 |
| Titel |
The extension of the Vøring margin (NE Atlantic) in case of different degrees of magmatic underplating |
| VerfasserIn |
Magnus Wangen, Rolf Mjelde, Jan Inge Faleide |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048051
|
|
|
|
|
|
| Zusammenfassung |
| The Vøring margin is a passive volcanic margin off-shore mid-Norway in the NE Atlantic.
The margin has gone through a history of several rift phases, where the last rift
phase ended with continental breakup and sea-floor spreading in the Early Tertiary.
Continental breakup was associated with high rates of magma generation and flood
basalts. The western part of the margin is characterized by a high velocity layer (Vp =
7.2 to 7.6 km/s) in the lower crust. The origin of this high velocity Lower Crustal
Body (LCB) is debated. The LCB is studied with three scenarios of its extension
history in order to learn more about its nature. The scenarios are: (a) The LCB is
Caledonian crust. (b) Half the LCB is Caledonian crust and the other half is emplaced as
magmatic underplating in Late Paleocene. (c) The entire LCB is emplaced as magmatic
underplating. The crustal extension is usually obtained with the backstripping procedure. A
problem with the backstripping procedure is that is does not account for the extension
and thinning of the sedimentary basin. This is in particular a problem for the deep
sub-basins of the Vøring margin, because the margin has gone through a history
of several rift phases with a substantial amount of rifting. The extension of the
margin transect is obtained with a procedure that accounts for the extension and
thinning of the sedimentary basins. This procedure also accounts for magmatic
underplating. The lithosphere is modeled with deposition of sediments and it involves four
rift phases since the Early Devonian until today. The forward modeling is mass
conservative and the present-day thicknesses of the formations, crust, LCB and
magmatic underplate are reproduced. The state of the lithosphere and the sedimentary
basins are shown and compared at the beginning and at the end of the rift phases.
It is concluded that the scenario with the LCB as only underplating requires an
unrealistic amount of extension. A more likely scenario lets underplating account for
maximum half the LCB. The modeling shows that the Late Jurassic rift phase was much
more prominent than the Late Cretaceous and Paleocene rift phase for all cases of
underplating. A strong Late Jurassic rift phase is consistent with the accumulation space
needed for the thick Cretaceous formations. There is no observations of magmatism
from the Late Jurassic, although this rift phase is stronger than the Cretaceous and
Paleocene rift phase. The modeling is based on a new interpretation of the Moho
underneath the Utgard High, which is taken to be deeper and flatter than previously
suggested. |
|
|
|
|
|
|