Can the atmosphere affect the composition of igneous rocks? Recently I was reading 'How to build a habitable planet' by Langmuir and Broecker and in chapter 15 they speak about how Life has led to a difference in oxidation potential in the atmosphere, essentially leading to the earth becoming a fuel cell. They also spoke about how this led to certain ions being oxidized - ie uraninite to uranyl oxide, iron to hematite.

I was wondering if this could mean that as atmospheric composition would affect the sea floor, when this subducted it would affect the melt of the mantle - as far as I'm aware, it is the dehydration of the subducting slab which allows for the hydration, and therefore melt, of the mantle in regions such as Japan. If the subducting slab's composition is affected by the atmosphere, could this have any effect on the composition of the igneous rocks formed? Would this be detectable?

Thank you.
I figure you're looking for more exotic examples, and some geologists may well have some offhand, but I want to say "yes" because of the example of carbonatite rocks described in this geology page from San Diego State University:


  Carbonatites are perhaps the most unusual of all lavas. They are
  defined, when crystalline, by having more than 50% carbonate
  (CO3-bearing) minerals, and typically they are composed of less than
  10% SiO2.


Which would rely on the carbon cycle and the deposition of atmospheric CO2 onto the seafloor by biological processes.

However:


  Some scientists believe that the Ca-carbonatites are generated by
  fractional melting of crustal carbonate rocks. However, others believe
  that the Ca-carbonatites are not primary magmas at all, but rather
  derived from the alteration of Na-rich natrocarbonatite lavas.


There is an interesting paper in GeoScienceWorld titled Atmospheric K-feldspar as a potential climate modulating agent through geologic time that addresses your topic as the author tries to estimate K-feldspar (Kfs) flux through geologic time -- which addresses your question from the other direction: assessing atmospheric content (in some cases simple dust deposition) over billions of years by evaluating its traces in the geological record.