Hydrothermal mineral deposits

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Hydrothermal mineral deposits
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Hydrothermal Activity

• The circulation of water through hot volcanic
  rocks and magma
• Forms fumaroles volcanic vents emitting gases,
  some charged with dissolved minerals
• Forms geysers heated hydrothermal waters under
  pressure, that intermittently erupts at the
  surface
• Provides the source for Geothermal Energy.

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Hydrothermal Mineral Deposits
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• Most of the metallic minerals mined in the world,
  such as copper, gold, silver, lead, and zinc, are
  associated with volcanism
• Magmas may get the metallic components from
• Partial melting of the mantle at mid-ocean ridges
  and subduction zones
• From the subducted slab
• Melting of the crust as magma rises through it

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Image from the article The role of Magmas in the
formation of Hydrothermal Ore Deposits, by
Hendenquist and Lowenstern, Nature, Vol. 370,
1994
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• Rising magma does not always reach the surface to
  erupt instead it may slowly solidify beneath the
  volcano
• As the magma body cools, the metallic elements
  become concentrated in the residual fluids called
  HYDROTHERMAL SOLUTIONS
• Groundwater or seawater can also come in contact
  with the magma body and form hydrothermal
  solutions

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Water enters the ground by infiltration
Hydrothermal Systems
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Water enters the ground by infiltration
Hydrothermal Systems
Heated water begins to rise
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Water enters the ground by infiltration
Hydrothermal Systems
Hot Springs form when heated groundwater reaches
the surface
Heated water begins to rise
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Water enters the ground by infiltration
Hydrothermal Systems
Hot Springs form when heated groundwater reaches
the surface
Geysers form where a complicated plumbing system
allows steam pressure to be built up, causing
intermittent eruptions
Heated water begins to rise
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• The magma body heats and circulates the
  hydrothermal solutions carrying the metallic
  compounds
• The metals become concentrated by circulating hot
  fluids

When the fluids become cooler (near surface or
away from the magma body), the metallic minerals
are deposited to form rich mineral veins
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Oatman, AZ
Gold bearing hydrothermal vein deposit
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Large quantities of sulfide deposits form at
mid-ocean ridges and other undersea volcanoes in
this manner
Sulfides are the most common of the metallic
ores
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Some Copper Ores
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Kennecott Open Pit Copper Mine, Utah