KINEMATIC AND MORPHOMETRIC PATTERNS IN THE STRUCTURE OF OVERLAP ZONES OF MID-OCEANIC RIDGES SPREADING AXES

Abstract

An analysis was made of kinematic and morphometric characteristics of zones of overlapping spreading centers - structures illustrative of spreading ridges with fast and intermediate spreading rates. Three levels of overlap have been distinguished: Small, with a width (w) of ≤ 3 km, large, with w = 3-20 km, and great, with w = > 20 km. The length of the segments of the rift axis, which are enclosed between the neighboring overlaps, varies greatly. For small overlaps it averages 50-70 km; for large and great, 100-120 km. The characteristic depths of the central basin make up tens of meters for small overlaps, and hundreds of meters for large and great overlaps. The form of overlaps can be different in plan. In small displacements the overlapped axes are mainly rectilinear; and large displacements are characterized by the axes divergence from one another before they converge; in great displacements the axes converge without any divergence from one another. The relationship between the morphometric parameters of overlaps and spreading rates are considered. Their width for large and great overlaps, the length of the constituent segments, and the depth of the central depression do not depend on the spreading rate. These parameters are governed by the development stage of the overlap. The analogous characteristics of small overlaps depend largely on the spreading rate. It is shown that the formation and development of overlaps depend on the spreading rate and /or the thickness of the brittle layer of the crust. At their certain values, the overlap structures of overlapping spreading centers can form on the slow spreading ridges.