How do skarn deposits form when hot fluids enter limestone or marble?

Skarn deposits form when high-temperature, hydrothermal solutions—typically originating from nearby magma chambers—invade carbonate-rich rocks like limestone or marble.1

The process involves a strong chemical reaction between the slightly acidic hydrothermal fluids and the carbonate minerals calcite and dolomite. During this interaction, the fluids introduce elements such as silica, iron, aluminum, and magnesium into the parent rock. These elements combine with the calcium and magnesium already present in the limestone or marble to create new silicate minerals, such as diopside, tremolite, and andradite garnet.12

As this wave of metamorphism progresses, the hydrothermal solutions may also deposit valuable ore minerals, including iron, copper, zinc, tungsten, or molybdenum. Because these deposits are closely associated with igneous intrusions, they are frequently found in the contact zones surrounding these rock bodies.12