DOI: 10.1016/j.epsl.2020.116358
论文题名: Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle
作者: Heyn B.H. ; Conrad C.P. ; Trønnes R.G.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 543 语种: 英语
中文关键词: core-mantle boundary topography
; dynamic topography
; large low shear velocity provinces
; mantle plumes
; mantle structure
; thermochemical piles
英文关键词: Boundary layers
; Shear flow
; Structural geology
; Topography
; Viscosity
; Core-mantle boundary
; Density structures
; Dynamic topography
; Intrinsic viscosity
; Large Low Shear Velocity Provinces (LLSVPs)
; Seismic velocities
; Thermal boundary layer
; Viscosity contrast
; Piles
; boundary layer
; core-mantle boundary
; lower mantle
; mantle structure
; pile
; seismic velocity
; topography
; viscosity
英文摘要: Two large areas of anomalously low seismic velocities are visible in all tomographic models of the lowermost mantle. Depending on the density structure of these Large Low Shear Velocity Provinces (LLSVPs), the core-mantle boundary (CMB) will deform upwards or downwards due to isostatic and dynamic topography, the latter being sensitive to the viscosity structure of the lowermost mantle. Heterogeneities in the viscosity structure, although difficult to constrain, might be especially important if the LLSVPs are thermochemical piles with elevated intrinsic viscosity as suggested by mineral physics. Based on numerical models, we identify a short-wavelength (about 80-120 km wide, up to a few km deep) topographic depression that forms around the pile edges if the pile is more viscous than the surrounding mantle. The depression forms when a wedge of thermal boundary layer material becomes compressed against the viscous pile, and is enhanced by relative uplift of the CMB beneath the pile by plumes rising above it. The depth and asymmetry of the depression constrain the magnitude of the viscosity contrast between pile and the surrounding mantle. Furthermore, (periodic) plume initiation and pile collapse at the pile margin systematically modify the characteristic depression, with a maximum in asymmetry and depth at the time of plume initiation. Core-reflected waves or scattered energy may be used to detect this topographic signature of stiff thermochemical piles at the base of the mantle. © 2020 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165023
Appears in Collections: 气候变化与战略
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作者单位: Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Norway; Natural History Museum, University of Oslo, Norway
Recommended Citation:
Heyn B.H.,Conrad C.P.,Trønnes R.G.. Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle[J]. Earth and Planetary Science Letters,2020-01-01,543