Metasomatic Deposits

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.

REFERENCE

Smirnov, V. I. Geologiia poleznykh iskopaemykh, 2nd ed. Moscow, 1969.

V. I. SMIRNOV

References in periodicals archive ?
A-Hydrothermal Metasomatic deposits in carbonate and dolomitic rocks: Through this process mechanism, when hydrothermal solutions penetrate into the dolomitic rocks, because the ionic radius of calcium is about 36 % bigger than that of the Magnesium, these two elements therefore cannot replace one another isomorphically; however because the Iron ionic radius is not so much different from that of the Magnesium, a series of isomorphic minerals like Magnesite, Hontite, Bronzitite and etc.
Graphite deposits of commercial interest occur widely in regionally or thermally metamorphosed sedimentary rocks and in hydrothermal and metasomatic deposits.