horse (geology)

{{short description|Block of rock completely surrounded by mineral veins or fault planes}}

File:Duplex1.png

Image:geologic horse.jpg located near Upheaval Dome, Utah. The fault plane traces from the upper right to the lower left of the image. The horse is the broad lens-shaped feature in the rock defined by the splitting and rejoining of the trace of the fault plane.]]

A horse, in geology, is any block of rock completely separated from the surrounding rock either by mineral veins or fault planes. In mining, a horse is a block of country rock entirely encased within a mineral lode.{{Cite web |url=http://www.minersoc.org/pages/Archive-MM/Volume_16/16-74-124.pdf |title=Butler, F.H. 1911. The brecciation of mineral veins. |access-date=2009-08-16 |archive-date=2017-08-13 |archive-url=https://web.archive.org/web/20170813111223/http://www.minersoc.org/pages/Archive-MM/Volume_16/16-74-124.pdf |url-status=dead }} In structural geology the term was first used to describe the thrust-bounded imbricates found within a thrust duplex.Dennis, J.G. 1967. International tectonic dictionary. AAPG Memoir 7, 196pp. In later literature it has become a general term for any block entirely bounded by faults, whether the overall deformation type is contractional, extensional or strike-slip in nature.[http://geology.geoscienceworld.org/cgi/content/abstract/18/5/419 Root, K.G. 1990. Extensional duplex in the Purcell Mountains of southeastern British Columbia. Geology, 18, 419-421]{{citation|title=Three-dimensional shuffling of horses in a strike-slip duplex: an example from the Lambertville sill, New Jersey|journal=Tectonophysics|volume=258|issue=1–4|pages=53–70|doi=10.1016/0040-1951(95)00173-5|year=1996|last1=Laney|first1=Stephen E|last2=Gates|first2=Alexander E|bibcode=1996Tectp.258...53L }}