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2011-04-13 15:14:09
ASBOG Study Guide Chap Six

ASBOG Study Guide Chapter 6 - Economic Geology
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  1. Alteration
    Any change in the mineral compositoin of a rock caused by pohyscial or chemical means, espcially by hydrothermal fluids
  2. Assay
    An analysis of the proportions of metal in an ore. Composition, purity, weight, or other properties of economic interested are tested
  3. Average Grade
    The average quantity or percentage of ore minearl content in an ore body

    • Gavg = Sums (width of ore vein x assay)
    • Sums (widths of ore veins)
  4. Base Metal
    a common and chemically acitve metal - lead or copper for example
  5. Density
    The mass or weight of a substance per volume that it occupies
  6. Dolomitization
    The process by which limestone is converted to dolomite by the replacement of calcium carbonate by magnesium carbonate
  7. Eh
    Oxidation potential; the potential of a half-cell, measured against the standard hydrogen half-cell
  8. Epigenetic
    An ore deposit that originates later that the enclosing host rocks
  9. Exhalite
    The chemical product of exhalation; a deposit formed by the interaction of volcanically derived water and sea water with subjacent rocks
  10. Gangue
    Valuless rock or mineral aggregates in an ore; economically undesirable
  11. Giant field
    A peroleum field containing 500 million barrels or more of recoverable oil; a nautral gas field which has a minimum of 3.5 trillion ft3 of recoverable gas
  12. Gossan
    An iron-bearing weathered product overlying a sulfide deposit
  13. Hydrothermal
    Pertaining to hot water, the action of hot water, or the products of hot water
  14. Metasomatism
    The process of practically simultaneous solution and deposition of a new mineral in an old mineral by means of interstitial fluids
  15. pH
    The negative log10 of the hydrogen-ion activity in a solution, a measure of the acidity or basicity of a solution
  16. Porphyry
    An igneous rock that contains phenocrysts in a fine grained matrix
  17. Pyritization
    Introduction of, or replacement by, pyrite, a common process of hydrothermal alteration
  18. Rank
    The degree of progressive meatmorphism of peat (coalification)
  19. Skarn
    Silicate rocks of complex metamorphic-metasomatic mineralogy formed in carbonate rocks in a contact metamorphic aureole
  20. Stoping
    Extraction of ore in an underground mine by working laterally in a series of levels in the plane of the vein
  21. Supergene Enrichment
    A near-surface process of mineral deposition in which metals are leached by acidic solutions, carried downward, and repreciptated, enriching the sulfide minerals already present
  22. Syngenetic
    A mineral deposit formed contemporaneously wit, and by the same processes as, the enclosing rocks