Geophysical Journal | 2011 volume 33 6

Thermobaric petrophysical modeling of lithosphere of the Earth's crust areas of the Ukrainian Shield with zones of low seismic velocities

© Korchin V.A., Burtnyi P.A.

Cross-section of rocks distribution with depth along the central part of DSS geo-traverse IV, which crosses several zones of low seismic velocities (ZLV) has been plotted using the method of petro-physical thermobaric simulation. Deep horizons of the Earth's crust within this part of the profile (up to 40 km) are formed by plagiogranites, diorites, enderbites. As a rule, ZLV found at the depth 5-15 km are not dependent from the mineral composition of rocks and are first of all determined by deep temperature regimes of the crust of this area of the USh. Zones of low velocities appear in those cases when temperature gradient at the corresponding depths exceeds some definite threshold and pressure is not able to compensate violation of integrity of mineral medium produced by the action of temperature. Temperature fluctuations at the depths 7-20 km may change parameters of zone of low velocities up to their disappearance. Relation of ZLW configuration (their intensity, extension along the depth, deflation of velocity) to heat flows (HF) measured in the studied area is observed. Intense ZLV correspond to higher HF, within the areas with low HF zones of low velocities are weak or absent.

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