Transitional between magmatic and hydrothermal processes are ore deposits that form by reaction of magma with surrounding rock (skarn) or by reaction of a magma-derived hot hydrothermal fluid with surrounding rock (contactmetasomatic ores). These may be important carriers of Cu, Co, Mo, W, Zn, Pb, Ag and Au. Porphyry deposits form by the mixing of hot magmatic fluid carrying metals with meteoric water present in the upper crust.
