DOI: 10.1016/j.epsl.2018.09.014
Scopus记录号: 2-s2.0-85053815310
论文题名: Melting behavior of the lower-mantle ferropericlase across the spin crossover: Implication for the ultra-low velocity zones at the lowermost mantle
作者: Fu S. ; Yang J. ; Zhang Y. ; Liu J. ; Greenberg E. ; Prakapenka V.B. ; Okuchi T. ; Lin J.-F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 503 起始页码: 1
结束页码: 9
语种: 英语
英文关键词: ferropericlase
; lower mantle
; melting behavior
; spin crossover
Scopus关键词: Chemical analysis
; Energy dispersive spectroscopy
; Ion beams
; Iron
; Iron compounds
; Melting
; Molten materials
; Solid solutions
; Thermodynamics
; Ferropericlase
; Laser-heated diamond anvil cells
; Lower mantle
; Melting and crystallization
; Melting behavior
; Physical and chemical properties
; Spin crossovers
; Synchrotron x ray diffraction
; Magnesium compounds
; crystallization
; experimental mineralogy
; lower mantle
; magnesiowustite
; melting
; P-T conditions
; partitioning
; physicochemical property
; solid solution
英文摘要: Preferential iron partitioning into melt during melting and crystallization of lower mantle minerals – bridgmanite and ferropericlase – can play a critical role in our understanding of the origin of the early Earth and its evolution to form chemically and seismically distinct regions in the present lowermost mantle. Of particular interest is the consequence of iron spin crossover in ferropericlase on the physical and chemical properties of the molten materials under relevant pressure–temperature (P–T) conditions of the lowermost mantle. However, the spin crossover in liquid (Mg, Fe)O and its effects on melting curves, iron partitioning, melt density – and thus the evolution of an early basal magma ocean – remain poorly studied. Here we conducted high P–T melting experiments on ferropericlase with a starting composition of (Mg0.86Fe0.14)O using synchrotron X-ray diffraction up to ∼120 GPa and ∼5400 K in laser-heated diamond anvil cells, together with chemical analyses on quenched samples using focused ion beam and energy dispersive spectroscopy technique. An ideal solid solution model could be satisfactorily used to fit the experimental data of the liquidus and solidus of (Mg, Fe)O for pure high-spin (HS, below ∼83 GPa), and low-spin (LS, above ∼120 GPa) states, respectively. The experimental solidus and liquidus at 99 GPa and ∼4000–5200 K strongly deviate from ideal solid solution behavior for pure HS and LS states alone, but can be qualitatively explained using a thermodynamics model for a mixture of HS and LS states across the spin crossover. We found that LS (Mg, Fe)O exhibits ∼6–8% lower solidus and liquidus temperature than its HS counterpart. Furthermore, our results show that iron preferentially partitions into melt within the spin crossover to generate iron-rich LS melt. Such iron-rich LS (Mg, Fe)O is ∼27(±5)% denser than materials expected for lowermost mantle and could potentially persist as residual melt in the lowermost mantle at the late stage of magma ocean crystallization. Modeled results indicate that the existence of the dense, iron-rich LS (Mg, Fe)O melt in the lowermost mantle could provide plausible explanations for characteristic seismological signatures of ultra-low velocity zones (ULVZs). © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109626
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: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX78712, United States; Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai, 201900, China; Center for Advanced Radiation Sources, University of ChicagoIL, United States; Institute for Planetary Materials, Okayama University, Japan
Recommended Citation:
Fu S.,Yang J.,Zhang Y.,et al. Melting behavior of the lower-mantle ferropericlase across the spin crossover: Implication for the ultra-low velocity zones at the lowermost mantle[J]. Earth and Planetary Science Letters,2018-01-01,503