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New U–Pb age and paleomagnetic constraints from the Uitkomst Complex, South Africa : clues to the timing of intrusion

Wabo, H.; Olsson, Johan LU ; de Kock, M. O.; Humbert, F.; Söderlund, U. LU and Klausen, M. B. (2016) In GFF 138(1). p.152-163
Abstract

The Uitkomst Complex is considered to be coeval with, and genetically linked to the Rustenburg Layered Suite (RLS) of the Bushveld Large Igneous Province. This study reports new paleomagnetic, geochemical and geochronological results from the Uitkomst Complex and a crosscutting dyke at the Nkomati Mine. Primary magnetisations for the complex and the dyke are statistically indistinguishable. This, together with the geochemical signature of the dyke, suggests a late-magmatic link with the Uitkomst Complex. A Virtual Geomagnetic Pole calculated for the complex at Longitude 28.7°N and Latitude 58.5°E (dp = 6.2; dm = 9.4; N = 3) differs from the 1900 Ma and younger-aged poles for the Kaapvaal Craton. It, however, shares similarities with the... (More)

The Uitkomst Complex is considered to be coeval with, and genetically linked to the Rustenburg Layered Suite (RLS) of the Bushveld Large Igneous Province. This study reports new paleomagnetic, geochemical and geochronological results from the Uitkomst Complex and a crosscutting dyke at the Nkomati Mine. Primary magnetisations for the complex and the dyke are statistically indistinguishable. This, together with the geochemical signature of the dyke, suggests a late-magmatic link with the Uitkomst Complex. A Virtual Geomagnetic Pole calculated for the complex at Longitude 28.7°N and Latitude 58.5°E (dp = 6.2; dm = 9.4; N = 3) differs from the 1900 Ma and younger-aged poles for the Kaapvaal Craton. It, however, shares similarities with the poles from the 2058 to 2054 Ma RLS and other ~2.0 Ga paleopoles for the Kaapvaal Craton. Moreover, a new U–Pb baddeleyite age of 2054 ± 7 Ma given by a coarse-grained gabbroic sample from Nkomati’s underground mine provides a minimum age constraint on the crystallisation of the Uitkomst Complex. This date is nominally older than the 207Pb/206Pb zircon age of 2044 ± 8 Ma previously reported for this complex, and also near identical to the new age of 2054.89 ± 0.37 Ma from the Critical Zone of the RLS. Here, it is suggested that the Uitkomst Complex was emplaced at the same time as, if not before the Critical Zone. Data presented here have bearings on the location of the Uitkomst Complex in the time frame model recently proposed for the Bushveld magmatism.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bushveld magmatism, Kaapvaal Craton, paleomagnetism, Uitkomst Complex, U–Pb baddeleyite dating
in
GFF
volume
138
issue
1
pages
12 pages
publisher
Geological Society of Sweden
external identifiers
  • Scopus:84959094779
ISSN
1103-5897
DOI
10.1080/11035897.2015.1098726
language
English
LU publication?
yes
id
f8f7494a-f5aa-4bb0-9a0c-3fc7de2979c8
date added to LUP
2016-09-20 14:56:58
date last changed
2016-09-20 14:56:58
@misc{f8f7494a-f5aa-4bb0-9a0c-3fc7de2979c8,
  abstract     = {<p>The Uitkomst Complex is considered to be coeval with, and genetically linked to the Rustenburg Layered Suite (RLS) of the Bushveld Large Igneous Province. This study reports new paleomagnetic, geochemical and geochronological results from the Uitkomst Complex and a crosscutting dyke at the Nkomati Mine. Primary magnetisations for the complex and the dyke are statistically indistinguishable. This, together with the geochemical signature of the dyke, suggests a late-magmatic link with the Uitkomst Complex. A Virtual Geomagnetic Pole calculated for the complex at Longitude 28.7°N and Latitude 58.5°E (dp = 6.2; dm = 9.4; N = 3) differs from the 1900 Ma and younger-aged poles for the Kaapvaal Craton. It, however, shares similarities with the poles from the 2058 to 2054 Ma RLS and other ~2.0 Ga paleopoles for the Kaapvaal Craton. Moreover, a new U–Pb baddeleyite age of 2054 ± 7 Ma given by a coarse-grained gabbroic sample from Nkomati’s underground mine provides a minimum age constraint on the crystallisation of the Uitkomst Complex. This date is nominally older than the <sup>207</sup>Pb/<sup>206</sup>Pb zircon age of 2044 ± 8 Ma previously reported for this complex, and also near identical to the new age of 2054.89 ± 0.37 Ma from the Critical Zone of the RLS. Here, it is suggested that the Uitkomst Complex was emplaced at the same time as, if not before the Critical Zone. Data presented here have bearings on the location of the Uitkomst Complex in the time frame model recently proposed for the Bushveld magmatism.</p>},
  author       = {Wabo, H. and Olsson, Johan and de Kock, M. O. and Humbert, F. and Söderlund, U. and Klausen, M. B.},
  issn         = {1103-5897},
  keyword      = {Bushveld magmatism,Kaapvaal Craton,paleomagnetism,Uitkomst Complex,U–Pb baddeleyite dating},
  language     = {eng},
  month        = {01},
  number       = {1},
  pages        = {152--163},
  publisher    = {ARRAY(0x83b06e8)},
  series       = {GFF},
  title        = {New U–Pb age and paleomagnetic constraints from the Uitkomst Complex, South Africa : clues to the timing of intrusion},
  url          = {http://dx.doi.org/10.1080/11035897.2015.1098726},
  volume       = {138},
  year         = {2016},
}