Weathering and Sedimentation

Sedimentary processes start with weathering of rocks, a chemical breakdown generated through the action of water and atmospheric CO₂. A general reaction is the weathering of potassium feldspar (KAlSi₃O₈) to create the clay mineral kaolinite:

CO₂ works to give acid in this reaction, and weathering is accelerated through living organisms that give CO₂ by respiration and decay. An additional step in this procedure leads to extremely insoluble Al(OH)₃:

So rocks are transformed through weathering, with soluble ions like K+ being washed out and insoluble resistates remaining. Several significant sources of elements are of this form, that involving bauxite Al(OH)₃, rutile TiO₂ and cassiterite SnO₂.

The action of atmospheric oxygen on soluble ions might produce insoluble oxidates like Fe(OH)₃ and MnO₂ from Fe²⁺ and  Mn²⁺, correspondingly. Another elements pass into the ocean and become deposited in several ways: as biogenic deposits like CaCO₃ and SiO₂, that originate like the shells of marine organisms, or as evaporates like NaCl produced through evaporation of salt lakes.