Geophysical Journal | 2015 volume 37 5

Low velocity zones of thermobaric origin in the crystalline crust

© V.A. Korchin, 2015

The paper presents a new hypothesis of origin, existence and disappearance of crustal low velocity zones (LVZs), discovered by the DSS method as elastic anomalies of the Earth's crust. Complex changes are experimentally obtained for Vp,s=f(PT)=f(H) in rocks (regions of velocity inversion are revealed). There is cataclastic decompaction of mineral medium in them - dilatancy phenomenon. Their configuration, location and thermodynamic conditions coincide well with the DSS elastic anomalies. They arise only when the temperature gradient exceeds the certain threshold in the crust and the pressure cannot compensate thermal disturbances of rocks. The presence of LVZs is the objective reality and they can occur everywhere in the Earth's crust. Their thickness can increase due to the increase of intensity of thermal regimes or the zones can disappear due to lowering heat in the lithosphere. Based on the study of relationship between pore space and velocity, an increase is revealed in rocks porosity and joint with depth of the LVZs that stipulates increasing migration and localization of different fluids and hydrocarbons of a deep origin. The LVZs and related to them deep events and processes are the most accessible to study using different geological-geophysical methods, including super-deep drilling. This makes it possible to perform the most detailed and promising studies aiming to search for mineral resources and clarify the deep structure of the Earth, as well as to explain and predict crustal earthquakes.

Key words: physical properties, low velocity zones, thermal regimes, decompaction of rocks, porosity, hydrocarbons localization.

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