Metasomatic Deposits

mineral deposits that originated during metasomatism. Metasomatic deposits form through the action of hot mineral aqueous solutions circulating at depth when the rock is fully dissolved and new minerals are simultaneously deposited or when the solutions and rock matter interact and mineral aggregates are formed by exchange chemical reaction. In both cases of metasomatic deposit formation the solutions carry out rock elements (alkali metals, alkaline-earth metals, aluminum, calcium, and magnesium) and carry in valuable ore metals (copper, zinc, lead, tin, and others). Carbonate rocks (limestone and dolomite) are most favorable for the formation of metasomatic deposits, and silicate rocks are least favorable.

Metasomatic deposits form intricately shaped beds, frequently with a zonal structure. In accordance with the formation temperature a distinction is made between high-, medium-, and low-temperature metasomatic deposits. The high-temperature deposits include skarn and greisen deposits of ferrous, nonferrous, and rare metal ores. The medium-temperature deposits include hydrothermal replacement deposits, primarily of copper, lead, and zinc ores. Infiltration deposits of uranium and copper are examples of low-temperature deposits.