Melting of MORB at core–mantle boundary

Gopal K. Pradhan (1) , Guillaume Fiquet (1) , Julien Siebert (2) , Anne-Line Auzende (3, 1) , Guillaume Morard (1) , Daniele Antonangeli (1) , Gaston Garbarino (4)

1 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
2 IPGP - Institut de Physique du Globe de Paris
3 Université de Grenoble
4 ESRF - European Synchrotron Radiation Facility

We investigated the melting properties of natural mid-ocean ridge basalt (MORB) up to core–mantle boundary (CMB) pressures using laser-heated diamond anvil cell. Textural and chemical characterizations of quenched samples were performed by analytical transmission electron microscopy. We used in situ X-ray diffraction primarily for phase identification whereas our melting criterion based on laser power versus temperature plateau combined with textural analysis of recovered solidus and subsolidus samples is accurate and unambiguous. At CMB pressure (135 GPa), the MORB solidus temperature is 3970 (±150) K. Quenched melt textures observed in recovered samples indicate that CaSiO3 perovskite (CaPv) is the liquidus phase in the entire pressure range up to CMB. The partial melt composition derived from the central melt pool is enriched in FeO, which suggests that such melt pockets may be gravitationally stable at the core mantle boundary.

Mots clés: core–mantle boundary; ULVZ; partial melting; experimental mineralogy; high-pressure melting; laser heating

Domaines: Planète et Univers [physics]

Gopal K. Pradhan, Guillaume Fiquet, Julien Siebert, Anne-Line Auzende, Guillaume Morard, et al.. Melting of MORB at core–mantle boundary. Earth and Planetary Science Letters, 2015, 431, pp.247-255. ⟨10.1016/j.epsl.2015.09.034⟩. ⟨hal-01216598⟩