KeywordsMantle Plume Magmatic Intrusion Dike Swarm Fracture Floor Spatter Cone
A magmatic vertical sheet intrusion that has penetrated into a preexisting body of rock.
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).
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).
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).
Some fractures on impact crater floors are supposedly formed through dike injections in the crater subsurface (Fractured Floor Craters).
Shallow graben resulted from the extensive pressure and tensile stress on the rock into which the dike intruded (Graben System, Mars).
Pit chain/maar is caused by phreatomagmatic explosions resulted from dike intrusion into a near-surface volatile-rich layer.
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).
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)).
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).
Cliff (Mège 1999).
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).
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).
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