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epithermal deposits

Most epithermal ("shallow heat") deposits occur in veins, irregular branching fissures, stockworks, or breccia pipes. Colloform and replacement textures are sometimes recognized, but the majority of epithermal deposits are characterized by open space filling textures (crustification, comb structures, symmetrical banding).

Many epithermal deposits appear to be spatially associated with hot springs and geysers, and these hydrothermal systems may be considered the surface expression of epithermal systems. Alteration of wall rock is predominantly argillic and is accompanied by silicification. Epithelial deposits are commonly associated with large gossans, which are intensely oxidized, weathered, or decomposed rocks that usually form the exposed, upper portions of ore deposits or mineral veins. Common gangue (waste) minerals in the tailings include: quartz, calcite, fluorite, barite, chalcedony, rhodochrosite and dolomite.

Epithermal deposits include a wide variety of ores: Au, Au-Ag, Ag, Pb, Zn, Cu, Sn, Sb, U and Hg.

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