Cu porphyry
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Cu porphyry

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    Cu porphyry Cu porphyry Presentation Transcript

    • Porphyry Copper Deposits
    • What is a Porphyry? What is a Porphyry Copper Deposit?
    • Porphyry (por’phy-ry) An igneous rock of any composition that contains conspicuous phenocrysts in a fine-grained groundmass.
    •  
    • Porphyry
    • 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)
    • 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)
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    •  
    • Deposit Tonnage and Grade
    • Bajo la Alumbrera (Argentina)
    • Chuquicamata pit approximately 2x4x0.8km
    • Bingham Pit
    • La Escondida Chile
    • 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
    • World’s Leading Copper Producing Mines
    • World Copper Production/Consumption
    • Associated Metals
      • Molybdenum
      • Gold
      • Silver
      • Rhenium
    • 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
    • Are Porphyry Cu Deposits the Ideal Source for Copper?
    • Why not Sedimentary Base Metal Deposits?
    • Why not Sedimentary Base Metal Deposits? Part 2
    • Global Distribution of Porphyry Cu Deposits
    • Distribution in Time
    • Generalized Geology of a Porphyry Cu Deposit
    • Generalized Geology of a Porphyry Cu Deposit
    • Proposed Geology of Porphyry Mo Deposit
    • Geology of the San Manuel Kalamazoo Deposit
    • Geology of the Chuquicamata Deposit
    • Geology of the Bajo la Alumbrera
    • 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.
    • Alteration and Ore Zoning
    • Supergene Enrichment
    • Supergene Enrichment
    • Fluid Inclusions
    • More Fluid Inclusions
    • 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
    • Fluid Circulation Models
    • Hydrothermal Alteration
    • Mineral Stability
    • Stable Isotope Data
    • 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
    • Mineralization Environment
    • 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)
    • Tectonic Controls
    • Tectonic Control