MODEL OF THE DEVELOPMENT OF THE OVERLAP OF SPREADING AXES

Abstract

A fine structure has recently been identified in ocean rifts with high spreading rates. The mechanism of quasibrittle failure of the basaltic layer (the crust) in the axial zone of a rift above a magma chamber as a result of development and interaction of macrojoints (cracks) in it has already been invoked in the literature as a possible explanation of the overlap of the axes of spreading. In the present paper we discuss the results of our experimental modeling of this mechanism, on the basis of which we develop a model of the development of zones of overlap of the axes of spreading (OAS). According to our model, the ridges are former axial zones of the rift in which volcanic activity ceases abruptly as a result of sidewise displacement of the spreading axis. The products of hydrothermal activity overlying the crests of these ridges are not buried under subsequent magma flows. This conclusion is likely to be important in determining seafloor zones that are promising for sulfide prospecting.