气候变化领域集成服务门户(CCPortal): The Role of Redox on Bridgmanite Crystal Chemistry and Calcium Speciation in the Lower Mantle

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DOI	10.1029/2020JB020783
	The Role of Redox on Bridgmanite Crystal Chemistry and Calcium Speciation in the Lower Mantle
	Creasy N.; Girard J.; Eckert J.O.; Jr.; Lee K.K.M.
发表日期	2020
ISSN	21699313
卷号	125 期号:10
英文摘要	The amount of ferric iron Fe3+ in the lower mantle is largely unknown and may be influenced by the disproportionation reaction of ferrous iron Fe2+ into metallic Fe and Fe3+ triggered by the formation of bridgmanite. Recent work has shown that Fe3+ has a strong effect on the density and seismic wave speeds of bridgmanite and the incorporation of impurities such as aluminum. In order to further investigate the effects of ferric iron on mineral behavior at lower mantle conditions, we conducted laser-heated diamond-anvil cell (LHDAC) experiments on two sets of samples nearly identical in composition (an aluminum-rich pyroxenite glass) except for the Fe3+ content; with one sample with more Fe3+ (“oxidized”: Fe3+/ΣFe ~ 55%) and the other with less Fe3+ (“reduced”: Fe3+/ΣFe ~ 11%). We heated the samples to lower mantle conditions, and the resulting assemblages were drastically different between the two sets of samples. For the reduced composition, we observed a multiphase assemblage dominated by bridgmanite and calcium perovskite. In contrast, the oxidized material yielded a single phase of Ca-bearing bridgmanite. These Al-rich pyroxenite samples show a difference in density and seismic velocities for these two redox states, where the reduced assemblage is denser than the oxidized assemblage by ~1.5% at the bottom of the lower mantle and slower (bulk sound speed) by ~2%. Thus, heterogeneities of Fe3+ content may lead to density and seismic wave speed heterogeneities in Earth's lower mantle. ©2020. American Geophysical Union. All Rights Reserved.
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/187529
作者单位	Department of Earth and Planetary Sciences, Yale University, New Haven, CT, United States; Department of Geophysics, Colorado School of Mines, Golden, CO, United States; Lawrence Livermore National Laboratory, Livermore, CA, United States
推荐引用方式 GB/T 7714	Creasy N.,Girard J.,Eckert J.O.,et al. The Role of Redox on Bridgmanite Crystal Chemistry and Calcium Speciation in the Lower Mantle[J],2020,125(10).
APA	Creasy N.,Girard J.,Eckert J.O.,Jr.,&Lee K.K.M..(2020).The Role of Redox on Bridgmanite Crystal Chemistry and Calcium Speciation in the Lower Mantle.Journal of Geophysical Research: Solid Earth,125(10).
MLA	Creasy N.,et al."The Role of Redox on Bridgmanite Crystal Chemistry and Calcium Speciation in the Lower Mantle".Journal of Geophysical Research: Solid Earth 125.10(2020).