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Porphyry Deposits

Porphyry Deposits. The Importance of Porphyry Deposits as a Copper and Gold Resource. Gold Resources. Copper Resources. A Geological Cross Section through the Batu Hijau Porphyry Deposit, Indonesia. (920 million tons of ore grading 0.55 wt.% Cu, 0.42 g/t Au).

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Porphyry Deposits

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  1. Porphyry Deposits

  2. The Importance of Porphyry Deposits as a Copper and Gold Resource Gold Resources Copper Resources

  3. A Geological Cross Section through the Batu Hijau Porphyry Deposit, Indonesia (920 million tons of ore grading 0.55 wt.% Cu, 0.42 g/t Au)

  4. Batu Hijau Porphyry Cu-Au Deposit, Indonesia

  5. Batu Hijau Porphyry Cu-Au Ores Hypogene Supergene Malachite Bornite Chalcopyrite

  6. Spatial Distribution of Porphyry Deposits

  7. The Origin of Porphyry Cu-Au-Mo Magmas Hydration Melting

  8. Porphyry-epithermal-skarn system - overview

  9. Idealized Porphyry Alteration/Mineralization (Lowell and Gilbert, 1970)

  10. Bornite Chalcopyrite High Grade Ore Potassic Alteration Porphyry Ore and Alteration Textures Phyllic Alteration

  11. Potassic Alteration Revealed by Staining

  12. Tectonic Setting of Porphyry Deposits

  13. Porphyry metal associations as a function of intrusive composition

  14. Fluid Overpressure and Porphyry Ore Formation

  15. Porphyry deposit fundamentals Potassic alteration K-feldspar Comb quartz Aplite Fine-grained porphyry

  16. Hydrothermal Alteration – Chemical Controls 3KAlSi3O8 + 2H+ = KAl3Si3O10(OH)2 + 6SiO2 + 2K+ K-feldspar Quartz Muscovite 2KAl3Si3O10(OH)2 + 2H+ + 3H2O = 3Al2Si2O5(OH)4 + 2K+ Muscovite Kaolinite

  17. LV inclusions Fluid Inclusions in Porphyry Ore Depositing Systems VL inclusions LVHS inclusions Aqueous-carbonic Fluid inclusion

  18. 100 mm Primary, Pseudosecondary and Secondary Fluid Inclusions Primary and pseudosecondary fluid inclusions in dolomite

  19. Fluid Inclusion Microthermometry

  20. Freezing of Aqueous-Carbonic Fluid Inclusions

  21. Homogenization of Aqueous-Carbonic Inclusions

  22. Salinity Determination from Ice Melting

  23. Salinity Determination from Halite Dissolution

  24. Isochores for Fluid Inclusions in the System H2O

  25. Isochores for Halite-bearing inclusions

  26. Isochores for the System NaCl-H2O

  27. P-T-X Relationships in the System NaCl-H2O

  28. Salinity-Temperature Relationships in Porphyry Systems Note existence of high temperature VL and LVS inclusions. Evidence of boiling or condensation? Data from the Sungun Cu-Mo porphyry, Iran (Hezarkhani and Williams-Jones, 1997)

  29. Laser Ablation ICP-MS and Fluid inclusions

  30. Stable Isotope Data for Porphyry Deposits

  31. Chemical Controls on Ore Formation Deposition of Chalcopyrite (CuFeS2) CuClo +FeCl2o + 2H2S + 0.5O2= CuFeS2 + 3H+ + 3Cl- + 0.5H2O Deposition favoured by an increase in f O2, an increase in f H2S and an increase in pH What about temperature?

  32. Decreasing Temperature – the Main Control on Porphyry Copper Ore Formation

  33. Summit of Merapi volcano, Indonesia Transport of Metals by Vapour? Fumarole emitting magmatic gases at 600 oC Extinct fumarole Ilsemanite Mo3O8.nH2O

  34. Magma Emplacement, and the Nature of the Exsolved Fluid

  35. The Bingham Porphyry Deposit - A Case for the Vapour Transport of Copper (Williams-Jones and Heinrich, 2005)

  36. A Model for the Formation of Porphyry Deposits

  37. Supergene enrichment Leached zone Mineralized gravel Oxidised zone Barren gravel Enriched zone Primary zone Mineralized bedrock Leached zone – acidity creation FeS2 + H2O + 7/2O2= Fe2+ + 2SO42- + 2H+ CuFeS2 + 4O2= Fe2+ + Cu2+ + 2SO42- Oxidised zone – Fe and Cu oxides, acidity creation 2Fe2+ + 2H2O + 1/2O2 = Fe2O3 + 4H+; 2Cu+ + H2O = Cu2O + 2H+ Supergene zone – reduction and sulphide deposition 2Cu+ + SO42- = Cu2S+ 4O2

  38. Supergene enrichment O2 H2O Cu2+ Malachite Cu2(OH)2CO3 Covellite Cuprite Cu2O Eh Native Cu H2O H2 Chalcocite pH

  39. References Evans, A.M., 1993, Ore geology and industrial minerals, an introduction: Blackwell Science, Chapter 14. Pirajno, F. 2009, Hydrothermal processes and mineral systems, Springer, Chapter 5. Seedorff, E., Dilles, J.H., Proffett Jr, J.M., Einaudi, M.T., Zurcher, L., Stavast, W.J.A, 2006, Porphyry Deposits: Characteristics and origin of hypogene features in Hedenquist et Al. (eds) Economic Geology One Hundreth Anniversary Volume, p.251-298. Williams-Jones, A.E. and Heinrich, C.H., 2005, Vapor transport of metals and the formation of magmatic-hydrothermal ore deposits: Econ. Geol., 100, p.1287-1312.

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