GEOL 11040 Lecture Notes - Lecture 29: Road Salt, Magma Chamber, Crystallization
30 Nov 2018
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Document Summary
Metallic resources often come in the form of ores. Ore: rock composed of metal rich minerals. Can all become concentrated in their pure form. Geological processes form ores when they remobilize disseminated minerals and replace them in a more concentrated form. Fractional crystallization in a large and slowly cooling magma chamber can create layers of pure and economically important minerals. Other ores can form under different conditions. Hot and molten rock drives hydrothermal circulation. Hot fluid pulls metal ions from rock near an intrusion. Precipitates ions where there are changes in pressure, temperature, or oxygenation. Result of mineral precipitation as hot water exits vents on the seabed/lakebed. Thousands of years of this leads to a build up of ores. Groundwater flow is colder and slower than hydrothermal but can still pull metals from rocks and move them to the surface through reprecipitation. Secondary ore enrichment : concentration of pre-existing ores by leaching (pulling out) and reprecipitation.
