System organization of disjunctive tectonics of consolidated basement in Dnipro-Donets paleorift. Part 3. Structural-cinematic parageneses of horizontal-shear dislocations zones

Abstract

Formulation of the problem. Getting knowledge of the processes and mechanisms of the rocks tectonic flow is important both for geotectonics and for oil and gas geology as horizontal displacements and rotation of geological blocks in creep dislocations form secondary deformation structures.

Zones of both raised and reduced tectonic stresses are formed in the structural and kinematic parageneses - the so-called "shadow geodynamic zones", in which active fluid-dynamic processes contributing to traps formation and accumulation of hydrocarbons in them, are formed.

Objects of research are secondary deformation structures of tectonic flow (STF). Their newest structural-kinematic parageneses and structured drawings on the surface of Precambrian crystalline basement were studied. Horizontal strike-slip dislocations create their modern architectural structure together with relics of the riftogenic structure.

The purpose of the article. The aim of the research is to study structural manifestation of collisional post-tectonic tectogenesis processes in the architectural structure of the DDP crystalline basement. The research tasks are:

-       To study the types of tectonic movements and mechanisms of tectonic flow deformations in the foundation and identification of the structural patterns;

-       To diagnose morphogenetic types of strike-slip deformation structures of the basement and  structural-kinematic parageneses of tectonic flow.

Methods. According to Plates tectonics theory the tectonic-physics method of structural drawings analysis was used to study the basement tectonics. It allows us to diagnose tectonic movements and deformations of geomass, in particular, its longitudinal, transverse and rotational displacement relative to the extension of the paleoriff structure in various kinematic forms of bending in the horizontal plane, extrusion and injection, as well as the adjoining movements of domains - groups of horizontal strike-slip faults ensembles and their created geological blocks.

Results. According to the results of regional tectonophysical studies:

1. It is established that considerable internal tectonic mobility of the Precambrian foundation at the newest stage of the DDP evolution is manifested in the formation of horizontal strike-slip dislocations zones in the regional system of faults activated in the latest geodynamic stress field.
2. The processes and mechanisms of collision tectonics, which caused formation in the knot zones of the deformation structures of the tectonic flow and the formation of strike-slip structural and kinematic parageneses, have been studied. They are reflected in the tectonic plan of the foundation in the form of characteristic structural elements of the structure and determine its modern architectural structure.
3. The three basic tectonophysical mechanisms of horizontal strike-slip islocations, which differ in kinematics and directions of joint horizontal displacements of block domains, relative to the axis of the paleorief strike, are distinguished:

-       longitudinal elongation under the mechanism of joint antithyroid rotations of blocks on systems of diagonal strike-slip faults;

-       transverse extension of the mechanism of joint synthetic rotation of blocks on systems of orthogonal and diagonal shifts, as well as their complex combination without the rotation of the duplex blocks;

-       tectonic megabout by means of coordinated reciprocating movements without rotational component of adjacent blocks along kinematically identical sub-parallel strike-slip faults.

Scientific novelty and practical significance. In the framework of the newest zones of horizontal strike-slip dislocations, three genesic types of structurally-kinematic parageneses, which correspond to the main geodynamic conditions, are established:

–      contractional duplexes that form ensembles of longitudinal and transverse to reach the paleiorief of positive forms-«palm tree» on the surface of the foundation -structural-tectonic and embrio-tectonic arcs;

–      extensional duplexes of the sprawl, forming the negative forms- «flower structures» or pull-apart basine - lens-like minigrabens;

geological blocks - megabodies of oval form, forming local depressions in the relief of the foun-dation.