Generic Model
- The source of metal and sulfur in VMS deposits is a combination of incompatible elements that are leached from footwall rocks in the sub-seafloor hydrothermal alteration zone by hydrothermal circulation. In some deposits magmatic fluids have been suggested to be an additional source of metals and fluids. Hydrothermal circulation is generally considered to be driven via heat in the crust often related to deep-seated igneous intrusions.
- Transport of metals occurs via convection of hydrothermal fluids, the heat for this supplied by the magma chamber and subvolcanic intrusions that lie below the volcanic edifice. Cool ocean water is drawn into the hydrothermal zone and is heated by the volcanic rock and is then expelled into the ocean, the process enriching the hydrothermal fluid in sulfur and metal ions.
- The ore materials are precipitated within a fumarole field or a black smoker field when they are expelled into the ocean, cool and mix with seawater resulting in the precipitation of sulfide minerals as stratiform sulfide ore. Some deposits show evidence of formation via deposition of sulfide via replacement of volcanosedimentary or sedimentary rocks, whereas others may also form by invasion of sulfur-rich brines into unconsolidated sediments.
Read more about this topic: Volcanogenic Massive Sulfide Ore Deposit
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