Effect of Ca2+and Fe2+on the equation of state of MgSiO3orthopyroxene

摘要: Room temperature equations of state (EOSs) have been determined for synthetic and natural orthopyroxenes on near the (Mg,Fe)SiO3 join by single-crystal X-ray diffraction to a maximum pressure 11 GPa. The values room bulk moduli, K0,T, its derivative, K0′, are shown be independent form equation used fit data. Variation in Fe2+ content orthopyroxene has very little effect either K0,T or with EOS parameters FeSiO3 orthoferrosilite being K0,T=95.1 (3.0) GPa, K0′=10.6 (1.6), both within one combined experimental estimated standard deviation those previously MgSiO3 orthoenstatite. However, substitution even small amounts Ca2+ (and Al3+) structure causes an increase some 14%. density difference between orthoenstatites (calculated from at 10 GPa) is order 3.4%, corresponding unit-cell volume ∼0.3%. It concluded that pure orthoenstatite not good representation pyroxene component Earth's upper mantle.