Where porphyry copper deposits are found

The worldwide distribution of porphyry deposits is controlled by orogenic belts. Two types of orogenic belts are known to host porphyry deposits; those created along a subduction zone (where a continental and ocean plate meet) and those found along island arcs where two oceanic plates collide.

The porphyry deposits along the coast of South America, and North America are an example of porphyry deposits formed along a subduction zone. Those in the Philippines and Papua New Guinea are examples of island arc porphyry deposits.

Examples of porphyry copper deposits include Codelco’s Salvador mine and its giant Chuquicamata deposit in Chile, which is the world's second deepest open pit mine. The only one that's deeper is the Bingham copper porphyry mine in Utah, US operated by Rio Tinto’s (NYSE:RIO, ASX:RIO, LSE:RIO) subsidiary Kennecott.

Different types of porphyry copper deposits

In porphyry copper deposits, copper grades can range from 0.2 percent to more than one percent, while molybdenum grades can range from approximately 0.005 percent to 0.03 percent. Silver grades range from 0.004 to 0.35 grams per metric ton, and gold grades range from 0.2 to 5 grams per metric ton.

There are a limited amount of copper-porphyry deposits in the world. However, one prime example is Freeport McMoRan’s (NYSE:FCX) Grasberg mine in Indonesia, the largest gold mine and one of the largest copper mines in the world.

The future of porphyry copper deposits

Exploration companies are always in search of the next great copper porphyry deposit. Not only are these deposits an excellent source for copper, but as mentioned above, they often feature significant co- and by-products, which can help lower production costs. What’s more, porphyry deposits are amenable to open-pit mining, often a lower-cost method of resource extraction.