Detachment fault

Source: Wikipedia, the free encyclopedia.
Doso Doyabi, Snake Range, Nevada
, which was formed by detachment faulting.

A detachment fault is a gently

isostatic effects of tectonic denudation
. They may also be called denudation faults. Examples of detachment faulting include:

Detachment faults have been found on the sea floor close to divergent plate boundaries characterised by a limited supply of upwelling magma, such as the Southwest Indian Ridge. These detachment faults are associated with the development of oceanic core complex structures.

Continental detachment faults

Continental detachment faults are also called

Yerington district of Nevada. There, evidence for rotation of the fault plane comes from tilted volcanic dikes.[5]
However, other authors disagree that these should be called detachment faults. One group of scientists defines detachment faults as follows:

"The essential elements of extensional detachment faults, as the term is used here, are low angle of initial dip, subregional to regional scale of development, and large translational displacements, certainly up to tens of kilometres in some instances." [4]

Detachments faults of this kind (initially low-angle) can be found in the

isostatic uplift and doming of the more ductile material beneath.[6]

Low angle normal faulting is not explained by Andersonian fault mechanics.[7] However, slip on low angle normal faults could be facilitated by fluid pressure, as well as by weakness of minerals in wall rocks. Detachment faults may also initiate on reactivated thrust fault surfaces.[6]

Oceanic detachment faults

Oceanic detachment faults occur at

spreading ridges where magmatic activity is not enough to account for the entire plate spreading rate. They are characterized by long domes parallel to the spreading direction (oceanic core complexes of the footwall). Slip on these faults can range from tens to hundreds of km. They cannot be structurally restored, as slip on the fault exceeds the thickness of oceanic crust (~30 km compared to ~6 km, for example).[6]

While occurring at relatively amagmatic spreading centres, the footwalls of these detachment faults are much more influenced by magmatism than in continental settings. In fact, they are often created by ‘continuous casting’: new footwall is continually being generated by mantle or melt from a magma chamber as slip occurs on the fault.

hydrothermally altered than in continental settings.[6]

In contrast to many detachment faults in continental settings, oceanic detachment faults are usually rolling hinge normal faults, initiating at higher angles and rotating to low angles.[6]

References

  1. ^ National Park Service. "Glossary of Geologic Terms" [1]
  2. ^ Fossen H. (1992). The role of extensional tectonics in the Caledonides of South Norway. Journal of Structural Geology, 14:1033–1046.
  3. S2CID 129275058
    .
  4. ^ a b c d Davis, G. A., & Lister, G. S., 1988. Detachment faulting in continental extension: Perspectives from the southwestern US Cordillera. Spec. Pap. Geol. Soc. Am, 218, 133-159.[2]
  5. ^ Proffett, J. M. (1977). Cenozoic geology of the Yerington district, Nevada, and implications for the nature and origin of Basin and Range faulting. Geological Society of America Bulletin, 88(2), 247-266. [3]
  6. ^ a b c d e f g John, B. E., & Cheadle, M. J., 2010. Deformation and alteration associated with oceanic and continental detachment fault systems: Are they similar?.Geophysical Monograph Series, 188, 175-205.[4] Archived 2014-04-14 at the Wayback Machine
  7. ^ Kearey, P., Klepeis, K.A., Vine, F.J. (2009) Global Tectonics (3rd edition). Wiley-Blackwell.

Further reading

  • George H Davis, Stephen J Reynolds, (1996), Structural Geology of Rocks and Regions, 2nd Edition, John Wiley and Sons Inc.
    ISBN 0-471-52621-5
    .
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