Dike (geology)

Information about Dike (geology)

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Banded gneiss with dike of granite orthogneiss


A dike or dyke in geology refers to any body that cuts off originally horizontal rocks layers. Dikes can be either intrusive or sedimentary in origin.

Magmatic dikes

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A small dike on the Baranof Cross-Island Trail, Alaska
An intrusive dike is an igneous body. The thickness is usually much smaller than the other two dimensions. Thickness can vary from sub-centimeter scale to many meters in thickness and the lateral dimensions can extend over many kilometers. A dike is an intrusion into a cross-cutting fissure, meaning a dike cuts across other pre-existing layers or bodies of rock, this means 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 lies so that the latter becomes horizontal. Near horizontal or conformable intrusions along bedding planes between strata are called intrusive sills. The world's largest dike swarm is the Mackenzie dyke swarm in the Northwest Territories, Canada.[1]

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Shiprock, New Mexico a 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 or around volcanic necks or feeder vents in volcanic cones. These are known as ring dikes.

Dikes can vary in texture and composition from diabase or basaltic to granitic or rhyolitic. Pegmatite dikes are extremely coarsely 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

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 clayish 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.

See also

References

1. ^ Supressing Varying Directional Trends Retrieved on 2007-07-28
Oceanic crust      0-20 Ma
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intrusion is a body of igneous rock that has crystallized from a molten magma below the surface of the Earth. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto, the Roman god of the underworld.
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Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. Sedimentation is the deposition by settling of a suspended material.
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Igneous rocks (etymology from latin ignis, fire) are rocks formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.
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A fissure vent, also known as a volcanic fissure or simply fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long.
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Tectonics, (from the Greek for "builder", tekton), is a field of study within geology concerned generally with the structures within the crust of the Earth (or other planets) and particularly with the forces and movements that have operated in a region to create these
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stratum (plural: strata) is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural forces.
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In geology, a sill is a tabular pluton that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet.
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The Mackenzie dyke swarm is a 1.2 billion year old dyke swarm, located in the Slave craton of the Northwest Territories, Canada. It is largest dyke swarm known on Earth,[1]
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Northwest Territories
Territoires du Nord-Ouest

Flag Coat of arms
Motto: none

Capital Yellowknife
Largest city Yellowknife
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volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when lava hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can
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Volcanic cones are among the simplest volcano formations in the world. They are built by fragments (called ejecta) thrown up (ejected) from a volcanic vent, piling up around the vent in the shape of a cone with a central crater.
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A ring dike or ring dyke in geology refers to an intrusive igneous body. Their chemistry, petrology and field appearance precisely match those of dikes or sill, but their concentric or radial geometric distribution around a centre of volcanic activity indicates their
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Diabase (IPA: /ˈdʌɪəbeɪs/) is a mafic, holocrystalline, igneous rock equivalent to volcanic basalt or plutonic gabbro. Diabase is also called dolerite in many older British references.
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Basalt (IPA: /ˈbæsɒlt, bəˈsɒlt/) is a common gray to black extrusive volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface.
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Granite (IPA: /ˈɡrænɪt/) is a common and widely occurring type of intrusive, felsic, igneous rock. Granites are usually medium to coarsely crystalline, occasionally with some individual crystals larger than the
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Rhyolite is an igneous, volcanic (extrusive) rock, of felsic (acidic) composition (typically >69% SiO2 — see the TAS classification. It may have any texture from aphanitic to porphyritic.
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Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.

Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite".
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Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat (greater than 150 degrees Celsius) and extreme pressure causing profound
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Aplite (IPA: /ˈaplʌɪt/) in petrology, the name given to intrusive rock in which quartz and feldspar are the dominant minerals.
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A clastic dike is the geological term used to describe a seam of 'foreign' sedimentary material (often breccia) that fills cracks in sedimentary strata. Since sedimentary strata are usually formed by deposition in the horizontal plane, they usually remain in that orientation,
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Permeability, permeable and semipermeable have several meanings:
  • Permeability (electromagnetism), is the degree of magnetization of a material in response to a magnetic field

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Clay is a naturally occurring material, composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried or fired.
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Fluid pressure is the pressure at some point within a fluid, such as water or air.

Fluid pressure occurs in one of two situations:
  1. an open condition, such as the ocean, a swimming pool, or the atmosphere; or
  2. a closed condition, such as a water line or a gas line.

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Overburden pressure, lithostatic pressure, and vertical stress are terms that denote the pressure or stress imposed on a layer of soil or rock by the weight of overlying material.
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permafrost or permafrost soil is soil at or below the freezing point of water (0°C or 32°F) for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic
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Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water.
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Crack may refer to:
  • Crack, a fracture or discontinuation in a body
  • Crack (economics), the value difference between crude oil and oil products or between different oil products, usually expressed as a per-barrel value

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batholith (from Greek bathos, depth + lithos, rock) is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust.
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