V. A. Korchin, Subbotin Institute of Geophysics, NAS of Ukraine, O. M. Rusakov, P. A. Burtnyi, E. E. Karnaukhova, Subbotin Institute of Geophysics, NAS of Ukraine, Subbotin Institute of Geophysics, NAS of Ukraine, Subbotin Institute of Geophysics, NAS of Ukraine
Purpose. Based on laboratory PT-studies of rocks and their joint analysis with the data from the regional profile RP-17, the aim of this research is to reveal the origin of the low-velocity zones in the Transcarpathian depression as zones of thermobaric rock decompaction and to elucidate the relationship of these zones with earthquakes and hydrocarbon fields. Methodology. The essence of such an approach is the comparison of the DSS information with experimental data on the physical parameters
more » ... ysical parameters of rocks at high pressures and temperatures. For this purpose, we used the results e from high PT measurements of physical parameters on rocks analogous to those from the region under study. Results. Having analyzed the findings of the laboratory PT-experiments, we developed the method of petrophysical thermobaric modelling. This method is based on the characteristics of the "granitoid" type rocks from the Ukrainian Shield and the results of the joint interpretation of these data and information on the regional deep seismic sounding profiles from this tectonic unit. These approaches and techniques were applied to the analysis of the data from Transcarpathia, in particular, to the RP-17 regional profile. Two decompaction zones of the thermobaric origin were revealed along the profile coinciding with low seismic velocity zones. They are supposed to be effective regional traps for the mantle fluids, especially for hydrocarbons which under high pressure, temperature, and decompression penetrate into the near-surface layers of the sedimentary cover and form mineral deposits. In the decompaction zones shallow earthquakes with low magnitudes become activated. They widen the decomposition domains and facilitate the movement of deep hydrocarbons to the location within them. Originality. For the first time, it was shown that low velocity zones (the region of thermobaric decompaction of mineral matter) under certain pressure and temperature in the Еarth's crust of "thermoactive" region, including Transcarpathia, are its integral part; they are inevitably formed in the process of warming up of the Earth's interior during its "thermoactivation". Horizons of thermobaric decompression of rocks, which under the influence of stresses, multidirectional deformations, and vibrations, acquire the properties of strongly dislocated media forming extensive migration channels of fluids, "degassing pipes". They provide the movement of useful mineral media to the surface and the zones of intense relaxation of tectonic stresses, especially in the form of earthquakes. Practical significance. The results of the studies give an opportunity to clarify the geological and structural features of the structure of the Earth's crust of Transcarpathia, to adequately interpret the spatial distribution of geophysical fields and to decipher the features of local geodynamics and seismotectonic process, to clarify the level and nature of geo-ecological hazards, to more effectively predict and study deep regional distribution of mineral resources.
doi:10.23939/jgd2020.01.081 fatcat:r2i22muzurd43jt2xkzj233ro4