Eluvium

Eluvium

[ih-loo-vee-uhm]
In geology, eluvium or eluvial deposits are those geological deposits and soils that are derived by in situ weathering or weathering plus gravitational movement or accumulation.

The process of removal of materials from geological or soil horizons is called eluviation. There is a difference in the usage of this term in geology and soil science. In soil science, eluviation is the transport of soil material from upper layers of soil to lower levels by downward precipitation of water across soil horizons, and accumulation of this material (illuvial deposit) in lower levels is called illuviation. In geology, the removed material is irrelevant, and the deposit (eluvial deposit) is the remaining material.

Eluvial ore deposits are those such as tungsten and gold placer deposits formed by settling and enriched by the winnowing or removal of lower density materials. Diamonds within yellow ground (weathered portions of kimberlites) may be considered to be eluvial deposits. Cassiterite and columbite-tantalite deposits also occur as residual or eluvial concentrations. The Pitinga tin deposit in Brazil, an eluvial deposit, is one of the largest tin mines in the world. Weathering supergene enrichment of an apatite rich carbonatite in Ontario has produced a significant eluvial phosphate ore deposit.

References

  • Gupta, Chiranjib Kumar (2002) Chemical Metallurgy: Principles and Practice, Wiley, ISBN 3-527-30376-6
  • Cronan, David Spencer (1999) Handbook of Marine Mineral Deposits, CRC Press, ISBN 0-8493-8429-X
  • Swiecki, Rafal (2006) Eluvial Placers Accessed 18 April 2006
  • Van Hees, Edmond H., (2002) SUPERGENE PHOSPHATE ENRICHMENT IN CARBONATITE-DERIVED ELUVIAL SEDIMENTS: AGRIUM PHOSPHATE MINE, KAPUSKASING, ONTARIO, CANADA, The Geological Society of America (GSA) abstract. Accessed 18 April 2006

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