气候变化领域集成服务门户(CCPortal): Synthesis, Elasticity, and Spin State of an Intermediate MgSiO3-FeAlO3 Bridgmanite: Implications for Iron in Earth's Lower Mantle

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DOI	10.1029/2020JB019964
	Synthesis, Elasticity, and Spin State of an Intermediate MgSiO3-FeAlO3 Bridgmanite: Implications for Iron in Earth's Lower Mantle
	Zhu F.; Liu J.; Lai X.; Xiao Y.; Prakapenka V.; Bi W.; Alp E.E.; Dera P.; Chen B.; Li J.
发表日期	2020
ISSN	21699313
卷号	125 期号:7
英文摘要	Fe-Al-bearing bridgmanite may be the dominant host for ferric iron in Earth's lower mantle. Here we report the synthesis of (Mg0.5Fe3+0.5)(Al0.5Si0.5)O3 bridgmanite (FA50) with the highest Fe3+-Al3+ coupled substitution known to date. X-ray diffraction measurements showed that at ambient conditions, the FA50 adopted the LiNbO3 structure. Upon compression at room temperature to 18 GPa, it transformed back into the bridgmanite structure, which remained stable up to 102 GPa and 2,600 K. Fitting Birch-Murnaghan equation of state of FA50 bridgmanite yields V0 = 172.1(4) Å3, K0 = 229(4) GPa with K0′ = 4(fixed). The calculated bulk sound velocity of the FA50 bridgmanite is ~7.7% lower than MgSiO3 bridgmanite, mainly because the presence of ferric iron increases the unit-cell mass by 15.5%. This difference likely represents the upper limit of sound velocity anomaly introduced by Fe3+-Al3+ substitution. X-ray emission and synchrotron Mössbauer spectroscopy measurements showed that after laser annealing, ~6% of Fe3+ cations exchanged with Al3+ and underwent the high- to low-spin transition at 59 GPa. The low-spin proportion of Fe3+ increased gradually with pressure and reached 17–31% at 80 GPa. Since the cation exchange and spin transition in this Fe3+-Al3+-enriched bridgmanite do not cause resolvable unit-cell volume reduction, and the increase of low-spin Fe3+ fraction with pressure occurs gradually, the spin transition would not produce a distinct seismic signature in the lower mantle. However, it may influence iron partitioning and isotopic fractionation, thus introducing chemical heterogeneity in the lower mantle. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	bridgmanite; cation exchange; equation of state; ferric iron; lower mantle; spin transition
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187792
作者单位	Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, United States; Hawai'i Institute of Geophysics and Planetology, University of Hawai'i at Mānoa, Honolulu, HI, United States; Earth and Environmental Sciences, Michigan State University, East Lansing, MI, United States; Gemmological Institute, China University of Geosciences, Wuhan, China; HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, United States; Center for Advanced Radiation Sources, University of Chicago, Argonne, IL, United States; Advanced Photon Source, Argonne National Laboratory, Argonne, IL, United States; Department of Geology, University of Illinois at Urbana-Champaign, Urbana, IL, United States; Department of Physics, University of Alabama at Birmingham, Birmingham, AL, United States
推荐引用方式 GB/T 7714	Zhu F.,Liu J.,Lai X.,et al. Synthesis, Elasticity, and Spin State of an Intermediate MgSiO3-FeAlO3 Bridgmanite: Implications for Iron in Earth's Lower Mantle[J],2020,125(7).
APA	Zhu F..,Liu J..,Lai X..,Xiao Y..,Prakapenka V..,...&Li J..(2020).Synthesis, Elasticity, and Spin State of an Intermediate MgSiO3-FeAlO3 Bridgmanite: Implications for Iron in Earth's Lower Mantle.Journal of Geophysical Research: Solid Earth,125(7).
MLA	Zhu F.,et al."Synthesis, Elasticity, and Spin State of an Intermediate MgSiO3-FeAlO3 Bridgmanite: Implications for Iron in Earth's Lower Mantle".Journal of Geophysical Research: Solid Earth 125.7(2020).