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Extending the time range of apatite (U-Th)/He thermochronometry in slowly cooled terranes: Palaeozoic to Cenozoic exhumation history of southeast Sweden

Söderlund, Pia LU ; Juez-Larre, J; Page, Laurence LU and Dunai, TJ (2005) In Earth and Planetary Science Letters 239(3-4). p.266-275
Abstract
The use of (U-Th)/He thermochronometry in old slowly cooled terranes has long been debated. Hence, studies of natural setting are needed to verify the expected diffusivity behaviour of helium. Our results demonstrate that the (U-Th)/He method can be applicable to samples older than 200 Ma, and that available helium diffusion models can reproduce the results obtained from the age-vs.-depth trends. In addition, the results shed some light on the cross-validation with the apatite fission-track thermochronometer. (U-Th)/He thermochronometry on apatites has been applied to samples taken from drill cores in the Precambrian basement in southeast Sweden to unravel the time of exhumation of the uppermost 1-3 km of the crust. Much of the Phanerozoic... (More)
The use of (U-Th)/He thermochronometry in old slowly cooled terranes has long been debated. Hence, studies of natural setting are needed to verify the expected diffusivity behaviour of helium. Our results demonstrate that the (U-Th)/He method can be applicable to samples older than 200 Ma, and that available helium diffusion models can reproduce the results obtained from the age-vs.-depth trends. In addition, the results shed some light on the cross-validation with the apatite fission-track thermochronometer. (U-Th)/He thermochronometry on apatites has been applied to samples taken from drill cores in the Precambrian basement in southeast Sweden to unravel the time of exhumation of the uppermost 1-3 km of the crust. Much of the Phanerozoic exhumation history in Sweden is poorly constrained due to a large hiatus in the sediment record. Results from the drill cores yield He ages decreasing with increasing depth from similar to 270 Ma at the surface down to similar to 120 Ma at 1700 in depth. The age-vs.-depth trend shows an inflection point at similar to 1400 in depth, which coincides with the upper boundary of the present Helium Partial Retention Zone. A period of slow exhumation (similar to 17 m/my), probably linked to the isostatic uplift of the Caledonian foreland basin, is revealed by the upper section of the trend in the data. The results demonstrate that the area has not been reheated since the mid-Permian. This argues against the existence of a thick Mesozoic sedimentary cover in this region, which, if present at all, cannot have exceeded 100 in in thickness. Furthermore, the age-vs.-depth trend below the inflection point allows dating the cessation of exhumation at approximately 100 Ma. The area has had no significant amount of sedimentation, erosion or uplift since this time. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Sweden, Caledonian foreland basin, apatite, (U-Th)/He thermochronology, Baltic Shield
in
Earth and Planetary Science Letters
volume
239
issue
3-4
pages
266 - 275
publisher
Elsevier
external identifiers
  • wos:000233323400007
  • scopus:27744496567
ISSN
1385-013X
DOI
10.1016/j.epsl.2005.09.009
language
English
LU publication?
yes
id
32c5027e-138b-427a-8709-662913ed6f8f (old id 213231)
date added to LUP
2007-08-13 09:33:12
date last changed
2017-08-27 03:54:44
@article{32c5027e-138b-427a-8709-662913ed6f8f,
  abstract     = {The use of (U-Th)/He thermochronometry in old slowly cooled terranes has long been debated. Hence, studies of natural setting are needed to verify the expected diffusivity behaviour of helium. Our results demonstrate that the (U-Th)/He method can be applicable to samples older than 200 Ma, and that available helium diffusion models can reproduce the results obtained from the age-vs.-depth trends. In addition, the results shed some light on the cross-validation with the apatite fission-track thermochronometer. (U-Th)/He thermochronometry on apatites has been applied to samples taken from drill cores in the Precambrian basement in southeast Sweden to unravel the time of exhumation of the uppermost 1-3 km of the crust. Much of the Phanerozoic exhumation history in Sweden is poorly constrained due to a large hiatus in the sediment record. Results from the drill cores yield He ages decreasing with increasing depth from similar to 270 Ma at the surface down to similar to 120 Ma at 1700 in depth. The age-vs.-depth trend shows an inflection point at similar to 1400 in depth, which coincides with the upper boundary of the present Helium Partial Retention Zone. A period of slow exhumation (similar to 17 m/my), probably linked to the isostatic uplift of the Caledonian foreland basin, is revealed by the upper section of the trend in the data. The results demonstrate that the area has not been reheated since the mid-Permian. This argues against the existence of a thick Mesozoic sedimentary cover in this region, which, if present at all, cannot have exceeded 100 in in thickness. Furthermore, the age-vs.-depth trend below the inflection point allows dating the cessation of exhumation at approximately 100 Ma. The area has had no significant amount of sedimentation, erosion or uplift since this time.},
  author       = {Söderlund, Pia and Juez-Larre, J and Page, Laurence and Dunai, TJ},
  issn         = {1385-013X},
  keyword      = {Sweden,Caledonian foreland basin,apatite,(U-Th)/He thermochronology,Baltic Shield},
  language     = {eng},
  number       = {3-4},
  pages        = {266--275},
  publisher    = {Elsevier},
  series       = {Earth and Planetary Science Letters},
  title        = {Extending the time range of apatite (U-Th)/He thermochronometry in slowly cooled terranes: Palaeozoic to Cenozoic exhumation history of southeast Sweden},
  url          = {http://dx.doi.org/10.1016/j.epsl.2005.09.009},
  volume       = {239},
  year         = {2005},
}