DOI: 10.1016/j.epsl.2020.116600
论文题名: Global variations of Earth's 520- and 560-km discontinuities
作者: Tian D. ; Lv M. ; Wei S.S. ; Dorfman S.M. ; Shearer P.M.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 552 语种: 英语
中文关键词: 520-km discontinuity
; 560-km discontinuity
; mantle phase transformations
; mantle transition zone
; oceanic crust recycling
; SS precursors
英文关键词: Calcium
; Garnets
; Seismology
; Calcium perovskite
; Cold subduction
; Compositional heterogeneity
; Global existence
; Global variations
; Mantle transition zone
; Seismic discontinuities
; Seismic observation
; Perovskite
; calcium
; concentration (composition)
; discontinuity
; mantle structure
; oceanic crust
; perovskite
; seismic method
; subduction zone
英文摘要: We investigate seismic discontinuities in the mantle transition zone (MTZ) by analyzing SS precursors recorded at global seismic stations. Our observations confirm the global existence of the 520-km discontinuity. Although substantial regional depth variations in the 520-km discontinuity are generally correlated with temperature in the mid-MTZ, they cannot be fully explained by the Clapeyron slope of the wadsleyite-ringwoodite phase transition, suggesting both thermal and compositional heterogeneities in the MTZ. A second discontinuity at ∼560-km depth, previously interpreted as splitting of the 520-km discontinuity, is most commonly detected in cold subduction zones and hot mantle regions. The depth separation between the 520- and 560-km discontinuities varies from ∼80 km in cold regions to ∼40 km in hot areas. The exsolution of calcium-perovskite (Ca-pv) from majorite garnet has been proposed to explain the velocity and density changes across the 560-km discontinuity. However, the gradual exsolution of perovskite and partitioning of Ca and Al between perovskite and garnet appear inconsistent with the relatively “sharp” discontinuity in seismic observations and thus need to be revisited in the future. Nevertheless, because the only known transition in major minerals at this depth in the MTZ is the formation of Ca-pv, the existence of the 560-km discontinuity may imply localized high calcium concentrations in the mid-MTZ possibly related to the recycling of oceanic crust. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165312
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI 48824, United States; Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, United States
Recommended Citation:
Tian D.,Lv M.,Wei S.S.,et al. Global variations of Earth's 520- and 560-km discontinuities[J]. Earth and Planetary Science Letters,2020-01-01,552