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| Titel |
Continental hyperextension, mantle exhumation and thin oceanic crust at the continent-ocean transition, West Iberia: new insights from wide-angle seismic |
| VerfasserIn |
Richard Davy, Tim Minshull, Gaye Bayrakci, Jon Bull, Dirk Klaeschen, Cord Papenberg, Timothy Reston, Dale Sawyer, Colin Zelt |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127949
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| Publikation (Nr.) |
 EGU/EGU2016-7881.pdf |
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| Zusammenfassung |
| Anomalously thin oceanic crust and expanses of exhumed and serpentinised mantle material
at magma-poor rift margins are now a globally observed phenomena that characterizes the
seaward limit of the continent-ocean transition. Hyperextension of continental crust at the
Deep Galicia rifted margin in the North Atlantic has been accommodated by the rotation of
continental fault blocks, which are underlain by the S-reflector, an interpreted detachment
fault, along which exhumed and serpentinized mantle peridotite is observed. West of these
features, the enigmatic Peridotite Ridge has been suggested to delimit the seaward extent of
the continent-ocean transition. An outstanding question at this margin is where oceanic crust
begins, with little existing data to constrain this boundary and a lack of clear seafloor
spreading magnetic anomalies. Here we present results from a 160-km-long wide-angle
seismic profile (WE-1). Forward modelling and travel time tomography models of the crustal
compressional velocity structure reveal highly thinned and rotated crustal blocks
overlying the S-reflector, which correlates with the 6.0 – 7.0 kms−1 velocity contours,
corresponding to peridotite serpentinization of 60 – 30 %, respectively. West of the
Peridotite Ridge we observe a basement layer which is 2.8 - 3.5 km thick in which
velocities increase smoothly and rapidly from ∼4.6 kms−1 to 7.3 - 7.6 kms−1,with
an average velocity gradient of 1.00 s−1. Below this, velocities slowly increase
toward typical mantle velocities. Such a downward increase into mantle velocities is
interpreted as decreasing serpentinization of mantle material with depth. However, sparse
Moho reflections indicate the onset of an anomalously thin oceanic crust, which
increases in thickness from ∼0.5 km to ∼1.5 km over a distance of 35 km, seaward. |
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