Pneumatolytic Deposits

mineral deposits formed by the action of the hot mineralized vapors and gases released by solidifying magma in the interior of the earth as a consequence of pneumatolysis. Greisen and albitite high-temperature hydro-thermal and metasomatically altered pegmatite deposits are formed. These deposits belong to the pneumatolytic group and occur as veins, stockworks, and irregularly shaped masses measuring as much as several kilometers long. Pneumatolytic deposits are characterized by metasomatism with the formation of minerals containing volatile components (H₂O, F, B).

The typical minerals of pneumatolytic deposits are quartz, topaz, muscovite and other micas, albite, torumaline, and fluor-ite. These make up the ores of uncommon metals, such as W, Sn, Be, and Li. Such ore deposits are generally found in regions of granite development, for example, the tin and tungsten deposits of Eastern Siberia and the Kazakh SSR in the USSR, of the Erzgebirge (Ore Mountains) in Czechoslovakia and the German Democratic Republic, and Malaysia.

Pneumatolytic deposits are not always recognized because it is difficult to distinguish them from hydrothermal deposits. In such cases, they are classified as postmagmatic hydrothermal deposits.