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Hydrothermal mineral deposits. Hydrothermal Activity. The circulation of water through hot volcanic rocks and magma Forms fumaroles – volcanic vents emitting gases, some charged with dissolved minerals
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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 forGeothermal Energy.
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
Image from the article: The role of Magmas in the formation of Hydrothermal Ore Deposits, by Hendenquist and Lowenstern, Nature, Vol. 370, 1994
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
Water enters the ground by infiltration Hydrothermal Systems
Water enters the ground by infiltration Hydrothermal Systems Heated water begins to rise
Water enters the ground by infiltration Hydrothermal Systems Hot Springs: form when heated groundwater reaches the surface Heated water begins to rise
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
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
Oatman, AZ Gold bearing hydrothermal vein deposit
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