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Bog Iron Deposit


Required Geological Setting

Island arc volcanoes


Limonite deposits precipitated from the hot spring water. Goethite and jarosite deposit from pH 2.5-3.0 strong acidic hot spring water rich in Fe and SO4. Jarosite precipitates near hot spring bents where the hot spring water is more acidic, and goethite precipitates in the down reaches where the hot spring water is less acidic. It is considered that Fe ions in the hot springs was deposited as goethite by the activity of Fe bacteria in the hot spring water. Some reports suggest that Fe hydroxides such as schwertmannite formed as precursor, and such Fe hydroxides change to more stable goethite afterwards. Limonite ores often produce impression fossils of mosses, leaves, or plant branches. Limonite ores may be associated with diatomite and/or various phosphate minerals.

Bog Iron Deposit

Distribution of Bog Iron Deposits described in this site. Deposits align along continent-side (Eastern side) of the volcanic front. The yellow line is the volcanic front.

Reported Minerals

  • Goethite
  • Jarosite
  • Hematite
  • Schwertmannite
  • Diatomite


Related Occurrences

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