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DOI	10.1016/j.epsl.2020.116358
	Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle
	Heyn B.H.; Conrad C.P.; Trønnes R.G.
发表日期	2020
ISSN	0012821X
卷号	543
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)
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
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202645
作者单位	Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Norway; Natural History Museum, University of Oslo, Norway
推荐引用方式 GB/T 7714	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],2020,543.
APA	Heyn B.H.,Conrad C.P.,&Trønnes R.G..(2020).Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle.Earth and Planetary Science Letters,543.
MLA	Heyn B.H.,et al."Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle".Earth and Planetary Science Letters 543(2020).