Geochemical mechanism of alkali metasomatism and formation of iron deposits

Discussed in this paper are the processes of albitization and iron activation during the formation of iron deposits, the transport and hydrolysis of iron, chemical reaction characteristic of wall-rock alteration responsible for the localization of iron deposits, the dynamic factors affecting these reactions and systematic variations in pH of ore-forming solutions. A metasomatic series of Na→ Ca→ Fe is noticed when diorite and dark minerals + anorthite + quartz react with 1–3m NaCl solutions at 400°–500°C. Hydrolysis of FeCl₂ has been experimentally studied as a function of temperature and pressure. It is suggested that the pH of ore-forming solutions varies in the direction of alkalic→intermediate→acid→intermediate←kalic from early to late stages.