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| Titel |
Caught in the Act: Crustal Manifestations of a Hot Transient Pulse Beneath the Mid-Atlantic Ridge at 60°N |
| VerfasserIn |
Ross Parnell-Turner, Nicky White, Tim Henstock, Bramley J. Murton, Stephen Jones, John Maclennan |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072927
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| Zusammenfassung |
| Since its inception, mantle convective upwelling beneath Iceland has had a significant
influence on the history of vertical motion, magmatism and paleoceanography in the North
Atlantic Ocean. Crucially, intersection of the Reykjanes Ridge with the Icelandic plume
provides us with an important window into the transient activity of the plume. The spreading
ridge acts as a linear sampler of plume activity, which is recorded as a series of
time-transgressive V-shaped ridges and troughs. Here, we present the results of a
detailed study along the spreading ridge close to 60°N, where the youngest V-shaped
ridge of thickened oceanic crust, is forming today. A combination of multibeam
bathymetry and seismic reflection profiles, acquired along and across the ridge axis, is
used to map the detailed pattern of volcanism and normal faulting. Along the ridge
axis, the density of volcanic seamounts varies markedly, increasing by a factor of
two between 59° and 62°N. Within this area, seismic imaging shows that there is
enhanced acoustic scattering at the seabed. These observations are accompanied by a
decrease in mean fault length from ~12 km to ~6 km. A 1960–2009 catalog of
relocated teleseismic earthquake hypocenters shows that there is a pronounced gap in
seismicity between 59° and 62°N where the cumulative moment release is two
orders of magnitude smaller than that along adjacent ridge segments. A steady-state
thermal model is used to show that a combination of increased melt generation and
decreased hydrothermal circulation accounts for this suite of observations. Our
results suggest that the thickness of the brittle seismogenic layer is smaller where
the youngest V-shaped ridge intersects the ridge axis. This decrease is consistent
with geochemical modeling of dredged basaltic samples, which require horizontal
flow of hotter asthenospheric material within a channel beneath the spreading axis.
Thus, along-axis variation in melt supply arising from the passage of a pulse of
hot material directly affects crustal accretion processes and rheological properties. |
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