DOI: 10.1016/j.epsl.2021.116813
论文题名: Global receiver function observations of the X-discontinuity reveal recycled basalt beneath hotspots
作者: Pugh S. ; Jenkins J. ; Boyce A. ; Cottaar S.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 561 语种: 英语
中文关键词: hotspot
; receiver function
; recycled basalt
; upper mantle
; X-discontinuity
英文关键词: Recycling
; Seismic waves
; Silica
; Silicates
; Chemical heterogeneities
; Global distribution
; High frequency HF
; Impedance contrast
; Mantle temperatures
; Mantle upwellings
; Receiver function observations
; Receiver functions
; Basalt
; basalt
; craton
; discontinuity
; heterogeneity
; hot spot
; magmatism
; mantle convection
; mantle plume
; P-wave
; seismic survey
; teleseismic wave
; upper mantle
; wavelength
英文摘要: The distribution of chemical heterogeneity beneath hotspots provides important constraints on the source of magmatism and mantle convection. Chemical heterogeneities in the upper mantle produce discontinuities that can be interrogated seismically. One such discontinuity, the X-discontinuity (230-350 km depth), is observed intermittently across the globe, with multiple possible causal mechanisms. However, to better understand the cause of the X-discontinuity and its relationship to mantle upwellings, we require global short wavelength observations, previously unresolved by reflected phases with broad upper mantle Fresnel zones. Discontinuities resulting from seismically observable impedance contrasts can be targeted using high frequency P wave receiver functions (RFs) possessing short wavelength lateral sensitivity (∼100 km) to structures almost directly beneath the station. Thus, below well-instrumented hotspots we can investigate the properties of the X-discontinuity and constrain the causal mechanisms in these locations. Using P-to-s converted teleseismic phases between 30-90∘, we stack RFs in the depth and time-slowness domains at 28 hotspots and 6 cratons globally. This reveals 15 robust X-discontinuity observations beneath hotspots between 244-344 km depth. A further 10 potential observations are present beneath hotspots, and 6 null observations beneath cratons. Two causal mechanisms remain possible at the elevated mantle temperatures expected beneath hotspots. The coesite-stishovite phase transition occurs in eclogite and/or carbonated silicate melt may form under certain conditions. For either mechanism to provide seismically observable impedance contrasts, the upper mantle must be locally enriched in basalt. Assessing the X-discontinuity global distribution reveals a correlation with the Large Low Velocity Provinces, suggesting that mantle plumes may entrain recycled basalt from the lowermost mantle. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165635
Appears in Collections: 气候变化与战略
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作者单位: Bullard Laboratories, Department of Earth Sciences, University of Cambridge, United Kingdom
Recommended Citation:
Pugh S.,Jenkins J.,Boyce A.,et al. Global receiver function observations of the X-discontinuity reveal recycled basalt beneath hotspots[J]. Earth and Planetary Science Letters,2021-01-01,561