Pyrolite

This model is based on that a pyrolite source can produce mid-ocean ridge basalts (MORB) by partial melting.

[6] The major elements composition of pyrolite is about 44.71 molar percent (mol%) SiO2, 3.98 % Al2O3, 8.18 % FeO, 3.17 % CaO, 38.73 % MgO, 0.13 % Na2O.

[9] 1) A pyrolitic Upper Mantle is mainly composed of olivine (~60 volume percent (vol%)), clinopyroxene, orthopyroxene, and garnet.

The P-wave and S-wave velocities (Vp and Vs) of pyrolite along the 1600 K adiabatic geotherm are shown in Fig.

In the geochemical aspect, it does not satisfy trace elements or isotopic data of Mid-Ocean Ridge Basalts because the pyrolite hypothesis is based on major elements and some arbitrary assumptions (e.g. amounts of basalt and melting in the source).

[17] (2) Eclogite, it is transformed from the Mid-Ocean Ridge Basalt at a depth of ~60 km,[citation needed] exists in the Earth's mantle mainly within the subducted slabs.

Fig.1 The mineral volume fraction in a pyrolitic mantle up to 1000 km depth. [ 7 ] [ 8 ] Ol: olivine; Opx: orthopyroxene; Cpx: clinopyroxene; Gt: garnet; Wad: wadsleyite; Ring: ringwoodite; Pv: perovskite; Fp: ferropericlase; Ca-Pv: calcium perovskite.
Fig. 2 Vp and Vs profiles of pyrolite along the 1600 K adiabatic geotherm [ 2 ]
Fig. 3 Density profile of pyrolite along the 1600 K adiabatic geotherm [ 2 ]
Fig. 4. Mineral proportion of a MORB-transformed eclogite at 250-500 km depth [ 14 ]