Structural, tectonic and fluid-dynamic aspects of deep degassing of the black sea megatrench

Purpose.The problematical and controversial issues related to active gassing, deep structure, formation and evolution of the Black Sea are discussed. Methods. Geological and geophysical data (sonar, seismic and seismological research, involving potential fields' modelling results), obtained in recent years in the Azov-Black Sea region, were subjected to complex interpretation. Findings. It is proved that there is a significant difference in the formation mechanisms of the main structural units of the Black Sea megatrench – the Western and Eastern trenches. Thermodynamic conditions, a limited amount of biomass in the sedimentary filling of the Black Sea megatrench and the confinedness of the gas seeps to the consolidated crust split testify to the abiogenic nature of methane. Interaction of powerful rising hydrocarbon flow with different structures of the sedimentary mantle and basement led to the formation of numerous hydrocarbon deposits in the Black Sea megatrench. Originality. Analysis of the plume-tectonic mechanism of deep degassing made it possible to assess the role of geodynamic factors related both to the evolution of the Black Sea megatrench and the genesis of hydrocarbons from a new perspective. Practical implications. Analysis of deep fluids migration routes and deep energy unloading zones will allow to develop a new strategy for oil and gas deposits exploration and to work out a non-standard approach to the evaluation of hydrocarbon reserves in the Black Sea oil and gas megabasin.