The structure of the Earth's crust and the uppermost mantle of the Kirovograd Block of the Ukrainian Shield by DSS data (Babanka-Pyatikhatki and Cherkassy-Noviy Bug profiles)
© T.V. Ilchenko
New variants have been given for velocity models of the Earth's crust and near-crustal mantle along the DSS profiles Babanka-Pyatihatki and Cherkassy-Noviy Bug which intersect the Kirovograd Block of the Ukrainian Shield, including the transition zone between the Novoukrainian granite massif and Korsun-Novomirgorod Pluton.
The uppermost crystalline crust layer of 4-5 km thick is made of blocks, whose velocity structure is determined by their rock types at their basement. Within the layer, velocity only grows with depth. Deeper, within the depths 4-5 up to 20 km, velocity is repeatedly inverted. A crustal positive velocity anomaly coincides with the Pluton region and probably characterizes its mafic rocks complex. The anomaly reduction with depth is a geophysical reason to suppose a crustal origin of the Pluton. The Moho rise and intra-mantle boundary contour outline a near-crustal lens-shaped layer under the Pluton. The layer's formation was possibly related to the Pluton development and therefore such as occurred later than other large geodynamic events in the region. The process itself must have been in this case a transformation of some lowermost crustal rocks into mantle ones.
The bottom of near-crustal lens had possibly been the cover of the mantle before the Pluton formation started. Its relief as well as the Moho's one to the East of the Pluton is supposed to be created by mechanical movements and before the lowermost part of the present upper crust had been developed.