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| Titel |
Eurekan deformation on Prins Karls Forland, Svalbard – new insights from Ar40/Ar39 muscovite dating |
| VerfasserIn |
Karol Faehnrich, David Schneider, Maciej Manecki, Jerzy Czerny, Per Inge Myhre, Jarosław Majka, Karolina Kośmińska, Christopher Barnes, Maria Maraszewska |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137804
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| Publikation (Nr.) |
 EGU/EGU2017-642.pdf |
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| Zusammenfassung |
| Eurekan deformation has been proven to be a complex sequence of tectonic episodes,
dominated by compression in the Circum Arctic region. It was associated with early
Cenozoic collision of Eurasia, North America and Greenland plates producing fold-thrust belt
style of deformation. Timing of this enigmatic event has not yet been extensively resolved by
radiometric dating (Piepjohn et al. 2016, Journal of the Geological Society, 173(6),
1007-1024). Reinhardt et al. (2013, Z. Dt. Ges. Geowiss., 164 (1), 131–147) dated
syn-tectonic volcanic ashes at c. 60 Ma and 54 Ma on Ellesmere Island, Canada. Tagner et al.
(2011, Earth and Planetary Science Letters, 303(3), 203-214) interpreted c. 49-47 Ma
40Ar/39Ar ages on trachyte flows in northern Greenland as peak compression during the
Eurekan event. On Svalbard, Tessensohn et al. (2001, Geologisches Jahrbuch, B 91, 83-104)
reported K/Ar whole rock ages ranging from c. 67 to 49 Ma for the slates from
Svartfjella–Eidembukta–Daudmannsodden Lineament. Bentonite layers in the Central
Tertiary Basin are as young as c. 56 Ma (Charles et al. 2011, Geochem. Geophys.
Geosyst., 12, 1-19), predating latest deformation. Moreover, Barnes et al (2017, in
prep.) applied (U-Th)/He thermochronology along the western margin of Svalbard
and resolved Early to Middle Eocene heating, likely documenting burial related to
thrusting. Here we present new results from 40Ar/39Ar muscovite dating of ductile
to brittle shear zone on Prins Karls Forland, Svalbard, indicating Eurekan age of
thrusting.
Prins Karls Forland is dominated by Neoproterozoic siliciclastic metasediments
(comprising Caledonian basement) regionally metamorphosed to greenschist facies
conditions. A ∼1 km wide ductile to brittle shear zone (the Bouréefjellet shear zone)
separates the amphibolite facies Pinkie Unit from the lower grade upper structural
unit, the Grampianfjella Formation (Faehnrich et al. 2016, EGU 2016). The age
of the amphibolite facies metamorphism (c. 370-355 Ma) indicates Ellesmerian
tectonism, unlike other higher grade rocks on Svalbard (Kośmińska et al. 2016, EGU
2016).
Ten metasedimentary rocks from within the shear zone were collected for dating, with eight
muscovite crystals dated per sample via 40Ar/39Ar total fusion. High strain is evinced by
mylonitic fabric, mica fish or C’ shear zones. Moreover, quartz was dynamically
recrystallized with significant grain boundary migration. There is notable age dispersion
between the samples with weighted mean ages varying from 45 up to 103 Ma and single
grain ages are more than 300 Ma, reflecting partial recrystallization and resetting during
Eurekan deformation. Younger ages were obtained from lower structural levels, yielding
dates of 44 to 54 Ma for the Eurekan deformation on Prins Karls Forland. We suggest that an
Ellesmerian ductile shear zone was reactivated during Eocene (commencing as
early as 54 Ma) progressing to brittle conditions which continued after 44 Ma.
These are the first documented Eurekan 40Ar/39Ar muscovite deformation ages
from Svalbard, and enable to better distinguish individual stages of the Eurekan
deformation in the Eocene improving our understanding of relative plate tectonic
movements.
This work is partially funded by AGH research grant no 11.11.140.319 and the NCN research
projects 2013/11/N/ST10/00357 and 2015/17/B/ST10/03114. |
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