Mars – spreading volcano

At http://specialpaper.gsapubs.org/content/470/115.abstract 'Is Tharsis, Mars, a spreading volcano?' – it is thought Tharsis Rise on Mars is spreading outwards and that has produced rifting at the summit with radial tear-fault systems associated with folding round its periphery. It is said by this geological attempt at understanding the feature to be analogous to a terrestrial mid-ocean ridge – without the corresponding subduction zones. Instead, it is alleged, plates on Mars obducted over the Martian crust.