Why dunite has no volcanic equivalent?

Answer 1

Dunite is composed predominantly of olivine. A volcanic rock of dunite composition would need to form from a lava/magma of dunnite composition. A magma of dunite i.e. olivine composition would never be produced from melting of mantle or crustal rocks because olivine melts/crystallises at higher temperatures than most other minerals. Therefore, melting any rock other than dunite itself would produce a magma with a composition less Fe-Mg-rich than dunnite. Dunite forms in 2 ways: When olivine is concentrated by accumulation at the base of a magma chamber (cumulate layaered gabbro); and by chemical reaction between an exsolved basaltic melt and residual peridotite in the lithospheric mantle. Pyroxene in the mantle dissolves and olivine is left behind as a residual material.

Answer 2

Dunite is a type of peridotite rock that is formed deep within the Earth's mantle through processes like partial melting. Its composition and formation conditions do not correspond with those found in volcanic settings, which is why dunite does not have a volcanic equivalent. Instead, dunite is typically brought to the surface through tectonic processes like uplift and erosion.

Answer 3

Dunite has no volcanic equevalent simply because the magma that have dunite composition does not reach or go out in the surface.