Deep geoelectric studies of the Troyankiv and Tarasivka metabasite massifs of the Golovaniv suture zone

• Дата: 2019
• Автори: Kushnir, A. M., Burakhovich, T. K., Ilyenko, V. A., Shyrkov, B. I., Nikolayev, I. Yu.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: Subbotin Institute of Geophysics of the NAS of Ukraine 2019
• Теми: the Golovaniv suture zone; 3D geoelectric model; magnetotelluric sounding; magneto-variational profiling; deep structure; anomalies of electro-conductivity
• Онлайн доступ: https://journals.uran.ua/geofizicheskiy/article/view/190066
• Назва журналу: Geofizicheskiy Zhurnal

Results of experimental observations of low-frequency natural alternating electromagnetic field of the Earth of external ionospheric-magnetospheric origin, conducted in 2017 – 2018 in the territory of the Yatran block of the Golovaniv suture zone of the Ukrainian shield have been presented. After application of procedures of synchronous rating of transmitting operators of MT/MV fields with the help of the program complex PRC-MTMV complex induction parameters have been obtained for the periods from 50 to 10000 s. and amplitude curves of visible resistivity and phases of impedance for the wide range of periods from 10 to 10000 s. Qualitative analysis of experimental parameters has demonstrated that the Troyaniv and the the Tarasivka structures are specified by a very complicated structure in geoelectric aspect. On the one hand, it is the presence of surface local three-dimensionality indicated by considerable discrepancy of curves ρпin prevailing majority of observation sites. On the other hand it is the dramatic change of flow of telluric currents in the eastern part of the pad and the influence of high-conducting Yemyliv and Krasnopolyana faults situated to the southwest. Three-dimensional geoelectric models of the Tarasivka and Troyankiv structures plotted with application of legacy software Mtd3fwd differ essentially. If in the first one we can distinctly specify the surface up to 100 m and the deep 2―10 km layers, the last ones with essential loading at that and some blocks spatially coinciding, in the second one in addition to well-developed surface up to 100 m layer several local zones at different depth levels exist but only up to top 4 km which alternate with layers of high resistance.  An interesting point is the presence in both models in the south (or between them) sub-latitudinal deep conductors 4―7 ― 10 km, spatially coinciding with geologic-geophysical structures. And though within geological margins the structures do not completely manifested in abnormal electric conductivity, the unifying feature of both models is a fragmental manifestation of low values ρ from 5 to 100 Ohm·m in the bodies of metabasite massifs exactly. But we can certainly affirm on high conductivity of faults of different rank and their surrounding cross-sections. High electric conductivity can be explained by a special composition of rocks of the Earth crust (graphitization, sulfidization etc.) or fluidization of different origin.