Models of fracture orientation at oblique spreading centres

Abstract

Three models are proposed for the orientation of extensional faults and dykes at mid-ocean ridges based on their relationship to the ridge axis and the relative plate separation vector. These models predict four ridge geometries allowing them to be tested by orientation data from 17 different sites within the Earth's oceans. A transtensional model is shown to be generally applicable to the structure of mid-ocean ridges, with special conditions required for a departure from it. Spreading rate influences ridge geometry with intermediate and fast spreading ridges more likely to have an orthogonal spreading geometry, which is an end member case of the transtensional model.