K/Ar ages and stress pattern in the Azores: Geodynamic implications

We have dated by the K/Ar method the oldest volcanic formations known in the Azores archipelago. The results show a development of this oceanic island system from 5.5 m.y. to the present day.The age pattern is not compatible with a simple migration over a small fixed hot spot, but, plotting tectonic directions which control the volcanism versus age and distance to the Mid-Atlantic Ridge, a simple relationship seems to appear showing an anisotropic but fixed distribution of stress orientation at least for the last 0.7 m.y.