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Porphyry Deposits

  1. Economic Definition of Porphyry Deposits: These are deposits with a copper grade of approximately 0.1-2%, and reserves exceeding 50 million tons, containing small amounts of Mo, Au-Ag. They can be exploited through open-pit or underground mining methods.

  2. Geological Definition of Porphyry Deposits: These deposits are characterized by cutting rocks of various ages and types. They are shallowly emplaced, acid to intermediate in composition, with a porphyritic texture. They are formed within and/or around altered plutonic rocks, genetically related to intrusive rocks. The deposits are characterized by disseminated, veinlet, and stockwork-type primary mineralization in these rocks

  • The first porphyry-type deposit was exploited in the 1920s.

  • Porphyry deposits are associated with intrusive rocks that have a porphyritic texture.

  • The abundance of ore is a key factor for mining operations.

  • Copper deposits associated with porphyritic intrusives are referred to as copper porphyries.

  • Copper (Cu) and Molybdenum (Mo) form as very large ore bodies; 50-x00 million tonnes.

  • Tin (Sn) is much less; 2-10 million tonnes.

  1. Porphyry Cu: contains Mo, Au-Ag.

  2. Porphyry Mo (Climax): contains Sn, W, Pyrite.

  3. Porphyry Sn: contains W, Mo, Bi, Fluorine.

  • All three types of metal deposits are considered significant with their by-products.

  • Porphyry Cu deposits account for more than 50% of the annual global copper production and many deposits are in production.

  • Porphyry Mo production covers more than 70% of the global molybdenum production.

  • Porphyry Sn is of less importance. The majority of tin production is obtained from vein-type and placer deposits. Characteristics of the Main Intrusions:

  • Acid plutonic rocks of the granite family vary from Granodiorite to Tonalite, Quartz Monzonite to Diorite.

  • Type I granitoids.

  • Intrusions arising in island arc areas show initial primary Sr isotope ratios of 0.705-0.702, and the ore is thought to derive from the upper mantle or oceanic crust cycle.

  • Intrusions formed in continental areas indicate derivation from contamination with crustal material.

  • Multistage intrusions are common, with mineralization occurring in the later stages.

  • Copper (Cu) Deposits: occur in rocks varying from Granodiorite to Tonalite, and from Diorite to Quartz Monzodiorite.

  • Molybdenum (Mo) Deposits: are found in rocks with granodiorite-Quartz Monzonite composition.

  • Tin (Sn) Deposits: are in felsic intrusive rocks (rich in F and B).

  • Tungsten (W) Deposits: are in felsic intrusions (rich in F).

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