MODELS OF FRACTURE ORIENTATION AT OBLIQUE SPREADING CENTERS

Three models are proposed for the orientation of extensional faults an d dykes at mid-ocean ridges based on their relationship to the ridge a xis and the relative plate separation vector. These models predict fou r 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 ridg es, with special conditions required for a departure from it. Spreadin g 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.