Would there a be a form of acid rain from this sulphuric acid? Perhaps rain like this might erode differently to pure water. Having a pure CO2 atmosphere rins into some problems when you have signs of water flows on the surface in the past. CO2 freezes at a relatively low tenperature compared to oxygen so low temperatures would have been on the edge of causing the atmospheric pressure to collapse.

In this case the low air pressure would cause ice to sublimate not form water, and cause the ice to be locked at the poles and the lower latitudes to be dessicated. While this (White Mars theory) fits well with the dryness of Mars and the olivine it doesn't fit with what so many geologists see as glaciers, ancient seas (Amazonis Planitia, Utopia Crater), outflow channels (Margaritifer Sinus), etc.

So to have times when water did flow insignificant amounts oxygen was probably necessary for higher air pressure. Perhaps the olivine came from eruptions at Tharsis, Olympus Mons, and Elysium Mons over time and was distributed over the planet in dust storms.