Epithermal Deposit - Mining Fundamentals

Epithermal ("shallow heat") deposits are mineral deposits comprising veins, irregular branching fissures, stockworks, breccia pipes, or replacement bodies. They contain precious metals or, sometimes, base metals that are usually found among volcanic or sedimentary rocks.

In most cases, epithermal deposits are characterized by open space filling textures, such as crustification, symmetrical banding, and comb structures. These deposits are spatially associated with hot springs and geysers.

Epithermal deposits may consist of a wide variety of ores, such as Au, Au-Ag, Ag, Cu, Sn, Pb, Zn, Sb, U, and Hg.

For instance, epithermal gold deposits are said to be a type of lode deposit that contain concentrations of gold or silver and, sometimes, base metals, such as copper, lead, and zinc. As a lode deposit, the epithermal deposit is characterized by minerals that are either distributed throughout the ore-body, or contained in a system of veins.

Other characteristics that distinguish epithermal deposits are as follows:

  • Located near the surface, mineralization occurs at a maximum depth of 1 km (rarely deeper than 600m)
  • Form under moderate crustal temperatures of 50-300°C and under medium pressure
  • Commonly occur in island arcs and continental arcs associated with subduction
  • Also found in shallow marine environments
  • More susceptible to erosion, as they are shallow deposits

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