How can geothermal systems form deposits of gold, silver, and other minerals?

Geothermal systems act as natural underground distilleries that facilitate the formation of hydrothermal mineral deposits, including gold and silver. This process occurs through the following mechanisms:

• Dissolution: Deeply circulating groundwater is heated by nearby magma, creating a hot, mineral-laden solution. As this fluid circulates through the subsurface, it dissolves trace amounts of rare elements, such as gold and silver, from the surrounding host rocks.12
• Transport: The heated solution moves through interconnected openings, such as fracture zones or porous aquifers, driven by convection.123
• Precipitation: When the solution encounters conditions that favor deposition—such as a drop in temperature, boiling, or chemical reactions with surrounding rock—the dissolved minerals precipitate out of the solution.12

These minerals often accumulate in open fissures to form veins or replace existing rock to create replacement deposits. Deposits formed at shallow depths near boiling hot springs are specifically known as epithermal deposits, which are frequently associated with high concentrations of precious metals.4