Types of Porphyry Copper Systems

 

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Types of Porphyry Systems

Porphyry copper systems can be subdivided based on their metal contents (especially Cu, Au, Mo) and their host-igneous characteristics. According to USGS and economic geology studies:

1. Cu-Au Porphyries

   • These are gold-rich porphyry systems. One classification (Cox & Singer, 1992) defines “Cu-Au” porphyries when the ratio of Au/Mo (gold to molybdenum) is ≥ 30.

   • They often form in arc-related or island-arc settings.

   • Ore minerals: chalcopyrite, bornite, sometimes electrum or tellurides; associated minerals include native gold, etc. 

2. Cu-Mo Porphyries

   • These have a low ratio of Au/Mo (≤ 3) per the Cox & Singer scheme.

   • Molybdenum (as molybdenite) is a major product.

   • By-products often include rhenium (Re), silver, and other trace elements. 

3. Intermediate / Mixed Types (Cu-Au-Mo)

   • When the Au/Mo ratio falls between the extremes (e.g., 3–30), you get mixed types with significant amounts of both Au and Mo. 

4. Other Related Porphyries

   • There are also porphyry Mo-only deposits, and even W-Mo (tungsten-molybdenum) porphyries.

   • Some “skarn-related porphyry” systems exist, though more difficult to classify.

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Major Examples of Porphyry Copper Systems

Here are some well-known porphyry deposits, with different types and geological significance:

• Bingham Canyon (Utah, USA)

  • One of the largest porphyry copper mines. 

  • Its geology shows distinct metal zoning: a bornite-/chalcopyrite-­rich higher-grade copper zone, a molybdenite (Mo) zone, then pyrite, etc. 

  • This deposit has both copper and molybdenum.

• Grasberg (Indonesia)

  • A very large Cu-Au porphyry system.

  • High gold content makes it economically very important.

• Chuquicamata (Chile)

  • One of the biggest porphyry copper deposits in the world. 

  • Typical of large-scale Cu-Mo porphyry systems in subduction-related arcs. 

• Escondida (Chile)

  • A supergiant porphyry deposit. 

  • Primarily Cu-Mo, with very large production capacity. 

• Skouries (Greece)

  • A gold-copper porphyry deposit.

  • Multiple intrusive phases and strong potassic alteration. 

• Majdanpek (Serbia)

  • Porphyry Cu-Au system. 

  • Very significant reserves of both copper and gold.

• Sungun (Iran)

  • A large porphyry copper deposit in Iran. 

  • Good example of how porphyry systems can be distributed outside the most famous “belts.”

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Why These Examples Matter

• These cases illustrate how porphyry systems vary: some are copper + gold, others are copper + molybdenum, and some even have all three.

• The geological setting (plate tectonics, depth of intrusion, multiple intrusive phases) helps determine what type of porphyry deposit develops.

• From an exploration standpoint, knowing what subtype you are dealing with helps vector toward the highest-value part of the deposit (e.g., toward the potassic core for Cu-Au).

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