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Durham University

Department of Earth Sciences

Current Postgraduate Students

Publication details for Prof Gillian Foulger

Du, Z, Vinnik, L.P & Foulger, G.R. (2006). Evidence from P-to-S mantle converted waves for a flat “660-km” discontinuity beneath Iceland. Earth and Planetary Science Letters 241(1-2): 271-280.

Author(s) from Durham

Abstract

Iceland is the type example of a ridge-centered hotspot. It is controversial whether the seismic anomaly beneath it originates in the lower mantle or the upper mantle. Some recent studies reported that the 660-km discontinuity beneath central Iceland is shallow relative to peripheral regions and this was interpreted as an effect of elevated temperature at that depth. We investigate topography of the major upper mantle discontinuities by separating the effects of the topography and volumetric velocity heterogeneity in P receiver functions from 55 seismograph stations. Our analysis demonstrates that a significant (at least 10-km) shallowing of the 660-km discontinuity is only possible in the case of improbably low seismic velocities in the mantle transition zone beneath central Iceland. If, as in previous studies, lateral velocity variations in the mantle transition zone are neglected, the data require a depressed rather than an uplifted 660-km discontinuity. For a reasonable S-wave velocity anomaly in the mantle transition zone (around − 3%) no topography on the 660-km discontinuity is required. This can be explained by the lack of temperature anomaly or an effect of two phase transitions with opposite Clapeyron slopes.

References

1

V. Courtillot, A. Davaillie, J. Besse, J. Stock, Three distinct
types of hotspots in the Earth’s mantle, Earth Planet Sci. Lett.
(2003) 295–308.

2

D.L. Anderson, The thermal state of the upper mantle; no
role for mantle plumes, Geophys. Res. Lett. 27 (2000)
3623– 3626.

3

G.R. Foulger, M.J. Pritchard, B.R. Julian, J.R. Evans, R.M.
Allen, G. Nolet, W.J. Morgan, B.H. Bergsson, P. Erlendsson,
S. Jakobsdottir, S. Ragnarsson, R. Stefansson, K. Vogfjord,
The seismic anomaly beneath Iceland extends down to the
mantle transition zone and no deeper, Geophys. J. Int. 142
(2000) F1–F5 (Fast Track).

4

I.T. Bjarnason, W. Menke, O.G. Flovenz, D. Caress, Tomographic
image of the mid-Atlantic plate boundary in southwestern
Iceland, J. Geophys. Res. 98 (1993) 6607– 6622.

5

C.J. Wolfe, I.T. Bjarnason, J.C. VanDecar, S.C. Solomon, Seismic
structure of the Iceland mantle plume, Nature 385 (1997)
245– 247.

6

F.A. Darbyshire, I.T. Bjarnason, R.S. White, O.G. Flovenz,
Crustal structure above the Iceland mantle plume imaged by
the ICEMELT refraction profile, Geophys. J. Int. 135 (1998)
1131–1149.

7

G.R. Foulger, M.J. Pritchard, B.R. Julian, J.R. Evans, R.M. Allen,
G. Nolet,W.J. Morgan, B.H. Bergsson, P. Erlendsson, S. Jakobsdottir,
S. Ragnarsson, R. Stefansson, K. Vogfjord, Seismic tomography
shows that upwelling beneath Iceland is confined to the
upper mantle, Geophys. J. Int. 146 (2001) 504– 530.

8

Z. Du, G.R. Foulger, Surface wave waveform inversion for
variation in upper mantle structure beneath Iceland, Geophys.
J. Int. 157 (2004) 305– 314.

9

R.M. Allen, G. Nolet, W.J. Morgan, K. Vogfjord, B.H. Bergsson,
P. Erlendsson, G.R. Foulger, S. Jakobsdottir, B.R. Julian,
M.J. Pritchard, S. Ragnarsson, R. Stefansson, Imaging the mantle
beneath Iceland using integrated seismological techniques,
J. Geophys. Res. 107 (B12) (2002), doi:10.1029/2001JB000595.

10

J. Ritsema, H.J. van Heijst, J.H. Woodhouse, Complex shear
wave velocity structure imaged beneath Africa and Iceland,
Science 286 (1999) 1925– 1928.

