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Baddeleyite geochronology and geochemistry of mafic cobbles from the Dwyka diamictite: New insights into the sub-Kalahari basement, South Africa

van Schijndel, Valby; Cornell, David H.; Karlsson, Linn and Olsson, Johan LU (2011) In Lithos 126(3-4). p.307-320
Abstract
U-Pb baddeleyite geochronology and geochemistry of mafic cobbles from the similar to 300 Ma Dwyka diamictite on the western boundary of the Kalahari Basin provide new insights into the sub-Kalahari basement. Palaeo-ice flow directions indicate that the origin of the Dwyka diamictite deposits on the border between South Africa and Namibia is from beneath the Kalahari sands to the east or north-east. This work shows that the mafic cobbles from three localities near Rietfontein come from intrusions related to the Umkondo Large Igneous Province (LIP), located in the Kheis or Rehoboth Provinces. The lack of Banded Iron Formation (BIF) cobbles in these glacial diamictites indicates that their source region lies west or north of the BIF-dominated... (More)
U-Pb baddeleyite geochronology and geochemistry of mafic cobbles from the similar to 300 Ma Dwyka diamictite on the western boundary of the Kalahari Basin provide new insights into the sub-Kalahari basement. Palaeo-ice flow directions indicate that the origin of the Dwyka diamictite deposits on the border between South Africa and Namibia is from beneath the Kalahari sands to the east or north-east. This work shows that the mafic cobbles from three localities near Rietfontein come from intrusions related to the Umkondo Large Igneous Province (LIP), located in the Kheis or Rehoboth Provinces. The lack of Banded Iron Formation (BIF) cobbles in these glacial diamictites indicates that their source region lies west or north of the BIF-dominated Griqualand West Basin of the Kaapvaal Craton. The four dated mafic cobbles give U-Pb ages of 1111-1123 Ma, coeval with dolerites of the Umkondo LIP. The cobbles experienced greenschist fades metamorphism before the Dwyka glaciation, but are unfoliated. The geochemistry of the cobbles indicates that they are genetically similar and have a within-plate setting. They show many similarities to the Umkondo LIP dolerites and the coeval Rouxville Formation, an upper unit of the Koras Group. The most likely sources of the cobbles are the mafic intrusives and lavas along the Kalahari Line, southern equivalents of the similar to 1.11 Ga Tshane and Xade complexes or intrusive and extrusive mafic units related to the Umkondo LIP, now concealed beneath the Kalahari sands. (C) 2011 Elsevier By. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Dwyka diamictite, U-Pb baddeleyite geochronology, Geochemistry, Umkondo, LIP, Koras group
in
Lithos
volume
126
issue
3-4
pages
307 - 320
publisher
Elsevier
external identifiers
  • wos:000296822900013
  • scopus:80052026853
ISSN
0024-4937
DOI
10.1016/j.lithos.2011.07.019
language
English
LU publication?
yes
id
a405e723-6f74-4c6b-812b-01c0f4f4223f (old id 2253157)
date added to LUP
2011-12-21 15:28:50
date last changed
2017-01-01 03:24:01
@article{a405e723-6f74-4c6b-812b-01c0f4f4223f,
  abstract     = {U-Pb baddeleyite geochronology and geochemistry of mafic cobbles from the similar to 300 Ma Dwyka diamictite on the western boundary of the Kalahari Basin provide new insights into the sub-Kalahari basement. Palaeo-ice flow directions indicate that the origin of the Dwyka diamictite deposits on the border between South Africa and Namibia is from beneath the Kalahari sands to the east or north-east. This work shows that the mafic cobbles from three localities near Rietfontein come from intrusions related to the Umkondo Large Igneous Province (LIP), located in the Kheis or Rehoboth Provinces. The lack of Banded Iron Formation (BIF) cobbles in these glacial diamictites indicates that their source region lies west or north of the BIF-dominated Griqualand West Basin of the Kaapvaal Craton. The four dated mafic cobbles give U-Pb ages of 1111-1123 Ma, coeval with dolerites of the Umkondo LIP. The cobbles experienced greenschist fades metamorphism before the Dwyka glaciation, but are unfoliated. The geochemistry of the cobbles indicates that they are genetically similar and have a within-plate setting. They show many similarities to the Umkondo LIP dolerites and the coeval Rouxville Formation, an upper unit of the Koras Group. The most likely sources of the cobbles are the mafic intrusives and lavas along the Kalahari Line, southern equivalents of the similar to 1.11 Ga Tshane and Xade complexes or intrusive and extrusive mafic units related to the Umkondo LIP, now concealed beneath the Kalahari sands. (C) 2011 Elsevier By. All rights reserved.},
  author       = {van Schijndel, Valby and Cornell, David H. and Karlsson, Linn and Olsson, Johan},
  issn         = {0024-4937},
  keyword      = {Dwyka diamictite,U-Pb baddeleyite geochronology,Geochemistry,Umkondo,LIP,Koras group},
  language     = {eng},
  number       = {3-4},
  pages        = {307--320},
  publisher    = {Elsevier},
  series       = {Lithos},
  title        = {Baddeleyite geochronology and geochemistry of mafic cobbles from the Dwyka diamictite: New insights into the sub-Kalahari basement, South Africa},
  url          = {http://dx.doi.org/10.1016/j.lithos.2011.07.019},
  volume       = {126},
  year         = {2011},
}