摘要
The temperature dependence of the Al2O3 solubility in bridgmanite has been determined in the system MgSiO3–Al_(2)O_(3)at temperatures of 2750–3000 K under a constant pressure of 27 GPa using a multi-anvil apparatus.Bridgmanite becomes more aluminous with increasing temperatures.A LiNbO3-type phase with a pyrope composition(Mg_(3)Al_(2)Si_(3)O_(12))forms at 2850 K,which is regarded as to be transformed from bridgmanite upon decompression.This phase contains 30 mol%Al_(2)O_(3)at 3000 K.The MgSiO3 solubility in corundum also increases with temperatures,reaching 52 mol%at 3000 K.Molar volumes of the hypothetical Al_(2)O_(3)bridgmanite and MgSiO_(3)corundum are constrained to be 25.950.05 and 26.24±0.06 cm^(3)/mol,respectively,and interaction parameters of non-ideality for these two phases are 5.6±0.5 and 2.2±0.5 KJ/mol,respectively.The increases in Al^(2)O^(3)and MgSiO^(3)contents,respectively,in bridgmanite and corundum are caused by a larger entropy of Al_(2)O_(3)bridgmanite plus MgSiO_(3)corundum than that of MgSiO_(3)bridgmanite plus Al_(2)O_(3)corundum with temperature,in addition to the configuration entropy.Our study may help explain dynamics of the top lower mantle and constrain pressure and temperature conditions of shocked meteorites.
基金
Z.L.was financially supported by the Bayerisches Geoinstitut Visitor’s Program and the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.45119031C037)
This project has received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(Proposal No.787527)
It is also supported by research grants to T.K.(BMBF:05K13WC2,05K16 WC2
DFG:KA3434/3–1,KA3434/7–1,KA3434/8–1,KA3434/9–1)
Z.L.(the National Science Foundation of China Grant No.41902034).
