Dike (Igneous)

Living reference work entry
DOI: https://doi.org/10.1007/978-1-4614-9213-9_112-1

Keywords

Mantle Plume Magmatic Intrusion Dike Swarm Fracture Floor Spatter Cone 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Definition

A magmatic vertical sheet intrusion that has penetrated into a preexisting body of rock.

Synonyms

Magmatic dike. Alternative spelling: dyke; Vertical intrusion

Description

A solidified near-vertical subsurface magma body that penetrates through one or more layers of preexisting rock bodies or layers (regardless of rock type). The thickness of a dike is much smaller (cm to meters) than the other dimensions (kilometers), forming a sheetlike structure. Similar but lateral intrusions that form between rock layers are called sills (Magmatic intrusion structure). Dikes per se do not penetrate to the surface, but several landform types may betray their presence. Areal and differential erosion may expose them directly as exhumed dikes. Dike-indicative features are linear or slightly curvilinear over long distances (Head et al. 2006), often appearing in subparallel groups (Korteniemi et al. 2010). They generally cross terrain irrespective of topography (Head et al. 2006). During dike formation and propagation, the magma may reach the surface, causing eruptions (Fissure Vent).

Morphometry

Ridges interpreted as surface manifestations of subsurface dikes on Mars are meters to hundreds of meters in width, up to thousands of kilometer long (Head et al. 2006).

Subtypes

Special cases include:
  1. (1)

    Giant dike swarms are radiating dike groups extending hundreds to thousands of kilometers. On Earth they are associated with mantle plume head events (Ernst et al. 2001*) (Large ignious province, Radiating Lineament System).

     
  2. (2)

    Radial dikes and ring dikes occur around volcanic centers (Chadwick and Howard 1991; Ernst et al. 2001; Russell and Head 2003).

     
  3. (3)

    Some fractures on impact crater floors are supposedly formed through dike injections in the crater subsurface (Fractured Floor Craters).

     
  4. (4)

    Close subparallel groups: Ridged bands on Europa are proposed to be cryomagmatic dike swarm-like features (Kattenhorn and Hurford 2009).

     

Interpretation

Many features can be interpreted as dikes (see Fig. 3 for schematic illustrations). These include both indirect evidence (surface manifestations of subsurface dike segments) and direct evidence (exposed cross sections or dike bodies on the surface):
  1. (1)

    Linear or en echelon fractures formed above the dike body. Note that many processes may cause similar features (Fracture, Linear Ridge Types).

     
  2. (2)

    Shallow graben resulted from the extensive pressure and tensile stress on the rock into which the dike intruded (Graben System, Mars).

     
  3. (3)

    Pit chain/maar is caused by phreatomagmatic explosions resulted from dike intrusion into a near-surface volatile-rich layer.

     
  4. (4)

    Fissure vent: when a dike penetrates the surface, a fissure eruption occurs, and various volcanic features may be formed (e.g., spatter cones, pyroclastic halos, lava flows, volcanoes).

     
  5. (5)

    Linear or broadly arcuate, narrow ridge (Fig. 1): differentially eroded surface, where a remnant and erosion-resistant is exposed as an individual linear ridge when the surrounding, more easily erodible material has been removed. In the case of a dike swarm, a system of subparallel ridges is observed (e.g., Huygens–Hellas giant dike system; Head et al. 2006) (linear ridge types (various origins)).

     
  6. (6)

    Partly eroded and/or cross-cut surface with a lineation (Fig. 2) or promontory on a wall. Caused by e.g., faulting or fluvial linear erosion).

     
  7. (7)

    Cliff (Mège 1999).

     
  8. (8)
     
Fig. 1

A 37-km-long segment of a ~70-km-long arcuate ridge, a candidate dike (Head et al. 2006). THEMIS I08224016 at 6°S 63°E (NASA/JPL/ASU)

On Earth dikes are usually identified from direct exposures (caused by, e.g., erosion) (Fig. 2) or in the case of active dikes also earthquakes (caused by rock fracturing in front of the propagating dike). On Venus and Mars the presence of dikes is mainly inferred from associated volcanic morphology and surface deformation (Ernst et al. 2001).
Fig. 2

Basalt dike amidst granite. Socotra Island, Indian Ocean (Photo by A. Lukashov 2010)

Formation

A dike is a vertical or near-vertical intrusion of magma into rock strata that propagated outward from the source region. They may propagate along the minimum principal stress trajectory fracturing the rock ahead; they may also follow and fill preexisting local fractures (Mège 1999; Head et al. 2006; Fig. 3).
Fig. 3

Illustration of surface manifestation types of near-surface dikes; see text for details (Modified from Korteniemi et al. 2010). Features are not to scale (Figure by Jarmo Korteniemi 2012)

Prominent Examples

Mars: northeast of Huygens crater (Head et al. 2006), Hellas basin and surroundings (Head et al. 2006; Korteniemi et al. 2010), Tharsis–Alba Patera region, and Tempe Terra (Fig. 4; Manfredi and Greeley 2012), Elysium (Russell and Head 2003; Fig. 5).
Fig. 4

Ridges with an axial trough in the highly fractured Tempe Terra interpreted as volcanic dikes (Moore 2001; Manfredi and Greeley 2012). CTX P15_006863_2129_XN_32N086W at 33°N 273°E (NASA/JPL/MSSS)

Fig. 5

Individual and coalesced graben (fossae), proposed to form due to subsurface dike propagation in a cryosphere, with accompanying sinuous lava channels, Mars at 26°N 137°E, east of Elysium Mons (Russell and Head 2003). THEMIS Day IR mosaic (NASA/JPL/ASU)

Distribution

Dike orientation may be radial or concentric about volcanoes (Mège 1999). Giant dike swarms have been identified on Earth (30), Venus (118), and Mars (18) (Ernst et al. 2001*).

Significance

Dikes indicate endogenic heating and they may be associated with larger volcanic centers. Especially dike swarms cause a measurable addition of material and subsequent extension of the crust. Exhumed dikes indicate significant regional erosion. On Mars, dikes may cause ground ice melting, thus allowing groundwater to escape to the surface (Russell and Head 2003; Fig. 5).

Astrobiological Significance

They may provide heat for subsurface ice melting or water release to the surface on Mars (Scott and Wilson 1998; Neather and Wilson 2009).

Terrestrial Analog

One of the most spectacular exposures of a dike is Ship Rock, New Mexico, USA. Dikes are found all around the Earth in regions with both recently and ancient magmatic intrusions (e.g., Iceland, age only few Ma; highly deformed Fennoscandian shield, age 1–3 Ga).

Origin of Term

Dike, dyke (English): a wall of stone or of turf; from old English dictionary, trench, ditch, or moat (Hall 1916).

See Also

References

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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Earth and Space Physics, Department of PhysicsUniversity of OuluOuluFinland