Advanced

Precise U-Pb ages and geochemistry of Palaeoproterozoic mafic dykes from southern West Greenland: Linking the North Atlantic and the Dharwar cratons

Nilsson, Mimmi LU ; Klausen, M. B. ; Söderlund, Ulf LU and Ernst, R. E. (2013) In Lithos 174. p.255-270
Abstract
Palaeoproterozoic magmatism throughout the North Atlantic Craton (NAC) has produced dyke swarms of diverse orientations and emplacement ages. In southern West Greenland, previously identified swarms include the ca. 2500 Ma Kilarsaarfik dykes, ca. 2215 Ma boninitic norite (BN) dykes, and the abundant ca. 2040 Ma Kangamiut and coeval 2050-2030 Ma MD3 dykes. Additional insight into the distribution of swarms is provided by new baddeleyite U-Pb ID-TIMS dates interpreted as emplacement ages for six dykes. The geochemistry for a total of 42 samples on 40 dykes (including the dated dykes) provides some constraints on their petrogenesis. Two E-W trending dykes yield ages of 2365 +/- 2 Ma and 2374 +/- 4 Ma, representing a hitherto unknown magmatic... (More)
Palaeoproterozoic magmatism throughout the North Atlantic Craton (NAC) has produced dyke swarms of diverse orientations and emplacement ages. In southern West Greenland, previously identified swarms include the ca. 2500 Ma Kilarsaarfik dykes, ca. 2215 Ma boninitic norite (BN) dykes, and the abundant ca. 2040 Ma Kangamiut and coeval 2050-2030 Ma MD3 dykes. Additional insight into the distribution of swarms is provided by new baddeleyite U-Pb ID-TIMS dates interpreted as emplacement ages for six dykes. The geochemistry for a total of 42 samples on 40 dykes (including the dated dykes) provides some constraints on their petrogenesis. Two E-W trending dykes yield ages of 2365 +/- 2 Ma and 2374 +/- 4 Ma, representing a hitherto unknown magmatic event. We propose the name Graedefjord dykes for dykes of this age in southern West Greenland. One NE-SW trending dyke is dated at 2209 +/- 5 Ma, close to a previously published 2214 +/- 10 Ma age for a N-S trending dyke (member of BN dykes). Three dykes yield MD3 ages of 2053 +/- 2 Ma (E-W trending), 2049 +/- 6 Ma (N-S trending) and 2042 +/- 2 Ma (WNW-ESE trending). Ca. 2.21 Ga old and predominantly NE-SE and NNE-SSE trending dolerites (some of which are high-Al basalts) were derived from a relatively depleted mantle and injected during a boninite-dolerite magmatic event, together with nearby BN dykes derived from a harzburgitic, yet highly LREE and LILE enriched, subcontinental lithospheric mantle (SCLM). Ca. 2.05 Ga Kangamiut-MD3 dolerites were derived from a similar ambient asthenospheric mantle and subsequently experienced crustal assimilation during fractional crystallisation. The ca. 2370 Ma dykes in the NAC are coeval with the Dharwar Giant Dyke Swarm of the Dharwar Craton (DC) and based on this unique age match it is proposed that the Dharwar and NAC were neighbours in the Palaeoproterozoic. Furthermore, both blocks share 222-2.21 Ga dykes, and matching the trends of 2.2-2.1 and 2.37 Ga swarms between the two blocks allows several plausible reconstructions. (C) 2012 Published by Elsevier B.V. (Less)
Please use this url to cite or link to this publication:
author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
North Atlantic Craton, Dharwar Craton, U-Pb, Baddeleyite, Mafic dykes, Palaeoproterozoic
in
Lithos
volume
174
pages
255 - 270
publisher
Elsevier
external identifiers
  • wos:000321680400018
  • scopus:84878953850
ISSN
0024-4937
DOI
10.1016/j.lithos.2012.07.021
language
English
LU publication?
yes
id
7cf2e6d3-4e9a-46eb-8538-94787a46e355 (old id 3975658)
date added to LUP
2016-04-01 09:57:40
date last changed
2020-12-27 04:40:16
@article{7cf2e6d3-4e9a-46eb-8538-94787a46e355,
  abstract     = {Palaeoproterozoic magmatism throughout the North Atlantic Craton (NAC) has produced dyke swarms of diverse orientations and emplacement ages. In southern West Greenland, previously identified swarms include the ca. 2500 Ma Kilarsaarfik dykes, ca. 2215 Ma boninitic norite (BN) dykes, and the abundant ca. 2040 Ma Kangamiut and coeval 2050-2030 Ma MD3 dykes. Additional insight into the distribution of swarms is provided by new baddeleyite U-Pb ID-TIMS dates interpreted as emplacement ages for six dykes. The geochemistry for a total of 42 samples on 40 dykes (including the dated dykes) provides some constraints on their petrogenesis. Two E-W trending dykes yield ages of 2365 +/- 2 Ma and 2374 +/- 4 Ma, representing a hitherto unknown magmatic event. We propose the name Graedefjord dykes for dykes of this age in southern West Greenland. One NE-SW trending dyke is dated at 2209 +/- 5 Ma, close to a previously published 2214 +/- 10 Ma age for a N-S trending dyke (member of BN dykes). Three dykes yield MD3 ages of 2053 +/- 2 Ma (E-W trending), 2049 +/- 6 Ma (N-S trending) and 2042 +/- 2 Ma (WNW-ESE trending). Ca. 2.21 Ga old and predominantly NE-SE and NNE-SSE trending dolerites (some of which are high-Al basalts) were derived from a relatively depleted mantle and injected during a boninite-dolerite magmatic event, together with nearby BN dykes derived from a harzburgitic, yet highly LREE and LILE enriched, subcontinental lithospheric mantle (SCLM). Ca. 2.05 Ga Kangamiut-MD3 dolerites were derived from a similar ambient asthenospheric mantle and subsequently experienced crustal assimilation during fractional crystallisation. The ca. 2370 Ma dykes in the NAC are coeval with the Dharwar Giant Dyke Swarm of the Dharwar Craton (DC) and based on this unique age match it is proposed that the Dharwar and NAC were neighbours in the Palaeoproterozoic. Furthermore, both blocks share 222-2.21 Ga dykes, and matching the trends of 2.2-2.1 and 2.37 Ga swarms between the two blocks allows several plausible reconstructions. (C) 2012 Published by Elsevier B.V.},
  author       = {Nilsson, Mimmi and Klausen, M. B. and Söderlund, Ulf and Ernst, R. E.},
  issn         = {0024-4937},
  language     = {eng},
  pages        = {255--270},
  publisher    = {Elsevier},
  series       = {Lithos},
  title        = {Precise U-Pb ages and geochemistry of Palaeoproterozoic mafic dykes from southern West Greenland: Linking the North Atlantic and the Dharwar cratons},
  url          = {http://dx.doi.org/10.1016/j.lithos.2012.07.021},
  doi          = {10.1016/j.lithos.2012.07.021},
  volume       = {174},
  year         = {2013},
}