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Plume-driven plumbing and crustal formation in Iceland

Allen, R.M.; Nolet, G.; Morgan, W.J.; Vogfjörd, K.; Nettles, M.; Ekström, G.; Bergsson, B.H.; Erlendsson, P.; Foulger, G.R.; Jakobsdóttir, S.; Julian, B.R.; Pritchard, M.J.; Ragnarsson, S.; Stefánsson, R.

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Authors

R.M. Allen

G. Nolet

W.J. Morgan

K. Vogfjörd

M. Nettles

G. Ekström

B.H. Bergsson

P. Erlendsson

G.R. Foulger

S. Jakobsdóttir

B.R. Julian

M.J. Pritchard

S. Ragnarsson

R. Stefánsson



Abstract

Through combination of surface wave and body wave constraints we derive a three-dimensional (3-D) crustal S velocity model and Moho map for Iceland. It reveals a vast plumbing system feeding mantle plume melt into upper crustal magma chambers where crustal formation takes place. The method is based on the partitioned waveform inversion to which we add additional observations. Love waves from six local events recorded on the HOTSPOT- SIL networks are fitted, Sn travel times from the same events measured, previous observations of crustal thickness are added, and all three sets of constraints simultaneously inverted for our 3-D model. In the upper crust (0–15 km) an elongated low-velocity region extends along the length of the Northern, Eastern and Western Neovolcanic Zones. The lowest velocities (−7%) are found at 5–10 km below the two most active volcanic complexes: Hekla and Bárdarbunga-Grímsvötn. In the lower crust (>15 km) the low-velocity region can be represented as a vertical cylinder beneath central Iceland. The low-velocity structure is interpreted as the thermal halo of pipe work which connects the region of melt generation in the uppermost mantle beneath central Iceland to active volcanoes along the neovolcanic zones. Crustal thickness in Iceland varies from 15–20 km beneath the Reykjanes Peninsula, Krafla and the extinct Snæfellsnes rift zone, to 46 km beneath central Iceland. The average crustal thickness is 29 km. The variations in thickness can be explained in terms of the temporal variation in plume productivity over the last ∼20 Myr, the Snæfellsnes rift zone being active during a minimum in plume productivity. Variations in crustal thickness do not depart significantly from an isostatically predicted crustal thickness. The best fit linear isostatic relation implies an average density jump of 4% across the Moho. Rare earth element inversions of basalt compositions on Iceland suggest a melt thickness (i.e., crustal thickness) of 15–20 km, given passive upwelling. The observed crustal thickness of up to 46 km implies active fluxing of source material through the melt zone by the mantle plume at up to 3 times the passive rate.

Citation

Allen, R., Nolet, G., Morgan, W., Vogfjörd, K., Nettles, M., Ekström, G., …Stefánsson, R. (2002). Plume-driven plumbing and crustal formation in Iceland. Journal of Geophysical Research, 107(B8), Article 2163. https://doi.org/10.1029/2001jb000584

Journal Article Type Article
Publication Date Aug 1, 2002
Deposit Date Feb 27, 2015
Publicly Available Date Feb 27, 2015
Journal Journal of Geophysical Research. Solid Earth
Print ISSN 0148-0227
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 107
Issue B8
Article Number 2163
DOI https://doi.org/10.1029/2001jb000584
Keywords Oceanic crust, Iceland, Tomography, Crustal formation, Melt migration, Not spot.
Public URL https://durham-repository.worktribe.com/output/1620680

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Copyright Statement
Allen, R.M., Nolet, G., Morgan, W.J., Vogfjörd, K., Nettles, M., Ekström, G., Bergsson, B.H., Erlendsson, P., Foulger, G.R., Jakobsdóttir, S., Julian, B.R., Pritchard, M.J., Ragnarsson, S. and Stefánsson, R., (2002), Plume-driven plumbing and crustal formation in Iceland, Journal of Geophysical Research: Solid Earth, 107, 2163, 10.1029/2001JB000584 (DOI). To view the published open abstract, go to http://dx.doi.org and enter the DOI.





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