TY - JOUR
T1 - Melting behavior of the lower-mantle ferropericlase across the spin crossover
T2 - Implication for the ultra-low velocity zones at the lowermost mantle
AU - Fu, Suyu
AU - Yang, Jing
AU - Zhang, Youjun
AU - Liu, Jiachao
AU - Greenberg, Eran
AU - Prakapenka, Vitali B.
AU - Okuchi, Takuo
AU - Lin, Jung Fu
N1 - Funding Information:
The authors thank H. Yang for their assistance on the data collection of XRD spectra at 13IDD, GSECARS. We acknowledge D. Huang, Y. Wang and Z.L. Fan for the FIB/EDS analysis, and T. Tomioka for sample synthesis and analyses. The authors also thank R.H. Roberts for language polishing and S. Grand for the constructive suggestions and discussions. J.F.L. acknowledges support from the Geophysics and CSEDI Programs of the U.S. National Science Foundation (NSF), Deep Carbon Observatory (DCO) of the Alfred P. Sloan Foundation, Visiting Professorship of the Okayama University, and Center for High Pressure Science and Technology Advanced Research (HPSTAR). Y.Z. acknowledges support from the National Natural Science Foundation of China (41804082). High P−T melting experiments were conducted at GeoSoilEnviroCARS of APS, ANL. GeoSoilEnviroCARS operations are supported by the National Science Foundation-Earth Sciences (EAR-1128799) and the U.S. Department of Energy, Geosciences (DE-FG02-94ER14466).
Funding Information:
The authors thank H. Yang for their assistance on the data collection of XRD spectra at 13IDD, GSECARS. We acknowledge D. Huang, Y. Wang and Z.L. Fan for the FIB/EDS analysis, and T. Tomioka for sample synthesis and analyses. The authors also thank R.H. Roberts for language polishing and S. Grand for the constructive suggestions and discussions. J.F.L. acknowledges support from the Geophysics and CSEDI Programs of the U.S. National Science Foundation (NSF), Deep Carbon Observatory (DCO) of the Alfred P. Sloan Foundation , Visiting Professorship of the Okayama University, and Center for High Pressure Science and Technology Advanced Research (HPSTAR). Y.Z. acknowledges support from the National Natural Science Foundation of China ( 41804082 ). High P − T melting experiments were conducted at GeoSoilEnviroCARS of APS, ANL . GeoSoilEnviroCARS operations are supported by the National Science Foundation -Earth Sciences ( EAR-1128799 ) and the U.S. Department of Energy , Geosciences ( DE-FG02-94ER14466 ).
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/12/1
Y1 - 2018/12/1
N2 - 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).
AB - 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).
KW - ferropericlase
KW - lower mantle
KW - melting behavior
KW - spin crossover
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U2 - 10.1016/j.epsl.2018.09.014
DO - 10.1016/j.epsl.2018.09.014
M3 - Article
AN - SCOPUS:85053815310
SN - 0012-821X
VL - 503
SP - 1
EP - 9
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
ER -