Barsoomer. I don't think sulfates have been fo...

Barsoomer. I don't think sulfates have been found at Phoenix have they?
One theory about the lack of carbonates at other sites is acidic soil due to the presence of sulfuric acid as indicated by the abundant sulfates, which would tend to decompose the carbonates.
Perhaps the presence of carbonates is due to the lack of sulfates and/or alkaline soil.

Bob Clark