

2021 ◽  
Vol 43 (1) ◽  
pp. 69-92
Author(s):  
A. Kushnir ◽  
T.K. Burakhovich
Keyword(s):  
Upper Mantle ◽  
Earth’S Crust ◽  
The Black Sea ◽  
Northwestern Part ◽  
Crust And Upper Mantle ◽  
Contact Zones ◽  
Crimean Peninsula ◽  
Near Surface ◽  
Conductivity Anomalies ◽  
Earth's Crust

The three-dimensional geoelectrical model of the Earth’s crust and upper mantle of the Crimean region and adjacent territories has been built for the first time. It is based on the results of the Earth’s low-frequency electromagnetic field experimental observations, conducted in 2008—2013 by the Institutes of the National Academy of Sciences of Ukraine. The subvertical conductive zones or contacts of the different resistivity mainly in the near-surface layers coincide with the fault structures, most of which are confined to the boundaries between the different tectonic elements, such as the Scythian Plate and Mountain Crimea, North and South Kerch Zones and the other faults: Chongarskiy, Melitopol-Novotsarytsynskiy, Korsarsko-Feodosiyskiy, Gornostaevskiy and Kerch-Chkalivskiy. The Mykolayiv and West Crimean fault systems occur as large separate submeridional conductive zone. Deeper in the Earth’s crust and upper mantle, geoelectrical inhomogeneities are transformed into the subhorizontal structures (layers) and manifest themselves in regional anomalies. This fact may indicate the high permeability for deep fluids of contact zones during their formation. The deep sublatitudinal structure in the Earth’s crust is confidently traced, in the west it confirms and details the well-known Tarkhankut anomaly, and continues through the central Crimea to the northwestern part of the Kerch Peninsula. It is assumed that there is the strong sublatitudinal anomaly in the interior of the northwestern shelf of the Black Sea and in the northeastern part of the Kerch-Taman Depression at the crust — upper mantle boundary, it is contouring the Crimean Peninsula. The ultradeep fluid manifestation zones obtained according to seismotomography, the conductivity anomalies in the Earth’s crust and the upper mantle, increased heat flow and the spread of the earthquake hypocenters confirm the relationship between the Crimea seismicity and collision processes. It is shown the spatial coincidences of the hydrocarbon manifestations and the isolated conductivity anomalies, which are characterized by subvertical channels galvanically connected to sediments, or subvertical contact zones of different resistivity, which are observed not only in the Earth’s crust but also in the upper mantle layers (60—90, 110—140 km) and may cause the superdeep fluid inflow.  

A study of the Earth's crust and upper mantle using travel times and spectrum characteristics of body waves

1970 ◽  
Vol 60 (6) ◽  
pp. 1921-1935
Author(s):  
B. M. Gurbuz
Keyword(s):  
Upper Mantle ◽  
Body Waves ◽  
Earth’S Crust ◽  
Travel Times ◽  
Time Data ◽  
Crust And Upper Mantle ◽  
Contour Maps ◽  
Spectrum Characteristics ◽  
Earth's Crust ◽  
Early Rise

Abstract The aim of this paper is to investigate the velocity distribution and structure of the Earth's crust and upper mantle from the close collaboration of theory and experimental results of travel times and spectrum characteristics of body waves. The interpretation was based on 38 seismic records which were obtained from the “Project Early Rise” experiment during July 1966. The results refer to the area bounded by latitudes 49°W and 51°30′ and longitudes 93°W and 98°W. A least-squares analysis of the travel-time data was made and the uncertainties of the slopes, intercept times, and corresponding velocities were determined. The observed wide-angle reflections were used to calculate the root mean square velocities applying the T2 - X2 method. Depth calculations for the velocity discontinuities and seismic depth contour maps were made. A model was constructed, and the validity of the proposed new model was tested by comparing the observed travel times, spectrum-amplitude ratios, and relative phase shifts of body waves with theoretically expected values. Evidence is given for three discontinuities in the Earth's crust with velocities of 6.11 ± 0.01 km/sec, 6.8 ± 0.08 km/sec, and 7.10 ± 0.04 km/sec at average depths 18 ± 2 km and 25.5 ± 0.9 km. Velocities in the uppermost part of the mantle were determined as 7.90 ± 0.05 km/sec and 8.48 ± 0.05 km/sec with interfaces at the average depths of 34 ± 1 km, and 47 ± 1 km, respectively.

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