Supergene Processes

processes of the physical and chemical conversion of mineral matter in the upper parts of the earth’s crust and on its surface through the action of the atmosphere, hydrosphere, and living organisms at low temperatures. They consist in chemical decomposition, solution, hydrolysis, hydration, oxidation, and carbonization.

The formation of the weathering crust and oxidation zones of deposits, soil formation, chemogenic and biogenic sediment formation, diagenesis and early epigénesis of sediments, and the formation of the composition of underground waters, rivers, lakes, seas, and oceans take place under the action of supergene processes.

Whereas temperature and pressure are the main factors in endogenic processes, the most important factors in supergene processes are the alkalinity or acidity of the medium and the oxidation-reduction potential. Colloid chemical processes (particularly sorption), as well as recrystalliza-tion of gels, reprecipitation, and ion-exchange phenomena, are highly developed. Biogeochemical processes play a large part. The most important external factor in supergene processes is the climate; the principle of distribution of supergene processes on the earth’s surface is zonality, which was first established by V. V. Dokuchaev (the zonality of soils, the weathering crust, continental deposits, ground waters, and so on). Valuable mineral deposits form as a result of supergene processes.