This is unlikely, IMO. There isn't old enough volcanoes in the Atlantic to have eroded right down to a flat, variably soft stone profile like Richat anywhere in the Atlantic.

Maderia is pretty young, Cabo Verde is a bit older, the Azores are probably the oldest but that's it for the atlantic. The volcano that created the Richat structure is millions of years old, most probably, and was probably bigger than Olypmus Mons.