dike swarm

In geology, a dike is a tabular or sheetlike igneous rock body that is often oriented vertically or steeply inclined to the bedding of surrounding rocks. When multiple parallel dikes are present, they form a dike set, and a large number of these parallel dikes is termed a dike swarm. Dikes can vary greatly in rock composition and often exhibit a porphyritic texture, indicating two crystallization periods. While dikes can range from a few centimeters to over 10 meters in width, they typically average between 0.3 and 6 meters wide. Their length can extend for hundreds of miles, with the Great Dike of Zimbabwe being over 550 km long. During the Proterozoic Eon, continents were stable enough for numerous basic dikes to intrude into extensional fractures, forming large swarms.12