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Fumarole Deposit

Chemical Process (Vapor-phase Growth) - Ground Surface


Sublimation Deposit, Sublimate Deposit

Required Geological Setting

Island arc volcanoes, Intra-oceanic arc volcanoes


Minerals sublimated from volcanic gases near active fumaroles. Minerals are directly sublimated from volcanic gases or deposited by mixing volcanic gases with air. Gases lower than 400 degree are the source of such minerals as sassolite, sulphur, and sulfate minerals, whereas gases higher than 400 degree are the source of such minerals as halite, sylvite, hematite, magnetite, cristobalite, ilsemannite, wolframite, cassiterite, molybdenite, pyrite. Fumaroles of andesite magma may be the source of mafic silicate minerals such as forsterite, enstatite, hedenbergite, aegirine, and augite, which are not observed at fumaroles of rhyolite magma. It is well known that large amound of sulphur often observed as deposit near active fumaroles, and the formation process is considered as follows:

2H2S + 3O2 >> 2H2O + 2SO2

SO2 + 2H2S >> 3S + 2H2O

Fumarole Deposit

Distribution of fumarole deposits. Deposits align along continent-side (Eastern side) of the volcanic front. Green dots are localities of fumarole deposits described in this site. The yellow line is the volcanic front.

Reported Minerals

  • Sulphur
  • Alunogen
  • Jarosite
  • Alunite
  • Alum-(K)

Reported Minerals

  • Halite
  • Sylvite
  • Anglesite
  • Molybdite
  • Hematite
  • Magnetite
  • Cristobalite
  • Ilsemannite
  • Wolframite
  • Cassiterite
  • Molybdenite
  • Pyrite
  • Sphalerite


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