Dike (geology)


Dike (geology)
Banded gneiss with dike of granite orthogneiss.
An intrusion (Notch Peak monzonite) inter-fingers (partly as a dike) with highly-metamorphosed host rock (Cambrian carbonate rocks). From near Notch Peak, House Range, Utah.

A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across

  • planar wall rock structures, such as bedding or foliation
  • massive rock formations, like igneous/magmatic intrusions and salt diapirs.

Dikes can therefore be either intrusive or sedimentary in origin.

Contents

Magmatic dikes

A diabase dike crosscutting horizontal limestone beds in Arizona.
A small dike on the Baranof Cross-Island Trail, Alaska.
Dikes in the Black Canyon of the Gunnison National Park, Colorado, USA
.

An intrusive dike is an igneous body with a very high aspect ratio, which means that its thickness is usually much smaller than the other two dimensions. Thickness can vary from sub-centimetre scale to many metres, and the lateral dimensions can extend over many kilometres. A dike is an intrusion into an opening cross-cutting fissure, shouldering aside other pre-existing layers or bodies of rock; this implies that a dike is always younger than the rocks that contain it. Dikes are usually high angle to near vertical in orientation, but subsequent tectonic deformation may rotate the sequence of strata through which the dike propagates so that the latter becomes horizontal. Near horizontal, or conformable intrusions, along bedding planes between strata are called intrusive sills.

Sometimes dikes appear as swarms, consisting of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event. The world's largest dike swarm is the Mackenzie dike swarm in the Northwest Territories, Canada.[1]

Shiprock, New Mexico, the volcanic neck in the distance, with radiating dike on its south side. Photo credit: USGS Digital Data Series

Dikes often form as either radial or concentric swarms around plutonic intrusives, volcanic necks or feeder vents in volcanic cones. The latter are known as ring dikes.

Dikes can vary in texture and their composition can range from diabase or basaltic to granitic or rhyolitic, but on a global perspective the basaltic composition prevails, manifesting ascent of vast volumes of mantle-derived magmas through fractured lithosphere throughout Earth history. Pegmatite dikes are extremely coarse crystalline granitic rocks often associated with late-stage granite intrusions or metamorphic segregations. Aplite dikes are fine grained or sugary textured intrusives of granitic composition.

Sedimentary dikes

Clastic dike (left of notebook) in the Chinle Formation in the Island In the Sky District of Canyonlands National Park, Utah.

Sedimentary dikes or clastic dikes are vertical bodies of sedimentary rock that cut off other rock layers. They can form in two ways:

  • When a shallow unconsolidated sediment is composed of alternating coarse grained and impermeable clay layers the fluid pressure inside the coarser layers may reach a critical value due to lithostatic overburden. Driven by the fluid pressure the sediment breaks through overlying layers and forms a dike.
  • When a soil is under permafrost conditions the pore water is totally frozen. When cracks are formed in such rocks, they may fill up with sediments that fall in from above. The result is a vertical body of sediment that cuts through horizontal layers: a dike.
Magmatic dikes radiating from West Spanish Peak, Colorado, USA

See also

References

  1. ^ Supressing Varying Directional Trends Retrieved on 2007-07-28

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • dike — dike1 diker, n. /duyk/, n., v., diked, diking. n. 1. an embankment for controlling or holding back the waters of the sea or a river: They built a temporary dike of sandbags to keep the river from flooding the town. 2. a ditch. 3. a bank of earth… …   Universalium

  • Geology of the Grand Teton area — The geology of the Grand Teton area consists of some of the oldest rocks and one of the youngest mountain ranges in North America. The Teton Range, mostly located in Grand Teton National Park, started to grow some 9 million years ago. An older… …   Wikipedia

  • dike ridge — noun 1. geology : a hogback in which the formation resistant to erosion is a dike 2. geology : a small wall like ridge on a glacier resulting from differences in the rate of melting 3. geology : any small wall like ridge (as one along a shore)… …   Useful english dictionary

  • Geology of the Falkland Islands — The geology of the Falkland Islands has its origins in events of more than 400 million years bp, before the Falkland Islands existed as separate entities, with the appearance of intruded dikes in the crust of the supercontinent Gondwana. The… …   Wikipedia

  • Clastic dike — Vertical clastic dike, filled with coarse basaltic sand, cuts lighter colored horizontal beds composed of finer grained material. Quarter for scale. A clastic dike is a seam of sedimentary material that fills a crack in and cuts across… …   Wikipedia

  • Klastischer Dike — Basische Gesteinsgänge in Alaska Dykes (englisch) oder Dikes (amerikanisch) sind plattenartige, meist weit reichende Gesteinskörper aus magmatischem Gestein, die größere Spalten ausfüllen und das umgebende Gestein schneiden oder durchkreuzen. Der …   Deutsch Wikipedia

  • Sedimentärer Dike — Basische Gesteinsgänge in Alaska Dykes (englisch) oder Dikes (amerikanisch) sind plattenartige, meist weit reichende Gesteinskörper aus magmatischem Gestein, die größere Spalten ausfüllen und das umgebende Gestein schneiden oder durchkreuzen. Der …   Deutsch Wikipedia

  • Sheeted-Dike-Komplex — Basische Gesteinsgänge in Alaska Dykes (englisch) oder Dikes (amerikanisch) sind plattenartige, meist weit reichende Gesteinskörper aus magmatischem Gestein, die größere Spalten ausfüllen und das umgebende Gestein schneiden oder durchkreuzen. Der …   Deutsch Wikipedia

  • Mistassini dike swarm — Map of the Matachewan and Mistassini dike swarms of Eastern Canada The Mistassini dike swarm is a 2.5 billion year old Paleoproterozoic dike swarm of western Quebec, Canada. It consists of mafic dikes that were intruded in the Superior …   Wikipedia

  • List of geology topics — This is a list of all articles related to geology that cannot be readily placed on the following subtopic pages: Geology subtopics* Geologic time scale * List of compounds * List of earthquakes * List of elements by name * List of geology of… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.