RomUkrSeis profile: a model of the deep structure of the lithosphere and its geological and geophysical interpretation. P. II. The nature of geophysical heterogeneities based on complex analysis

• Main Authors: Makarenko, I.B., Burakhovych, T.K., Kozlenko, M.V., Murovskaya, G.V., Kozlenko, Yu.V., Savchenko, O.S.
• Format: Article
• Language: Ukrainian
• Published: Subbotin Institute of Geophysics of the NAS of Ukraine 2025
• Subjects: RomUkrSeis profile; deep structure of the lithosphere; lithosphere-asthenosphere boundary; geological and geophysical interpretation; Teisseyre-Tornquist Zone; Transylvanian Basin
• Online Access: https://journals.uran.ua/geofizicheskiy/article/view/317035

For the first time, the lithosphere deep structure was analyzed using the RomUkrSeis profile. The study incorporated the velocity, gravity and geoelectric models applying information about the lithosphere-asthenosphere boundary, thermal and magnetic field anomalies and signs of modern activation. The following features of the main layers of the Earth’s crust and upper mantle were identified. In the upper crust of the Apuseni Mountains, high-density heterogeneities can be interpreted as ophiolite complexes. The detected deconsolidation of the upper crust of the NE Apuseni Mountains and part of the Transylvanian Basin is probably related to a detachment at the depth of 6 km. The nature of density heterogeneity at depths of 6-12 km under the Inner Eastern Carpathians can be caused by igneous rocks or be considered as a sedimentary depression, which extends to the southwest. The relief of Moho divide beneath the Apuseni Mountains was detailed, where it reaches a depth of 38 km. It was found that the subduction or rise of the upper edge of the asthenosphere matches with the hypothetical tracing of crustal-mantle faults to it, namely: Western Apuseni, Bohdan-Dragos Voda, Krakowiec-Bikaj (Uzhochtskyi), Frazin (Transcarpathian), Rava-Ruskyi, Rivnenskyi, Pridnistrovskyi, Podilsky. A lithospheric zone under the Transylvanian Basin was discovered, which penetrates the mantle and may be a unique system of fluid migration channels, which cause the formation of methane deposits. The nature of the anomalous electrical conductivity of the Carpathian-Pannonian region confirms the fluid concept and satisfies the interpretation of seismic and gravity models. In the Teisseyre-Tornquist zone, gravity modeling confirmed rock decompression of sedimentary depression, upper crust and a narrow mantle wedge in the Moho division according to seismic data and detected densification in the lower crust and upper mantle. According to electromagnetic data, the zone is located between electrical conductivity anomalies in the crust. It has a thick lithosphere up to 100 km. The probable location of the Teisseyre-Tornquist zone is considered in the profile cross-section. The zone is revealed by geophysical heterogeneities (density, geoelectric, thermal) and is explained by warming, as well as fluid saturation (possibly partial melting) of crustal and upper mantle rocks. A cluster of gas fields in the area of the RomUkrSeis profile (in the Transylvanian Basin and the frontal part of the Carpathians) may be related to faults Bistrica Pride, Frazin (Transcarpathian), and Rava-Ruskyi, which can probably be considered as fluid-magmatic channels