hydrothermal solution

A hydrothermal solution is hot, mineral-laden water that forms hydrothermal mineral deposits. These solutions typically originate from deep-circulating water heated by magma, radioactive decay, or faulting in the Earth's crust. They can deposit minerals by filling rock cavities or by replacing the rock itself, forming "replacement deposits."

For deposition to occur, hot water must be present to dissolve and transport minerals, interconnected openings must exist for the solution to flow, and sites for deposition are needed. Deposition is triggered by processes like boiling, temperature drops, mixing with cooler solutions, or chemical reactions with the surrounding rock. These solutions are often brines, effective at dissolving and transporting various ore minerals, including gold and silver. Hydrothermal solutions are common in Earth's crust, but the resulting mineral deposits are less so, often forming in restricted spaces or porous rocks. Deep-sea vents are an example where seawater circulates through hot volcanic rocks, precipitating mineral deposits rich in metals like iron, copper, and zinc.123