basaltdikes

Basaltdikes are subvertical to steeply dipping sheet-like intrusions of basaltic magma that cut across preexisting rocks. They form when low-viscosity basaltic magma intrudes cracks and joints in surrounding rock, often in zones of crustal extension or near volcanic centers. As the magma rises and forces its way through fractures, it cools and crystallizes to form a fine-grained basalt with chilled margins along the contact with wall rocks. Basaltdikes typically occur as part of dyke swarms and can extend for kilometers, though individual dikes may be only a few meters to tens of meters wide. They commonly truncate layering in sedimentary or volcanic rocks, providing time markers for relative dating and records of stress directions at the time of intrusion.

Texture and composition are consistently mafic, with plagioclase, pyroxene, and olivine as primary minerals; many basaltdikes show contact metamorphism or alteration in the surrounding rock near the margins. The presence of basaltic dikes can influence local hydrogeology by acting as conductive pathways for groundwater or hydrothermal fluids. Economic relevance is typically secondary; however, dike swarms can localize mineralization or serve as exploration guides in mafic provinces.

Basaltdikes are globally distributed, commonly associated with flood basalts, volcanic arcs, and extensional tectonic regimes. They are distinguished from sills by their cross-cutting relationship to host rocks and from lava flows by their intrusive nature and crystallized texture rather than surface emplacement.

See also: Dike (geology), Dyke swarm, Basalt, Igneous intrusion.