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| Titel |
Magma flow directions inferred by AMS in regional dikes of Iceland |
| VerfasserIn |
P. Eriksson, F. Sigmundsson, S.-Å. Elming |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029969
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| Zusammenfassung |
| The extinguished and exhumed volcanic systems in the Tertiary bedrock
of Iceland provide unique exposures into central volcano complexes and
associated regional dike swarms. The regional dikes generated at the
time of intrusion substantial plate-spreading. In 2007 and 2008, a
number of 37 of these regional dikes near the east and west coast of
Iceland were sampled for analysis using anisotropy of magnetic
susceptibility (AMS). The aim was to infer flow directions in dikes
and contribute to a better understanding of dike intrusions in
volcanic systems. Dikes where the original contact with host rock
could be identified on both sides of the dikes were selected for the
study. The margins were sampled with a sample density of 8-9 samples
from each side at a distance of 10-20 cm from the chilled contact. At
this distance imbricated structures are expected to form in
simple-shear regions for several of the flow velocity models, as long
as the flow is laminar. The anisotropy of magnetic susceptibility of
the rock samples was used as a proxy for bulk mineral fabric. The
minor susceptibility axis were interpreted to lie normal to the flow
plane. Of the in total 37 dikes only 13 (35%) yielded results where
the minor susceptibility axis were perpendicular to the dike walls in
both the margins, a prerequisite for the flow-model used. Of the 13
dikes flow was defined in 12. Five dikes carried horizontal flow where
as the other seven carried vertical flows. Possible transtensive
shear-features was also found. The results show that magma flow in the
sampled regional dikes in Iceland, at a depth of 1-2 km from the
original surface varied from one dike to another, with vertical flow
of magma in some dikes and sub-horizontal flow of magma in others. |
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