11

R. Montelli, G. Nolet, F.A. Dahlen, G. Masters, R.E. Engdahl,
S.-H. Hung, Finite frequency tomography reveals a variety of
plumes in the mantle, Science 303 (2004) 338– 343.

12

V. Farra, L. Vinnik, Upper mantle stratification by P and S
receiver functions, Geophys. J. Int. 141 (2000) 699–712.

13

T. Katsura, E. Ito, The system Mg2SiO4–Fe2SiO4 at high pressures
and temperatures: Precise determination of stabilities of
olivine, modified spinel, and spinel, J. Geophys. Res. 94 (1989)
15633– 15670.

14

E. Ito, E. Takahasi, Postspinel transformations in the system
Mg2SiO4–Fe2SiO4 and some geophysical implications, J. Geophys.
Res. 94 (1989) 10646–10673.

15

K. Hirose, Phase transitions in pyrolitic mantle around 670-
km depth: implications for upwelling of plumes from the
lower mantle, J. Geophys. Res. 107 (2002), doi:10.1029/
2001JB000595.

16

Y. Shen, S.C. Solomon, I.T. Bjarnason, G.M. Purdy, Hot
mantle transition zone beneath Iceland and the adjacent
mid-Atlantic Ridge inferred from P-to-S conversions at the
410- and 660-km discontinuities, Geophys. Res. Lett. 23
(1996) 3527– 3530.

17

Y. Shen, S.C. Solomon, I.T. Bjarnason, C.J. Wolfe, Seismic
evidence for a lower-mantle origin of the Iceland plume, Nature
395 (6697) (1998) 62– 65.

18

Y. Shen, S.C. Solomon, I.T. Bjarnason, G. Nolet, W.J. Morgan,
R.M. Allen, K. Vogfjord, S. Jakobsdottir, R. Stefansson, B.R.
Julian, G.R. Foulger, Seismic evidence for a tilted mantle plume
and north–south mantle flow beneath Iceland, Earth Planet. Sci.
Lett. 197 (2002) 261–272.

19

L.P. Vinnik, Detection of waves converted from P to SV in the
mantle, Phys. Earth Planet. Inter. 15 (1977) 39– 45.

20

R. Stefansson, Earthquake prediction research in the south Iceland
seismic zone and the SIL project, Bull. Seismol. Soc. Am.
83 (1993) 696–716.

21

G.R. Foulger, Z. Du, B.R. Julian, Icelandic-type crust, Geophys.
J. Int. 155 (2003) 567–590.

22

B. Efron, R. Tibshirani, Statistical data analysis in the computer
age, Science 253 (1991) 390– 395.

23

S. Pilidou, K. Priestley, E. De bayle, O. Gudmundsson, Rayleigh
wave tomography in the North Atlantic: high resolution images
of the Iceland, Azores and Eifel mantle plumes, Lithos 79 (2005)
453–474.

24

B.L.N. Kennett, E.R. Engdahl, Travel times for global earthquake
location and phase identification, Geophys. J. Int. 105
(1991) 429–466.

25

S.L. Chevrot, L. Vinnik, J.-P. Montagner, Global scale analysis
of the mantle Pds phases, J. Geophys. Res. 104 (1999)
20203– 20219.

26

L. Vinnik, S. Chevrot, J.-P. Montagner, F. Guyot, Teleseismic
travel time residuals in North America and anelasticity
of the asthenosphere, Phys. Earth Planet. Inter. 116 (1999)
93–103.

27

S. Karato, Importance of anelasticity in the interpretation
of seismic tomography, Geophys. Res. Lett. 20 (1993)
1623–1626.

28

L.P. Vinnik, G.R. Foulger, Z. Du, Seismic boundaries in the
mantle beneath Iceland: a new constraint on temperature, Geophys.
J. Int. 160 (2005) 533– 538.

29

D.C. Presnall, Phase Diagrams of Earth-forming Minerals,
in Mineral Physics and Crystallography: A Handbook of
Physical Constants, American Geophysical Union, Washington,
DC, 1995.