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Porphyry deposits.ppt

  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 Deposit, Indonesia Goethite-coated quartz veins cutting sericite-altered diorite Tonalite porphyry
  6. Hydrothermal Alteration at Batu Hijau
  7. Batu Hijau Porphyry Cu-Au Ores Supergene Hypogene Chalcopyrite Bornite Malachite
  8. Spatial Distribution of Porphyry Deposits
  9. The Origin of Porphyry Cu-Au-Mo Magmas Hydration Melting
  10. Porphyry-epithermal-skarn system - overview
  11. Idealized Porphyry Alteration/Mineralization (Lowell and Gilbert, 1970)
  12. Schematic Porphyry-Epithermal Alteration Sillitoe (2010)
  13. Potassic Alteration High Grade Ore Bornite Chalcopyrite Porphyry Ore and Alteration Textures Phyllic Alteration
  14. Potassic Alteration Revealed by Staining
  15. 3KAlSi3O8 + 2H+ = KAl3Si3O10(OH)2 + 6SiO2 + 2K+ K-feldspar Muscovite Quartz Hydrothermal Alteration – Chemical Controls 2KAl3Si3O10(OH)2 + 2H+ + 3H2O = 3Al2Si2O5(OH)4 + 2K+ Muscovite Kaolinite
  16. Metal Zonation in Porphyry Systems Bingham Mineral Park
  17. Tectonic Setting of Porphyry Deposits
  18. Porphyry metal associations as a function of intrusive composition
  19. LV inclusions VL inclusions LVHS inclusions Fluid Inclusions in Porphyry Ore Depositing Systems Aqueous-carbonic Fluid inclusion
  20. 100 mm Primary, Pseudosecondary and Secondary Fluid Inclusions Primary and pseudosecondary fluid inclusions in dolomite
  21. Isochores for Fluid Inclusions in the System H2O
  22. Fluid Inclusion Microthermometry
  23. Microthermometry of Aqueous Fluid Inclusions
  24. Isochores for Halite-bearing inclusions
  25. Isochores for the System NaCl-H2O
  26. Salinity Determination from Halite Dissolution
  27. Salinity Determination from Ice Melting
  28. P-T-X Relationships in the System NaCl-H2O
  29. 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)
  30. Laser Ablation ICP-MS and Fluid inclusions
  31. Stable Isotope Data for Porphyry Deposits
  32. Porphyry-Epithermal System Evolution
  33. Chemical Controls on Ore Formation CuClo +FeCl2 o + 2H2S + 0.5O2= CuFeS2 + 3H+ + 3Cl- + 0.5H2O Deposition of Chalcopyrite (CuFeS2) Deposition favoured by an increase in f O2, an increase in f H2S and an increase in pH What about temperature?
  34. Decreasing Temperature – the Main Control on Porphyry Copper Ore Formation? (Hezarkhani and Williams-Jones, 1998) Modelling ore deposition in the Sungun porphyry, Iran. Solubility of chalcopyrite in a 1 m NaCl solution. Copper solubility drops to ~ 4,000 ppm at 400 oC, the temperature of ore formation and 1 ppm at 300 oC
  35. Decreasing Temperature – the Main Control on Porphyry Copper Ore Formation (Landtwing et al., 2005) Copper concentrations in fluuid inclusions of the Bingham porphyry, USA
  36. Cu-Mo Zoning in Porphyry Systems Porphyry Cu-Mo deposits are commonly zoned with a deeper, higher temperature molybdenite-rich zone and a shallower, lower temperature chalcopyrite-rich zone. Cooling of an aqueous fluid initially containing 2 m NaCl, 0.5 m KCl, 4000 ppm Cu and 1000 ppm Mo in equilibrium with K-feldspar, muscovite and quartz.
  37. Magma Emplacement, and the Nature of the Exsolved Fluid 0.01 0.1 1 10 100 0 500 1000 1500 0 1.5 3.0 4.5 Vapour Liquid 600C 800C Halite H2O-NaCl V V L L H Magmatic fluid Pressure (bar) Depth (Km) Fluid inclusions NaCl wt.%
  38. Transport of Metals by Vapour? Extinct fumarole Summit of Merapi volcano, Indonesia Fumarole emitting magmatic gases at 600 oC Mo3O8.nH2O Ilsemanite
  39. Quartz monz onite porphyry E quigranular monz onite > 0 . 7 % C u > 0 . 7 % C u > 0 . 3 5 % C u > 0 . 3 5 % Cu > 0 . 3 5 % C u < 0.35% Cu S edimentary R ocks upper lim it of critical-type inclus ions 1 - 5 v o l . % q u a r t z v e i n s 1 - 5 v o l. % q u a rt z v e i n s < 1 vol % quartz veins 5-10 vol. % quartz veins brine inclusions critical-type inclusions vapor-rich inclusions 2.5 3.0 3.5 2.0 P aleo-depth (k m) NNW halite opaq ue va por va por va por va por sylvite liq uid liq uid liq uid chalc opyrite 10 mm 10 mm 10 mm hema tite 1997 Pit SS E The Bingham Porphyry Deposit - A Case for the Vapour Transport of Copper (Williams-Jones and Heinrich, 2005)
  40. The Solubility of Chalcopyrite in Water Vapour Increasing PH2O promotes hydration (and solubility) and increasing temperature inhibits hydration. Migdisov et al. (2014)
  41. From Hypogene to Supergene Supergene Hypogene Chalcopyrite Bornite Malachite
  42. Oxidised zone Primary zone Enriched zone Leached zone Mineralized gravel Mineralized bedrock Barren gravel Supergene enrichment FeS2 + H2O + 7/2O2= Fe2+ + 2SO4 2- + 2H+ 2Fe2+ + 2H2O + 1/2O2 = Fe2O3 + 4H+; 2Cu+ + H2O = Cu2O + 2H+ 2Cu+ + SO4 2- = Cu2S + 4O2 Leached zone – acidity creation CuFeS2 + 4O2= Fe2+ + Cu2+ + 2SO4 2- Oxidised zone – Fe and Cu oxides, acidity creation Enriched zone – reduction and sulphide deposition
  43. Cu2+ Malachite Cu2(OH)2CO3 Eh pH Supergene enrichment
  44. References 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. 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. Sillitoe, R.H., 2010, Porphyry copper systems: Econ. Geol., 195, 3-41.