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Mesozoic rift magmatism in the North Sea region: Ar-40/Ar-39 geochronology of Scanian basalts and geochemical constraints

Bergelin, Ingemar LU ; Obst, Karsten; Söderlund, Ulf LU ; Larsson, Kent LU and Johansson, Leif LU (2011) In International Journal of Earth Sciences 100(4). p.787-804
Abstract
More than 100 volcanic necks composed of basanites and melanephelinites occur in Scania, southern Sweden, at the junction of two major tectonic lineaments, the Phanerozoic Sorgenfrei-Tornquist Zone (STZ) and the Proterozoic Protogine Zone. New Ar-40/Ar-39 isotope analyses of whole rock fragments of nine selected basalt necks suggest that the Mesozoic alkaline volcanism in the Scanian province commenced earlier than previously reported and comprised three separate volcanic episodes that span a total period of ca. 80 Myr: a first Jurassic (191-178 Ma), a second at the Jurassic/Cretaceous boundary (ca. 145 Ma), and a final middle Cretaceous episode (ca. 110 Ma). The new results allow for precise time correlations between eruption events in... (More)
More than 100 volcanic necks composed of basanites and melanephelinites occur in Scania, southern Sweden, at the junction of two major tectonic lineaments, the Phanerozoic Sorgenfrei-Tornquist Zone (STZ) and the Proterozoic Protogine Zone. New Ar-40/Ar-39 isotope analyses of whole rock fragments of nine selected basalt necks suggest that the Mesozoic alkaline volcanism in the Scanian province commenced earlier than previously reported and comprised three separate volcanic episodes that span a total period of ca. 80 Myr: a first Jurassic (191-178 Ma), a second at the Jurassic/Cretaceous boundary (ca. 145 Ma), and a final middle Cretaceous episode (ca. 110 Ma). The new results allow for precise time correlations between eruption events in the Scanian and those in the North Sea volcanic provinces. The older, early Jurassic event in Scania is largely synchronous with that in the Egersund Basin and the Forties field whereas the event at ca. 145 Ma is correlated with activity in the Central Graben. These volcanic episodes also correlate in age with Kimmerian tectonic activity. Volcanic activity in the middle Cretaceous period has also been dated in the triple junction in the North Sea and offshore in the Netherland Sector. The correlation of basalt volcanism in Scania with the Egersund nephelinites strongly suggest that volcanism was triggered by repeated tectonic activity along the STZ. Geochemical data of alkaline mafic rocks in the Scanian and the North Sea volcanic provinces imply that different provinces have largely unique geochemical signatures in favour of a heterogeneous mantle in the North Sea volcanic region. However, basalts of different generations in one and the same province cannot be readily separated on the basis of geochemistry, suggesting that the same lithospheric mantle was the source of repeated volcanism over time in each province. The data suggest a low degree of melting of a volatile-bearing mantle lherzolite enriched in incompatible elements with the exception of the Forties basalts in the rift centre, produced by larger degree of melting and evolved by fractional crystallization. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Alkaline basalt, Geochronology, Mesozoic, North Sea, Rift magmatism, Scanian volcanic province
in
International Journal of Earth Sciences
volume
100
issue
4
pages
787 - 804
publisher
Springer
external identifiers
  • wos:000290036300005
  • scopus:79955567893
ISSN
1437-3254
DOI
10.1007/s00531-010-0516-3
language
English
LU publication?
yes
id
85d97ba0-b4d6-4deb-9457-fc126a257a6a (old id 1987837)
date added to LUP
2011-06-29 09:02:04
date last changed
2017-01-01 04:03:54
@article{85d97ba0-b4d6-4deb-9457-fc126a257a6a,
  abstract     = {More than 100 volcanic necks composed of basanites and melanephelinites occur in Scania, southern Sweden, at the junction of two major tectonic lineaments, the Phanerozoic Sorgenfrei-Tornquist Zone (STZ) and the Proterozoic Protogine Zone. New Ar-40/Ar-39 isotope analyses of whole rock fragments of nine selected basalt necks suggest that the Mesozoic alkaline volcanism in the Scanian province commenced earlier than previously reported and comprised three separate volcanic episodes that span a total period of ca. 80 Myr: a first Jurassic (191-178 Ma), a second at the Jurassic/Cretaceous boundary (ca. 145 Ma), and a final middle Cretaceous episode (ca. 110 Ma). The new results allow for precise time correlations between eruption events in the Scanian and those in the North Sea volcanic provinces. The older, early Jurassic event in Scania is largely synchronous with that in the Egersund Basin and the Forties field whereas the event at ca. 145 Ma is correlated with activity in the Central Graben. These volcanic episodes also correlate in age with Kimmerian tectonic activity. Volcanic activity in the middle Cretaceous period has also been dated in the triple junction in the North Sea and offshore in the Netherland Sector. The correlation of basalt volcanism in Scania with the Egersund nephelinites strongly suggest that volcanism was triggered by repeated tectonic activity along the STZ. Geochemical data of alkaline mafic rocks in the Scanian and the North Sea volcanic provinces imply that different provinces have largely unique geochemical signatures in favour of a heterogeneous mantle in the North Sea volcanic region. However, basalts of different generations in one and the same province cannot be readily separated on the basis of geochemistry, suggesting that the same lithospheric mantle was the source of repeated volcanism over time in each province. The data suggest a low degree of melting of a volatile-bearing mantle lherzolite enriched in incompatible elements with the exception of the Forties basalts in the rift centre, produced by larger degree of melting and evolved by fractional crystallization.},
  author       = {Bergelin, Ingemar and Obst, Karsten and Söderlund, Ulf and Larsson, Kent and Johansson, Leif},
  issn         = {1437-3254},
  keyword      = {Alkaline basalt,Geochronology,Mesozoic,North Sea,Rift magmatism,Scanian volcanic province},
  language     = {eng},
  number       = {4},
  pages        = {787--804},
  publisher    = {Springer},
  series       = {International Journal of Earth Sciences},
  title        = {Mesozoic rift magmatism in the North Sea region: Ar-40/Ar-39 geochronology of Scanian basalts and geochemical constraints},
  url          = {http://dx.doi.org/10.1007/s00531-010-0516-3},
  volume       = {100},
  year         = {2011},
}