DOI: 10.1016/j.epsl.2021.116973
论文题名: The miscibility of calcium silicate perovskite and bridgmanite: A single perovskite solid solution in hot, iron-rich regions
作者: Muir J.M.R. ; Thomson A.R. ; Zhang F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 566 语种: 英语
中文关键词: bridgmanite
; calcium silicate perovskite
; phase mixing
英文关键词: Calcium silicate
; Iron
; Molecular dynamics
; Perovskite
; Seismology
; Silicates
; Solid solutions
; Solubility
; Bridgmanite
; Calcium silicate perovskite
; Geochemicals
; Iron rich
; Lower mantle
; Perovskite solid solutions
; Phase mixing
; Silicate perovskite
; Single phase
; Two phase
; Mixing
; calcium
; concentration (composition)
; mantle chemistry
; mixing
; perovskite
; silicate
; solid solution
英文摘要: Calcium silicate perovskite and bridgmanite are two phases believed to coexist throughout the lower mantle, which at some temperature, at least theoretically, dissolve into each other to form a single perovskite solid solution (CaxMg1−xSiO3). This may have large seismic and geochemical implications due to the changes in density, elasticity and element partition coefficients between single and mixed phase perovskites. DFT Molecular Dynamics has been used to estimate the miscibility of bridgmanite and calcium perovskite at pressures between 25 and 125 GPa. At 125 GPa (where mixing is the greatest in our pressure range) to mix 1% of Ca-pv into bridgmanite requires a temperature of 2042 K, 5% 2588 K, 10% 2675 K and 50% 2743 K. Therefore, in a simplified lower mantle chemistry an extensive MgSiO3–CaSiO3 solid solution is not expected to occur. However, a simple model was employed to test whether the presence of other elements might influence this mutual solid solution and it was demonstrated that if sufficient concentrations (>1 at.%) of additional elements are present then miscibility may become favourable. Of the elements likely to be present at these concentrations it appears that ferrous iron promotes, whilst aluminium inhibits, a single-phase perovskite solid solution. To a lesser extent ferric iron may both increase and decrease perovskite miscibility. Modelling for realistic mantle compositions suggests that basaltic lithologies will always retain two perovskite components, whereas a single perovskite solid solution may be preferred in hot and/or iron-rich pyrolytic bulk compositions near the base of the lower mantle. Static calculations indicate perovskite miscibility may cause pyrolytic lithologies (with 12.5% CaSiO3) to possess lower density (−0.14–0.25%), Vs (−1.5–3.5%) and Vp (−0.5–1.2%), and higher VΦ (+ 0.00–0.75%) than predicted for assemblages containing two perovskites. These seismic changes, while preliminary, are similar to those observed in the LLSVPs which are also regions that are likely hotter than the surrounding mantle and thus possess conditions promoting the formation of a single perovskite phase. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165610
Appears in Collections: 气候变化与战略
There are no files associated with this item.
作者单位: State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 99 West Lincheng Road, Guiyang, Guizhou 50081, China; Department of Earth Sciences, University College London, London, WC1E 6BT, United Kingdom
Recommended Citation:
Muir J.M.R.,Thomson A.R.,Zhang F.. The miscibility of calcium silicate perovskite and bridgmanite: A single perovskite solid solution in hot, iron-rich regions[J]. Earth and Planetary Science Letters,2021-01-01,566