melanorites

Melanorites are a type of plutonic igneous rock. They are characterized by their composition, being rich in melilite and feldspathoids, and typically containing clinopyroxene. These rocks are considered rare and are usually found in alkaline intrusive complexes. Their formation is associated with magmas that are undersaturated in silica.

The mineral melilite, a solid solution series between åkermanite and gehlenite, is a defining feature of melanorites. The presence of feldspathoids, such as nepheline or sodalite, indicates that the magma from which the melanorite crystallized was silica-poor. Clinopyroxene, often diopside or augite, is a common mafic mineral found in these rocks.

Melanorites are typically fine-grained to medium-grained in texture. Their color can vary depending on the mineral assemblage, but they often appear dark due to the presence of mafic minerals. They are distinct from melteigites, which are extrusive equivalents, and also from other feldspathoid-bearing rocks like foidites or alkali pyroxenites.

The geological settings where melanorites are found are usually rift zones or continental margins where alkaline magmatism is prevalent. These environments provide the conditions for the generation of silica-undersaturated magmas. Studying melanorites can offer insights into the complex processes of magma genesis and differentiation in alkaline provinces.