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U–Pb baddeleyite geochronology and geochemistry of the White Mfolozi Dyke Swarm : unravelling the complexities of 2.70–2.66 Ga dyke swarms across the eastern Kaapvaal Craton, South Africa

Gumsley, Ashley LU ; Rådman, Johan; Söderlund, Ulf LU and Klausen, Martin (2016) In GFF 138(1). p.115-132
Abstract

On the south-easternmost Kaapvaal Craton, a NE-trending plagioclase-megacrystic dolerite dyke swarm, herein named the White Mfolozi Dyke Swarm (WMDS), has been identified. New U–Pb baddeleyite ages presented here indicate that the WMDS was emplaced within less than 10 million years, with our three most robust results yielding a weighted mean age of 2662 ± 2 Ma. The WMDS is coeval with the youngest dykes of a 2.70–2.66 Ga radiating dyke swarm already identified further north on the eastern side of the Kaapvaal Craton. This dyke swarm radiates out from the eastern lobe of the ca. 2.05 Ga Bushveld Complex. A clustering of ages from the WMDS and the 2.70–2.66 Ga radiating dyke swarm identify potential magmatic peaks at 2701–2692 Ma,... (More)

On the south-easternmost Kaapvaal Craton, a NE-trending plagioclase-megacrystic dolerite dyke swarm, herein named the White Mfolozi Dyke Swarm (WMDS), has been identified. New U–Pb baddeleyite ages presented here indicate that the WMDS was emplaced within less than 10 million years, with our three most robust results yielding a weighted mean age of 2662 ± 2 Ma. The WMDS is coeval with the youngest dykes of a 2.70–2.66 Ga radiating dyke swarm already identified further north on the eastern side of the Kaapvaal Craton. This dyke swarm radiates out from the eastern lobe of the ca. 2.05 Ga Bushveld Complex. A clustering of ages from the WMDS and the 2.70–2.66 Ga radiating dyke swarm identify potential magmatic peaks at 2701–2692 Ma, 2686–2683 Ma and 2665–2659 Ma. Geochemical signatures of the dykes do not correlate with these age groups, but are rather unique to specific areas. The northern part of the eastern Kaapvaal Craton hosts relatively differentiated 2.70–2.66 Ga dolerite dykes that could have been derived from a moderately enriched mantle source, whereas the ca. 2.66 Ga WMDS from the southernmost area exhibit much more depleted signatures. In between these two margins, the central area hosts more andesitic 2.70–2.66 Ga dykes that may have assimilated substantial amounts of partly digested tonalite–trondhjemite–granodiorite crust from the basement. We investigate the evolution for the Kaapvaal Craton during a highly magmatic period that extends for over 60 million years from extensive Ventersdorp volcanism to the eruption of proto-basinal volcanic rocks at the base of the Transvaal Supergroup.

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organization
publishing date
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Contribution to journal
publication status
published
subject
keywords
geochemistry, Kaapvaal Craton, U–Pb baddeleyite geochronology, White Mfolozi Dyke Swarm
in
GFF
volume
138
issue
1
pages
18 pages
publisher
Geological Society of Sweden
external identifiers
  • scopus:84959078836
  • wos:000371812700009
ISSN
1103-5897
DOI
10.1080/11035897.2015.1122665
language
English
LU publication?
yes
id
dd0c926e-a8e7-499a-8ac4-29fb41e4e15c
date added to LUP
2016-09-20 13:39:47
date last changed
2017-03-05 04:36:25
@article{dd0c926e-a8e7-499a-8ac4-29fb41e4e15c,
  abstract     = {<p>On the south-easternmost Kaapvaal Craton, a NE-trending plagioclase-megacrystic dolerite dyke swarm, herein named the White Mfolozi Dyke Swarm (WMDS), has been identified. New U–Pb baddeleyite ages presented here indicate that the WMDS was emplaced within less than 10 million years, with our three most robust results yielding a weighted mean age of 2662 ± 2 Ma. The WMDS is coeval with the youngest dykes of a 2.70–2.66 Ga radiating dyke swarm already identified further north on the eastern side of the Kaapvaal Craton. This dyke swarm radiates out from the eastern lobe of the ca. 2.05 Ga Bushveld Complex. A clustering of ages from the WMDS and the 2.70–2.66 Ga radiating dyke swarm identify potential magmatic peaks at 2701–2692 Ma, 2686–2683 Ma and 2665–2659 Ma. Geochemical signatures of the dykes do not correlate with these age groups, but are rather unique to specific areas. The northern part of the eastern Kaapvaal Craton hosts relatively differentiated 2.70–2.66 Ga dolerite dykes that could have been derived from a moderately enriched mantle source, whereas the ca. 2.66 Ga WMDS from the southernmost area exhibit much more depleted signatures. In between these two margins, the central area hosts more andesitic 2.70–2.66 Ga dykes that may have assimilated substantial amounts of partly digested tonalite–trondhjemite–granodiorite crust from the basement. We investigate the evolution for the Kaapvaal Craton during a highly magmatic period that extends for over 60 million years from extensive Ventersdorp volcanism to the eruption of proto-basinal volcanic rocks at the base of the Transvaal Supergroup.</p>},
  author       = {Gumsley, Ashley and Rådman, Johan and Söderlund, Ulf and Klausen, Martin},
  issn         = {1103-5897},
  keyword      = {geochemistry,Kaapvaal Craton,U–Pb baddeleyite geochronology,White Mfolozi Dyke Swarm},
  language     = {eng},
  month        = {01},
  number       = {1},
  pages        = {115--132},
  publisher    = {Geological Society of Sweden},
  series       = {GFF},
  title        = {U–Pb baddeleyite geochronology and geochemistry of the White Mfolozi Dyke Swarm : unravelling the complexities of 2.70–2.66 Ga dyke swarms across the eastern Kaapvaal Craton, South Africa},
  url          = {http://dx.doi.org/10.1080/11035897.2015.1122665},
  volume       = {138},
  year         = {2016},
}