During ultramafic alteration can serpentinite form?

Can basalt be the parent rock of serpentinite?


1 Answer 1


Serpentine can form in basalt, but it is likely to be less extensive than in some other mafic rocks such as dunite or harzburgite.

Serpentinization is primarily associated with the minerals olivine and pyroxene, whose oxide components are poor in silica and rich in iron and magnesium oxides. The serpentization reaction involves water displacing some of the iron and magnesium oxides, the latter being stabilized by further reactions with water (magnesium oxide -> magnesium hydroxide/brucite, iron oxide -> magnetite) or with other materials present such as carbon dioxide (forming a variety of products). The silicate is converted to a hydrated mineral or minerals containing less iron and magnesium than the original olivine or pyroxene.

Basalt contains some olivine and pyroxene and thus can undergo serpentinization. But it also contains large amounts of other minerals such as plagioclase feldspar and biotite mica, which either do not contain significant amounts of iron and magnesium (plagioclase) or have less of these and in a less reactive lattice structure (biotite and some other components) than olivine and pyroxene. So serpentinization is limited in basalt compared with more purely mafic or ultramafic rocks that contain more of the reactive minerals olivine and pyroxene.


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