Jökulsárlón (Glacier Lagoon) with Öræfajökull in the background.
The position of Öræfajökull fits exactly to the arrangement of convection cells under Iceland. Recently, quite many earthquakes were measured below the SW part of the mountain. At the 64th parallel all the four layers are equally thick. It is the latitude where the convective layers from north and south meet and arrange themselves in a regular pattern. You can see a drawing showing this at the front page of this website. Accordingly, the flow of magma is probably originated about 120 km below the surface, first flowing through the ductile part of the tectonic plate and then making its way with help from the constant work of the other three layers on the same point up through the brittle part of the crust.
This is of course not easy to understand at first, but along the 64th latitude both Hekla and Öræfajökull are over crossings of these four convective layers.
As this convection cell system can be put into a mathematical form according to some very simple preconditions, we can understand why Öræfajökull has this location on the 64th parallel. Is that enough for us?