Geophysical Journal | 2002 volume 24 5

Tensor field of magnetic susceptibility of the Kryvyi Rig Basin

© Kovalenko-Zavoisky V.M., Ivashchenko I.M.

The magnetic susceptibility anisotropy of the rocks of the Kryvyi Rig basin is due to layering and deformation. The tensor of deformational origin is associated with geometric elements so that the short tensor axes are perpendicular to the wings but not to the axial surfaces of folds and the long axes are, asa rule, parallel to their hinges. Hence it is concluded that during the folding the stress relaxation was sufficiently fast to allow the rocks to reach the balance relative to the varying external stress. After having exhausted the resources of the energy decrease by, folding oder together with it, the rock flows parallel to the hinges, which explains the direction of the long axes along the hinges. The conformity of the tensor field of the susceptibility of the Kryvyi Rig basin and the enclosing plagiogranites of the Ingulets massif allows to state that the archean plagiogranites drilled by the ultradeep boreholl undervent in Lower, Proterozoic dynamometamorphism during which the Kryvyi Rig rock series was folded. The next stage of the Kryvyi Rig structure evolution was the plunge of the Saxaganska and Annovska monocline in to plagiogranites under the gravity effect, while the western fold of the Kryvyi Rig basin was "afloat". The correlation between the direction of the elongation of the iron-ore bodies of the Saxaganska syncline with the direction of the long axes of the susceptibility axes confirms the fact that the ore formation is associated with the irony quartzite deformation.

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