The Stability Of (Mg,Fe)SiO₃-Perovskite And The Chemical Reaction Between Iron And (Mg,Fe)SiO₃-Perovskite At Lower Mantle Conditions

In this thesis, the shock recovery experiments were conducted to check the phase stability of the dominant phase of the lower mantle- (Mg, Fe)SiO₃-perovskite, and the possible chemical reaction between iron and (Mg, Fe)SiO)3-perovskite. These researches supply the fundamentals phycical constrains on establishing the mineralogical model of the Earth's lower mantle and the chemical composition of core-mantle boundary (CMB).The main work and achievements of this thesis are as following:(1) Two shots of shock recovery experiments with the initial sample of MgO+SiO₂ were conducted at pressure ranges of 69¹00GPa (the corresponding temperature is estimated as 2600-4300K). This is one of innovative experimental designs of this thesis. The recovered samples were analysesed by X-ray diffraction (XRD). The XRD results indicate that the main composition of recovered samples is SiO₂ and Mg₂SiO₄, no evidence of the oxides MgO was observed. Two shots of shock recovery experiments with the initial sample of (Mg_0.92, Fe_0.08)SiO₃ enstatite were also conducted. The XRD results were just the same as previous researches, which indicated that the main phase of the recovered samples is not perovskite structure, but single-chain structure enstatite. Especially, no evidence of the oxides SiO₂ and (Mg_0.92, Fe_0.08 )O in recovered samples was observed. We inferred that there is no possibility for the chemical decomposition from (Mg_0.92, Fe_0.08)SiO₃ to oxides SiO₂ and (Mg_0.92, Fe_0.08)O under shock compression up to 115 GPa.(2) Shock recovery experiments with the initial sample of (Mg_0.92, Fe_0.08)SiO₃+Fe were conducted at pressure range from 78GPa to 115GPa (the corresponding temperature is estimated as 3000-5000K) to check the possible chemical reactions between iron and (Mg_0.92, Fe_0.08)SiO₃ perovskite. This is the first time to do such experiments in this field. The XRD observations showed the main composition of the two recovered samples is Fe and (Mg, Fe)₂SiO₄. Comparing with the above recovery experiments of MgO+SiO₂, we inferred that chemical reaction between iron and perovskite happened, SiO₂ and (Mg, Fe)O were formed during shock compression. It suggest that reactions between liquid iron...