DOI: 10.1016/j.epsl.2018.03.004
Scopus记录号: 2-s2.0-85044160662
论文题名: Phase transition and thermal equations of state of (Fe,Al)-bridgmanite and post-perovskite: Implication for the chemical heterogeneity at the lowermost mantle
作者: Sun N. ; Wei W. ; Han S. ; Song J. ; Li X. ; Duan Y. ; Prakapenka V.B. ; Mao Z.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 490 起始页码: 161
结束页码: 169
语种: 英语
英文关键词: bridgmanite
; chemical heterogeneity
; lowermost mantle
; phase boundary
; post-perovskite
; thermal equations of state
Scopus关键词: Experimental mineralogy
; Perovskite
; Phase boundaries
; Seismic prospecting
; Seismology
; Structural geology
; Velocity
; X ray diffraction
; bridgmanite
; Chemical heterogeneities
; Core-mantle interaction
; Laser-heated diamond anvil cells
; Lowermost mantle
; Mid ocean ridge basalts
; Post perovskite
; Synchrotron x ray diffraction
; Equations of state
; aluminum
; chemical composition
; equation of state
; iron
; lower mantle
; mantle chemistry
; mid-ocean ridge basalt
; perovskite
; phase transition
; Alaska
; United States
英文摘要: In this study, we have determined the phase boundary between Mg0.735Fe0.21Al0.07Si0.965O3-Bm and PPv and the thermal equations of state of both phases up to 202 GPa and 2600 K using synchrotron X-ray diffraction in laser heated diamond anvil cells. Our experimental results have shown that the combined effect of Fe and Al produces a wide two-phase coexistence region with a thickness of 26 GPa (410 km) at 2200 K, and addition of Fe lowers the onset transition pressure to 98 GPa at 2000 K, consistent with previous experimental results. Furthermore, addition of Fe was noted to reduce the density (ρ) and bulk sound velocity (VΦ) contrasts across the Bm-PPv phase transition, which is in contrast to the effect of Al. Using the obtained phase diagram and thermal equations of state of Bm and PPv, we have also examined the effect of composition variations on the ρ and VΦ profiles of the lowermost mantle. Our modeling results have shown that the pyrolitic lowermost mantle should be highly heterogeneous in composition and temperature laterally to match the observed variations in the depth and seismic signatures of the D″ discontinuity. Normal mantle in a pyrolitic composition with ∼10% Fe and Al in Bm and PPv will lack clear seismic signature of the D″ discontinuity because the broad phase boundary could smooth the velocity contrast between Bm and PPv. On the other hand, Fe-enriched regions close to the cold slabs may show a seismic signature with a change in the velocity slope of the D″ discontinuity, consistent with recent seismic observations beneath the eastern Alaska. Only regions depleted in Fe and Al near the cold slabs would show a sharp change in velocity. Fe in such regions could be removed to the outer core by strong core-mantle interactions or partitions together with Al to the high-pressure phases in the subduction mid ocean ridge basalts. Our results thus have profound implication for the composition of the lowermost mantle. © 2018 Elsevier B.V.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109934
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Laboratory of Seismology and Physics of Earth's Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China; Center for Advanced Radiation Sources, University of Chicago, Chicago, IL, United States
Recommended Citation:
Sun N.,Wei W.,Han S.,et al. Phase transition and thermal equations of state of (Fe,Al)-bridgmanite and post-perovskite: Implication for the chemical heterogeneity at the lowermost mantle[J]. Earth and Planetary Science Letters,2018-01-01,490