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What is a porphyry copper deposit?

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A periodic table element box for copper shows its symbol Cu, atomic number 29, atomic weight 63.546, electron configuration, and name. Icons indicate copper is a solid, weakly basic transition metal with face-centered cubic crystal structure. A key explains the symbols and color coding. — copper Properties of copper.

A porphyry copper deposit is a large, low-grade body of rock characterized by disseminated copper minerals, such as chalcopyrite and bornite.12

These deposits are formed within the fractured periphery of porphyritic igneous rocks, such as diorite or quartz monzonite. The shattered rock acts as a permeable medium for hydrothermal solutions, which deposit minerals in a network of tiny quartz veins.12

Although these deposits typically contain only 0.5 to 1.5 percent copper by weight, they are economically significant because they contain massive tonnages of ore that can be extracted on a large scale at a low cost. Consequently, porphyry copper deposits are the source of more than 50 percent of the world's copper production. They are frequently found near stratovolcanoes, particularly along the borders of the Pacific Ocean basin, including major sites in Chile and the United States.12