ĭikes often form as either radial or concentric swarms around plutonic intrusives, volcanic necks or feeder vents in volcanic cones. The world’s largest dike swarm is the Mackenzie dike swarm in the Northwest Territories, Canada. Sometimes dikes appear in swarms, consisting of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event. Near-horizontal, or conformable intrusions, along bedding planes between strata are called intrusive sills.

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 dike becomes horizontal. 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. Thickness can vary from sub-centimeter scale to many meters, and the lateral dimensions can extend over many kilometres. Magmatic DikesĪn 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. Clastic dikes are formed when sediment fills a pre-existing crack.

Magmatic dikes form when magma intrudes into a crack then crystallizes as a sheet intrusion, either cutting across layers of rock or through an unlayered mass of rock. Dikes can be either magmatic or sedimentary in origin. A magmatic dike cross-cutting horizontal layers of sedimentary rock, in Makhtesh Ramon, IsraelĪ dike is a sheet of rock that formed in a fracture in a pre-existing rock body.

Magma crack