GOSSAN FORMATION AND SUPERGENE ENRICHMENT
Reaction Equations
1. 2FeS2 + 15/2O2 + 4H2O Fe2O3 + 4SO42- +8H+
Pyrite
Sulphuric acid enhances the breakdown of accompanying sulphides:
2. 2 CuFeS2 +17/2O2 +2H2O ---> Fe2O3 +2Cu2+ + 4 SO42- + 4H+
Chalcopyrite
Copper is leached downwards and may reprecipitate as Cu sulphates (or carbonates)
above the water table or copper sulphides (esp. chalcocite Cu2S) below the water table
(by replacement of pyrite). This can result in substantial increase in metal content.
Reaction Equations
1. 2FeS2 + 15/2O2 + 4H2O Fe2O3 + 4SO42- +8H+
Pyrite
Sulphuric acid enhances the breakdown of accompanying sulphides:
2. 2 CuFeS2 +17/2O2 +2H2O ---> Fe2O3 +2Cu2+ + 4 SO42- + 4H+
Chalcopyrite
Copper is leached downwards and may reprecipitate as Cu sulphates (or carbonates)
above the water table or copper sulphides (esp. chalcocite Cu2S) below the water table
(by replacement of pyrite). This can result in substantial increase in metal content.
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