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Paleomagnetic study of NeoArchean-Paleoproterozoic dykes in the Kaapvaal Craton

Lubnina, Natalia; Ernst, Richard; Klausen, Martin and Söderlund, Ulf LU (2010) In Precambrian Research 183(3). p.523-552
Abstract
431 oriented samples were collected from 27 dolerite dykes at 17 sites, belonging to 2.95, 2.65, and 1.90 Ga swarms, that trend SE, E and NE, respectively from the Bushveld Igneous Complex into the eastern Kaapvaal Craton (ages determined by Olsson et al., 2010; Olsson in Soderlund et al., this volume). Samples were analyzed for paleomagnetism and also anisotropy of magnetic susceptibility (AMS). For the 2.95 Ga SE-trending dykes high temperature/coercivity 'P' component has unblocking temperatures up to 590 degrees C and coercivity 40-90 mT and demonstrate SSW declination and intermediate positive inclination. Based on positive contact and conglomerate tests we argue for a primary origin of this component. The paleopole (BAD), calculated... (More)
431 oriented samples were collected from 27 dolerite dykes at 17 sites, belonging to 2.95, 2.65, and 1.90 Ga swarms, that trend SE, E and NE, respectively from the Bushveld Igneous Complex into the eastern Kaapvaal Craton (ages determined by Olsson et al., 2010; Olsson in Soderlund et al., this volume). Samples were analyzed for paleomagnetism and also anisotropy of magnetic susceptibility (AMS). For the 2.95 Ga SE-trending dykes high temperature/coercivity 'P' component has unblocking temperatures up to 590 degrees C and coercivity 40-90 mT and demonstrate SSW declination and intermediate positive inclination. Based on positive contact and conglomerate tests we argue for a primary origin of this component. The paleopole (BAD), calculated from component, does not correspond to any of the previously obtained Archean-Paleoproterozoic paleopoles for the Kaapvaal Craton, and represents a new key pole for 2.95 Ga. The high-coercivity 'H' component for the 2.65 Ga-old E-trending dykes has a SSW declination and steep positive inclination. Paleomagnetic pole (RYK), recalculated from this component, is close to the paleopoles, obtained by Wingate (1998) and Strik et al. (2007) for 2.78 Ga Ventersdorp volcanics. The third group, NE-trending dykes of the 1.90 Ga Black Hill swarm demonstrate an 'M' component with dual polarity high-coercivity component with SSE-declination and negative intermediate inclination. The paleopole (BHD), calculated from this component is close to the 1.87 Ga pole of the Kaapvaal Craton obtained by Hanson et al. (2004). Overprint directions include a very well developed thermo-chemical overprint (Dec = 329 degrees Inc = -36 degrees), which is believed to be associated with a similar to 0.18 Ga regional 'Karoo' thermal event. (C) 2010 Elsevier B.V. All rights reserved. (Less)
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Contribution to journal
publication status
published
subject
keywords
dating, Baddeleyite, U-Pb, Kaapvaal Craton, Paleomagnetism, NeoArchean-Paleoproterozoic
in
Precambrian Research
volume
183
issue
3
pages
523 - 552
publisher
Elsevier
external identifiers
  • wos:000285233200012
  • scopus:78449284620
ISSN
0301-9268
DOI
10.1016/j.precamres.2010.05.005
language
English
LU publication?
yes
id
842aae20-02c5-4b71-929c-efb37b801825 (old id 1772405)
date added to LUP
2011-02-02 20:33:42
date last changed
2018-05-29 10:43:55
@article{842aae20-02c5-4b71-929c-efb37b801825,
  abstract     = {431 oriented samples were collected from 27 dolerite dykes at 17 sites, belonging to 2.95, 2.65, and 1.90 Ga swarms, that trend SE, E and NE, respectively from the Bushveld Igneous Complex into the eastern Kaapvaal Craton (ages determined by Olsson et al., 2010; Olsson in Soderlund et al., this volume). Samples were analyzed for paleomagnetism and also anisotropy of magnetic susceptibility (AMS). For the 2.95 Ga SE-trending dykes high temperature/coercivity 'P' component has unblocking temperatures up to 590 degrees C and coercivity 40-90 mT and demonstrate SSW declination and intermediate positive inclination. Based on positive contact and conglomerate tests we argue for a primary origin of this component. The paleopole (BAD), calculated from component, does not correspond to any of the previously obtained Archean-Paleoproterozoic paleopoles for the Kaapvaal Craton, and represents a new key pole for 2.95 Ga. The high-coercivity 'H' component for the 2.65 Ga-old E-trending dykes has a SSW declination and steep positive inclination. Paleomagnetic pole (RYK), recalculated from this component, is close to the paleopoles, obtained by Wingate (1998) and Strik et al. (2007) for 2.78 Ga Ventersdorp volcanics. The third group, NE-trending dykes of the 1.90 Ga Black Hill swarm demonstrate an 'M' component with dual polarity high-coercivity component with SSE-declination and negative intermediate inclination. The paleopole (BHD), calculated from this component is close to the 1.87 Ga pole of the Kaapvaal Craton obtained by Hanson et al. (2004). Overprint directions include a very well developed thermo-chemical overprint (Dec = 329 degrees Inc = -36 degrees), which is believed to be associated with a similar to 0.18 Ga regional 'Karoo' thermal event. (C) 2010 Elsevier B.V. All rights reserved.},
  author       = {Lubnina, Natalia and Ernst, Richard and Klausen, Martin and Söderlund, Ulf},
  issn         = {0301-9268},
  keyword      = {dating,Baddeleyite,U-Pb,Kaapvaal Craton,Paleomagnetism,NeoArchean-Paleoproterozoic},
  language     = {eng},
  number       = {3},
  pages        = {523--552},
  publisher    = {Elsevier},
  series       = {Precambrian Research},
  title        = {Paleomagnetic study of NeoArchean-Paleoproterozoic dykes in the Kaapvaal Craton},
  url          = {http://dx.doi.org/10.1016/j.precamres.2010.05.005},
  volume       = {183},
  year         = {2010},
}