The composition of gases extracted by primary planetary magmas is accounted for the large-scale melting of the early mantle in the presence of the metallic Fe phase. The molten metallic Fe phase and the melted silicate material have experienced gravitational migration that exerted influence upon the formation of the metallic core of the planet. The melting should have been accompanied by the formation of volatile compounds, which composition was controlled by the interaction of H, C and N with silicate and metallic melts, a process that remains largely unknown as yet.
In a series of experiments in the system Fe-bearing melt + molten Fe rich metallic phase (0.1-12 % Si) + C (graphite) + H2 carried out at 4 GPa and 1520-1600oC and logfO2 (oxygen fugacity) =1 -5 below IW oxygen buffer, we have characterised the nature (oxidised versus reduced) and quantified the abundance of C, H and N-compound dissolved in an iron bearing silicate melt. The experimental results on the interaction of H, C, N with silicate melts revealed an important feature of redox reactions in silicate melts. It appears that a large scale melting of growth Earth in area of the Fe-Si alloy stability could be associated with melts containing dissolved both oxidized (OH, H2O) and reduced (CH4, H2) components of hydrogen and carbon species. Dual speciation of nitrogen in melt (N2, NH3,NH4+) under high pressure and fO2 may have significant implication concerning of N-species formation in reduce planetary magmas.
Support: Prog. No. 18 RAS, ESD RAS project 7-1.2, RFBR grant