mantledepleted

Mantle-depleted is a geological term used to describe regions of the Earth's mantle that have been depleted in highly incompatible elements relative to primitive mantle due to the extraction of melt. This depletion is a consequence of partial melting, where melt rises to form crust and leaves behind a residual mantle with lower concentrations of certain trace elements.

The depletion process occurs when peridotite undergoes melting and produces basaltic magma, which is removed from the mantle and forms the crust. The residue becomes chemically depleted in elements that preferentially enter melt, such as potassium, uranium, thorium, and many rare earth elements. A well-known application of this concept is the depleted MORB mantle, or DMM, which is used as a reference source for mid-ocean ridge basalts.

Geochemical and isotopic evidence supports the existence of mantle-depleted domains. MORB compositions repeatedly show lower levels of incompatible elements compared with primitive mantle or enriched reservoirs, and isotopic systems such as Sr-Nd-Pb help distinguish depleted mantle components from enriched or primitive sources. The mantle is not uniformly depleted; regional heterogeneities arise from varying melting histories, plate tectonics, and later subduction, which can add enriched materials back into mantle domains.

Mantle depletion has important implications for understanding planetary differentiation, mantle convection, and crust formation. It explains why certain basalts sampled at mid-ocean ridges carry distinct, depleted trace element signatures, and it provides a framework for interpreting the chemical diversity of volcanic rocks both at plate boundaries and within mantle plumes.