Authigenesis

Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed. Such deposits are described as authigenic. Authigenic sedimentary minerals form during sedimentation by precipitation or recrystallization[1] instead of being transported from elsewhere (allogenic) by water or wind.[2] Authigenic sediments are the main constituents of deep sea sedimentation. Authigenic clays tend to reduce the porosity of sediments, thus reducing permeability.

Authigenic minerals in marine sediment

In metamorphic petrology an authigenic mineral is one formed in situ during metamorphism, again by precipitation from fluids or recrystallization.

For any mineral to be precipitated, the water must be oversaturated with respect to that mineral. For calcite, this means that the area of deposition must be above the carbonate compensation depth, or that the pore waters are sufficiently saturated due to dissolution of other grains that precipitation can begin. The alkalinity can also be reduced by microbial sulphate reduction.[3]

Common authigenic minerals in sedimentary rocks

Authigenic glauconite from Dorset, England
gollark: Unless I can *somehow* make this use a different NN backend without beeing utterly.
gollark: On an unrelated note, I am cancelling all efforts to develop a less slow ++experimental_qa because it is too irritating.
gollark: Ah, applied principle of explosion.
gollark: And both seem like a reasonable response to "people will be eternally tortured if they do not do this".
gollark: I don't *agree* with religious evangelism, I'm saying that it does not seem inconsistent with "true Catholicism" as qh4os says.

See also

Neomorphism

References

  1. Authigenic from Oilfield Glossary
  2. Allogenic from Oilfield Glossary
  3. SCOTT RITGER, BOBB CARSON and ERWIN SUESS, 1987. Methane-derived authigenic carbonates formed by subduction-induced pore-water expulsion along the Oregon/Washington margin. Geol. Soc.Am. Bull.; 98; 147-156
  4. SCOTT RITGER, BOBB CARSON and ERWIN SUESS, 1987. Methane-derived authigenic carbonates formed by subduction-induced pore-water expulsion along the Oregon/Washington margin. Geol. Soc.Am. Bull.; 98; 147-156
  5. Kathleen C. Ruttenberg and Robert A. Berner, 1993. Authigenic apatite formation and burial in sediments from non-upwelling, continental margin environments. Geochim. Cosmochim. Acta.; 57; 991-1007
  6. M. D. Wilson and E. D. Pittman, 1977. Authigenic clays in sandstones; recognition and influence on reservoir properties and paleoenvironmental analysis. J. Sed. Res.; 47; 3-31.
  7. Collinson, J.D. and Thompson, D.B. (1982). Sedimentary Structures. London: George Allen & Unwin. p. 151. ISBN 0-04-552018-6.CS1 maint: multiple names: authors list (link)
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.