Skarn

A coarse grained metamorphic rock that forms by the replacement of carbonate rocks such as limestone or dolomite during regional or contact metamorphism combined with metasomatism, the chemical alteration of rock by circulating fluids. It develops through several related processes, including metamorphic recrystallization, reactions between adjacent rock layers, and infiltration by magmatic-hydrothermal fluids, and it is dominated by garnet and pyroxene along with other calc-silicate minerals rich in calcium, magnesium, iron, manganese and aluminum. Skarns commonly form where a granitic intrusion has come into contact with carbonate rock along a fault or shear zone, in high temperature settings that can occur near oceanic island arcs, continental margins or shallow geothermal systems, with the exact mineral suite depending on the composition of the original rock. Because skarn deposits are commonly enriched in metals such as copper, tungsten, iron, tin, molybdenum, zinc, lead and gold, they are an economically important source of ore.