alkalinebasalt

Alkaline basalt is a volcanic rock that is relatively rich in alkali metals, such as sodium and potassium, compared to tholeiitic basalt. This higher alkali content leads to distinct mineralogical and chemical characteristics. It typically contains minerals like nepheline, alkali feldspar, and sometimes olivine, though its composition can vary. The texture of alkaline basalt can range from fine-grained to porphyritic, with larger crystals of phenocrysts embedded in a finer groundmass.

Geochemically, alkaline basalts are characterized by elevated concentrations of incompatible trace elements. Their formation is often associated with conditions of lower partial melting or specific mantle source compositions. Alkaline basalts are found in a variety of tectonic settings, including continental rifts, intraplate volcanic provinces, and sometimes at divergent plate boundaries. Examples include volcanic fields in East Africa, Hawaii, and parts of the Canadian shield. The study of alkaline basalts provides insights into the evolution of the Earth's mantle and processes occurring beneath the surface.