Depletions
Excellent. Minuses are as important as pluses.
I don't think it's andesite either, but based upon speculative mineral shapes at the time, it was a logical progression.
Felsics wouldn't make too much sense either. What about carbonatites? Rare, Carbonate rich volcanics with mantle origins and odd mineral assemblages, including apatite and titanium minerals.
Wishstone may be completely alien to this setting, so setting it against the average composition of other Gusev rocks might be an improper normalization.
I'm not sure, but I think the elemental order has to do with the specific wavelengths of the TES signal. The graph certainly doesn't make that clear.