kimberlites; metasomatised mantle; iron carbides; deep carbon cycle ; carbonatites; physical melt properties; carbon transfer; banded iron formation
Ghosh S, Schmidt MW (2014), Melting of phase D in the lower mantle and implications for recycling and storage of H2O in the deep mantle., in Geochim. Cosmochim. Acta
, online, GCA8881-1.
Ghosh S, Litasov K, Ohtani E (2014), Phase relations and melting of carbonated peridotite between 10 and 20 GPa: a proxy for alkali- and CO2-rich silicate melts in the deep mantle., in Contrib. Min. Pet.
, 167 (2), 1-23.
Rohrbach A, Ghosh G, Schmidt MW, Wijbrans CH, Klemme S (2014), The stability of Fe-Ni carbides in the Earth's mantle: evidence for a low Fe-Ni-C melt fraction in the deep mantle., in Earth Planet Sci Lett
, 388, 211-221.
Ghosh Sujoy (2013), Effect of water in depleted mantle on post-spinel transition and implication for 660 km seismic discontinuity at the Earth's mantle., in Earth and Planetary Science Letters
, 371-372, 103-111.
Rosa AD, Mezouar M, Gabarino G, Bouvier P, Ghosh S, Rohrbach A, Sanchez-Valle C (2013), Single-crystal equation of state of phase D to lower mantle pressures and the effect of hydration on the buoyancy of deep subducted slabs., in J. Geophy. Res. - Solid Earth
, 118, 6124-6133.
Ballhaus C, Laurenz V, Muenker C, Raul OC, Fonseca ROC, Albarede F, Rohrbach A, Lagos M, Schmidt MW, Jochum K, Stoll B, Weis U, Helmy H (2013), The U/Pb ratio of the Earth's mantle - a signature of late volatile addition., in Earth Planet. Sci. Lett.
, 362, 237-245.
Rosa AD, Sanchez-Valle C, Ghosh S (2012), Elasticity of phase D and implication for the degree of hydration of deep suducted slabs., in Geophys.Res.Lett.
, 39, L06304.
Grassi D, Schmidt MW, Günther D (2012), Element partitioning during pelite melting at 8, 13, and 22 GPa and the sediment signature in the EM mantle component., in Earth Planet. Sci. Lett.
, 327-328, 177-190.
Ghosh Sujoy, Single-crystal equation of state of dense hydrous magnesium silicate phase D to lower mantle pressures., in Journal of Geophysical Research
The deep carbon cycle essentially consists of three steps: burial of carbon contained in the subducting lithosphere, transfer of carbon from the lithosphere into the mantle, and mantle derived magmatism bringing carbon back to the surface. This project is mainly concerned with the carbon transfer step, an almost unstudied process, that we will investigate through high pressure experiments from 2-35 GPa, at temperatures of 1000-2500 oC and controlled oxygen fugacities. At deeper mantle depths, carbon is most likely transferred in the form of carbonate melts and we will experimentally investigate how these form in banded iron formations, an ancient sediment type which fate in the mantle remains unknown. Defining the melting conditions and melt compositions of this lithology will allow to understand what geochemical signal might be derived from them, and whether these lithologies could subduct deeply without major chemical modification. Secondly, we will determine the mineralogy and geochemistry of mantle reservoirs resulting from the infiltration of alkali-rich carbonatites derived from pelitic sediments (these were investigated in a previous PhD). Such reservoirs are most likely at the origin of many kimberlites and ultrapotassic melts and the quantification of their geochemistry and mineralogy will allow to model the formation of such ultrapotassic melts. Third, when oxidized carbonate melts migrate into the deep reduced mantle (likely to be metal saturated), iron-nickel carbides or Fe-Ni-C melts should result during redox freezing of these carbonate melts. We will determine subsolidus and minimum melting relations in the Fe-Ni-C system with the aim to define the hitherto unknown role of iron carbides in the mantle. Finally, we will investigate two fundamental physical properties of deep carbonate liquids, both necessary for physical melt migration models. We will determine high pressure densities of carbonate melts by floating/sinking experiments and the wetting properties by measuring the contact angles between carbonatite and mantle minerals. The total of the results should constitute a crucial step forwards in our understanding of the deep carbon transfer (and cycle).