a mineral deposit that formed later than the enclosing rocks. The mineral composition and chemical composition of epigenetic deposits differ markedly from the composition of the enclosing rocks.
Epigenetic deposits usually occur in the form of veins, lenses, stocks, and pipes that cut through the rocks; zones of mineralization accompanying epigenetic deposits form in the enclosing rocks through their action. Epigenetic deposits include magmatic deposits of titanomagnetites, chromites, platinoids, diamonds, and apatite, as well as certain bodies of sulfide copper-nickel ores. They also include pegmatite deposits of ceramic raw materials, mica, precious stones, lithium, and beryllium and skarn deposits of iron, copper, lead, zinc, and other metallic ores. The broadest group of epigenetic deposits includes hydrothermal vein and metasomatic deposits of ores of the nonferrous, rare, noble, and radioactive metals and deposits of quartz, barite, fluorite, and asbestos. Infiltration deposits of ores of iron, copper, and uranium are also classified as epigenetic deposits.
Epigenetic deposits are contrasted to syngenetic deposits, which formed at the same time as the enclosing rocks.