Sulfides: major ore minerals on earth - very diverse group

• anions: S, Se, Te, As, Sb, Bi
  note that Se, Te, As, Sb, and Bi can also act as cations
  => resulting compound is a sulfosalt

• cations: Fe, Cu, Zn, Ni, Co, Mn
  
  minor: Ag, Cd, Sn, Pt, Hg, Tl, Pb, Bi

• Common occurrences:
  1. Associated with volcanic activity and hot springs

  2. ** Hydrothermal vein deposits (may be associated with continental rifting)
     

     Classification system (Lindgren)
     3 Types of Hydrothermal Deposits:

     1. Epithermal deposits:
        - relatively low temperature solution when precipitation occurs
        (50-200^oC)

        - pressure: moderate to low => not too deep

        - common minerals:

        ORES: stibnite (Sb), cinnabar (Hg), silver & silver
        sulfides, gold
        
        GANGUE: quartz, chalcedony, opal, calcite, aragonite,
        dolomite, fluorite

     2. Mesothermal deposits:
        - moderate temperatures: 200-300^oC

        - pressure: moderate to high - deeper in crust

        - common minerals:

        ORES: sulfides of Fe, Pb, Zn, Cu, & gold veins

        GANGUE: quartz, calcite, rhodochrosite, siderite

     3. Hypothermal deposits:
        - high temperatures: 300-500^oC

        - pressure: moderate to high

        - common minerals:

        ORES: cassiterite (Sn), scheelite & wolframite (W),
        molybdenite (Mo)

        GANGUE: quartz, tourmaline, topaz,

        other high temp silicates

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     Supergene Enrichment

     *veins undergo a secondary enrichment - become more concentrated in ores