Magmaticsedimentary

Magmaticsedimentary is a term used in geology to describe rocks or rock sequences that display evidence of both magmatic (igneous) and sedimentary processes in their history. The term is not widely standardized and may appear in discussions of integrated crustal evolution or niche studies of basin magmatism. In practice, magmaticsedimentary assemblages are typically interpreted as sedimentary rocks that incorporate magmatic material or as volcaniclastic deposits that have undergone subsequent diagenesis, cementation, or metamorphic overprint.

Formation and characteristics

Magmaticsedimentary rocks can form when volcanic or igneous material is deposited within a sedimentary environment, producing volcaniclastic sediments such as ash-rich sandstones or lithic-rich mudstones. They can also arise from partial assimilation or intermixing of magma with a sedimentary basin, leading to the inclusion of igneous clasts, glass shards, or phenocrysts within a sedimentary matrix. Textures may include angular igneous fragments, glass fragments, and a fine-grained matrix that records diagenetic or hydrothermal alteration. Geochemically, these rocks may show mixed signatures, with igneous elemental patterns overprinted by sedimentary sorting and weathering.

Occurrence and interpretation

Magmaticsedimentary concepts are often applied in regions with episodic volcanic activity adjacent to sedimentary basins, such as convergent margins or continental rift zones. Their study helps reconstruct the timing of magmatic events relative to sedimentation, the degree of magmatic contribution to sediment supply, and the post-depositional history of diagenesis and alteration.

See also

Volcaniclastic rock, volcanism, sedimentary rock, diagenesis, igneous petrology.