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Cu porphyry

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  • 1. Porphyry Copper Deposits
  • 2. What is a Porphyry? What is a Porphyry Copper Deposit?
  • 3. Porphyry (por’phy-ry) An igneous rock of any composition that contains conspicuous phenocrysts in a fine-grained groundmass.
  • 4.  
  • 5. Porphyry
  • 6. Porphyry Copper Deposit A large low- to medium-grade deposit, of primarily of pyrite, chalcopyrite and molybdenite with characteristic concentric zoning of mineralization and alteration around calc-alkaline porphyritic intrusion (typically quartz monzonite to granodiorite)
  • 7. Typical Grades and Size
    • Copper grade is usually in the range of 0.5 to 1.0%. But can be as high as 1.5 or as low as 0.3%. The lower limit is defined by production costs.
    • Zones of local supergene enrichment can contain as much as 20% copper
    • Typically 1 to 2 square kilometers in size, but some deposits is in excess of 10 square kilometers. Mineralization has been found to continue to depths exceeding 1km.
    • The total amount of ore may be in excess of 3 billion tons (Chuquicamata)
  • 8.  
  • 9.  
  • 10. Deposit Tonnage and Grade
  • 11. Bajo la Alumbrera (Argentina)
  • 12. Chuquicamata pit approximately 2x4x0.8km
  • 13. Bingham Pit
  • 14. La Escondida Chile
  • 15. Importance of Porphyry CU Deposits
    • Porphyries produce approximately 60% of the worlds copper
    • In addition in conjunction with porphyry molybdenum deposits almost all of the world’s molybdenum is produced from porphyry deposits
    • Porphyry deposits produce a significant amount of the worlds silver and gold
  • 16. World’s Leading Copper Producing Mines
  • 17. World Copper Production/Consumption
  • 18. Associated Metals
    • Molybdenum
    • Gold
    • Silver
    • Rhenium
  • 19. Examples of Associated Metal Production
    • In addition to 320,000 tons copper, in the year 2000 Bingham also produced four million ounces of silver and about 500,000 ounces of gold and 21 million pounds of molybdenum
    • The Grasberg porphyry mine in Indonesia has an annual production of 1.5 billion pounds of copper and 2.5 million ounces of gold
    • Bajo la Alumbrera 2001 production was 674,000 oz of gold and 423 million pounds of copper
  • 20. Are Porphyry Cu Deposits the Ideal Source for Copper?
  • 21. Why not Sedimentary Base Metal Deposits?
  • 22. Why not Sedimentary Base Metal Deposits? Part 2
  • 23. Global Distribution of Porphyry Cu Deposits
  • 24. Distribution in Time
  • 25. Generalized Geology of a Porphyry Cu Deposit
  • 26. Generalized Geology of a Porphyry Cu Deposit
  • 27. Proposed Geology of Porphyry Mo Deposit
  • 28. Geology of the San Manuel Kalamazoo Deposit
  • 29. Geology of the Chuquicamata Deposit
  • 30. Geology of the Bajo la Alumbrera
  • 31. Alteration Zones - Lowell and Guilbert from core of porphyry stock outward
    • Potassic Alteration : Always present. Contains secondary k-feldspar, biotite and/or chlorite, replacing feldspar and plagioclase and mafics. May also contain serecite.
    • (Ore Zone)
    • Phyllic Zone : Often present. Characterized by vein quartz, sericite, pyrite and lesser amounts of chlorite and illite replacing k-feldspar and biotite.
    • Argillic Zone : Sometimes present. Characterized by montmorillonite and kaolinite replacing plagioclase and the replacement of biotite by chlorite.
    • Propylitic Zone : Always present and usually has the largest areal extent. Chlorite, calcite and edpidote replacing mafic minerals and to a lesser extent plagioclase.
  • 32. Alteration and Ore Zoning
  • 33. Supergene Enrichment
  • 34. Supergene Enrichment
  • 35. Fluid Inclusions
  • 36. More Fluid Inclusions
  • 37. Fluid Inclusion Findings
    • Fluid inclusion data suggests a two end-member system with mixing
    • Magmatic fluid inclusions have very high salinities (30 to 60 wt % NaCl equivalent) and very high homogenization temperatures
    • Meteoric fluids have lower salinities (<15 wt % NaCl equivalent) and much lower homogenization temperatures
  • 38. Fluid Circulation Models
  • 39. Hydrothermal Alteration
  • 40. Mineral Stability
  • 41. Stable Isotope Data
  • 42. What do Stable Isotopes Suggest
    • Hydrothermal alteration (and most likely metal transport) is the result rock interaction with both magmatic and meteoric water
    • Early potassic alteration is most likely the result of rock interaction with magmatic water
    • Later quartz-serecite alteration was caused by meteoric water
  • 43. Mineralization Environment
  • 44. Radiogenic Isotopes
    • Most Porphyry Cu intrusives often have low 87 Sr/ 86 Sr ratios on the order of 0.703 to 0705 - this is unlike tin and moly porphyries that have much higher Sr ratios.
    • Intrusive biotite is usually low in fluorine
    • These as well factors as well as the geologic setting point to mantle derived sources for the intrusives - unlike Tin and Moly porphyries which seem to have a much larger crustal component (s-type granites)
  • 45. Tectonic Controls
  • 46. Tectonic Control